CA1275231C - Capillary flow device - Google Patents

Abstract

CAPILLARY FLOW DEVICE
ABSTRACT OF THE DISCLOSURE
Novel methods and devices are provided involving at least one chamber, at least one capillary, and at least one reagent involved in a system providing for a detectable signal. As appropriate, the devices provide for measuring a sample, mixing the sample with reagents, defining a flow path, and reading the result.
Of particular interest is the use of combinations of specific binding pair members which result in agglutination information, where the resulting agglutination particles may provide for changes in flow rate, light patterns of a flowing medium, or light absorption or scattering. A fabrication technique particularly suited for forming internal chambers in plastic devices is also described along with various control devices for use with the basic device.

Description

CAPILLARY FLOW DE~ICE
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This invention is related to te ting device~
having internal chambers into whlch fluids are drawn by capillary action, to methods o~ using such devices, and to methods of manufacturlng ~uch devices.

In the development of the diagnostic~ field, there ha3 been explo~ive growth in the number of substances to be determlned. For the mo~t part, the medical rield has looked to clinical laboratories ror the~e determination~. The clinical laboratorie~ have been dependent upon expen3ive ~ophi~ticated equipment and highly trained technical help to ful~ill the , ~ani~old need~ o~ the medical community. However, in a highly automated clinical laboratory, there i~
substantial need to perform one or a rew a~say3 on a ~tat ba3i3 with mlnimum equipment.
There i3 al~o an expanding need for having analytical capabilities in doctors' of~ices and in the home. There is a continuing need to monitor the level o~ dru~ admini~tered to people with chronic illnesses, ~uch a~ dlabeticq, asthmatics, epileptics, and cardiac patients, as lt appear~ in a phy~iological ~luid, 3uch as blood. Test~ of interest lnclude prothrombln tlme, po~a~sium ion, and cholesterol. Determining red-blood-cell count lq al~Q a common teqt~ In the ca~e o~
dia~e~ic patlents, lt is necessary to determlne sugar le~el in urine or blood.
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Numerou3 approaches have been developed toward this end, depending to varying degrees on in~trumental or visual ob ervation of the result.
Typical of these are the 30 called "dip-stick"
5 method~. The~e methods generally employ a pla~tic ~trip with a reagent-containing matrix layered thereon. Sample i~ applied to the strip and the presence or absence o~ a analyte is indicated by a color-forming reaction. ~hile ~uch devices have proven 10 u~eful ~or the qualitative determination of the presence of analyte~ in urine and can even be u~ed for rough quantitative analysis, they are not particularly useful w~th whole blood because of the interferring effects of red blood cells, nor are they useful ~or 5 making fine quantitative distinction~. Accordingly, there remains a need for the development of method~ and devices capable o~ analyzing whole blood and other complex ~amples rapidly with a minimum of user manipulation~.
Many ~mall device~ in the analytical area depend on the use of plaqtics having specified characteri3tics, such as optical transparency and machinability. Machinability refers here to the ability to produce chamber~, channel~, and openings o~
25 prescribed dlmensions within the pla~tic de~ice.
Although numerous pla~tic devices have been devi3ed, the fabricatlon technique~ are not interchangeable becau3e o~ di~ference~ in She devices or the de~ired measuring result. This i~ partlcularly true for 3 device~ containing channel3 or other chamber~ of small dimen~ions internally in the plaqtic material. The ~ine channels are difficult to produce entirely within a plastlc matrix and, if prepared in the ~urface of two matrices to be sealed to each other, are readily de~ormed during many sealing proces~e~.

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Accordingly, there remain~ a need for new devices for u~e ln method of rapid analytical testing and for new methods o~ producing these devices.

Power~ et al., IEEE Trans._ on Biomedical En~r. t1983) BME-30-228, de3cribes deteoting a ~peckle pattern rcr determining platelet aggregation J a~ does Reynold3, Light Scattering Detection o~ Thromboemboli, Trans. 11th Annual Mtg. o~ the Soc. for Biomaterials, San Diego, CA, April 25-28, 1985. Reynolds and Simon, Transfuslon ~1980) 20:669-677, de~cribes size distribution ~aasurement~ of microaggregates in stored blood. 0~ intere~t ~n the 3ame area are U.S. Patent Nos. 2,616,796; 3,810,010; 3,915,652; 4,040,742;
4,091,802; and 4,142,796. U.S. Patent No. 4,519,239 de~cribes an apparatus for determining flow ~hear stress o~ suspen~ion~ in ~lood. Ab Leo sell3 the HemoCueTM device ~or mea~uring hemoglobin. Also, see U.S. Patent No. 4,088,448, which de~cribes a cuvette ~or ~ampllng with a cavity which i3 de~ined in ~uoh a manner a~ to draw into the cavity a sample in an amount which is exactly determined in relation to the volume Or the cavity by capillary rorce. Numerous pla~tlc as~embly techniques, particularly ultrasonic~ plastic asqembly, is described in a book of the same name publi~hed by Bran~on Sonic Power Company, Danbury, Connectiout, 1979. Gallagan, Plastics En~ineerin~, August 1985, 35-37 al~o de~cribes ultra~onLc welding Or pla9tic~. U.S. Patent 3,376,208 describes corona discharge, although ~or a different purpose. U~S.
Patent 3,376,208 describes the use of an electric dlschar~e to modi~y a film ~urface. A device used to transport liquids by capillary flow is described ln U.S. Patent 4, 233,029.

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' The present inventlon provldes fabricatlon techniques, the resulting devices, and techniques related to the use Or ~uch device~ ln which a defined chamber or channel i~ prepared within the internal space Or a ~olid device. The devices typically call ror the u~e o~ capillary ~orce to draw a sample into the internal chambers of a pla tic device. Such capillary flow devices, particularly capillary flow dev~ces designed for a constant ~low rate, typically lnclude at least one capillary acting as a pu~p, usually ror controlling the volume of the sample and the tlme period ~or reaction, a chamber, an lnlet port, a vent, and a reagent in proximity to at least one sur~ace of the devlce. The capillary and chamber provide rOr capillary flow due to sur~ace action and ~or mixing o~ the assay medium with the reagent. The reagent iq part o~ a detection system, whereby a detectable result occurs in relation to the pre-~ence of 2~ an analyte. The device and the corresponding method can be u~ed with a wide variety of ~luid3, particularly physiological fluids, for detection of drugs, pathogen~, material~ endogenou3 to a host, or the like. In mo~t ca3es an optical measurement 19 being ~ade, which requires the selection o~ a tran3parent material. Devices Or unusually advantageous properties can be prepared by in~ection molding acrylonitrile-butadiene-styrene copolymer tA~S) 90 as to form a depression Or defined dimenqion~ in the surface of at least one race Or the polymer, increasing wettability Or the ~urface ln at least those portion~ de~ined by the depression u~lng either plasma etching or corona discharge, providing energy directing ridges proJecting ~rom the sur~ace Or the plastic ad~acent to the depres3ion or ln a second piece Or plastic 90 3haped as to contact the area ad~acent to the depressions in the pla~tic surrac~, and ultrasonlcally weldlng the two . .

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pla3tic .qurfaces ao as to produce an internal chamber or channel o~ derined dlmen~ion~ having an air-tlght 3eal around the perimeter or the re~ulting chamber.
Although the rabrication method can be used to produce internal chambers o~ any dlmen~ion, the method i~
partlcularly ~uitable rOr the production Or chambers and channel~ of small dimen~ions that are 3uitable rOr inducing capillary flow.
Aspects of the invention are illustrated, merely by way of example, in the drawings, in which:

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Figures 1A and 1B are plan views Or two embodiments o~ the subject Lnvention, Flg. lA employing a single c~pillary and chamber and Fi8. 18 employing two capillarie ~eparated by a chamber~
Figure~ 2A and Z8 are a plan view and a ~ide elevational view o~ a device employlng three chambers.
Figure 3 is a plan view of a device ror a plurality of ~imultaneou~ determination~.
Figure 4 i-~ a plan vi0w o~ an alternate embodiment, where the sample i~ dLvided into two separate channel~.
Figure 5 is a plan vlew of an alternate t embodiment employing an extended capillary path.
Fisure 6 i~ a cross-~ectional view of an embodiment showing the location o~ channel~ and energy dlrecting ridges during the fabrication procesa.
Figure 7 i9 a block diagram oY an electronic circuit ~uitable for use ln an electronic capill~ry cartidge device to simulate the pas~age Or blood through a capillary in a control cycle.
Figure 8 ic a diagram of the physical location and electronlc circui~ry of a detector capable o~ determining depletion of sample ~n a re3ervoir Or a capillary deviGe.

Thi invention provide~ de~lces and methods, where the devices rely upon capillarie~, chambers, and orifice~ to pump rluid9; to control measurement o~
rluids, reaction times, and mixing Or reagents; and to determine a de~ectable ~ignal. By ~arylng the path through which the fluid flow~, one can provide ~or a Yarlety o~ activltie~, such as mixing, incubating and detectin~. The method~ may in~olve the binding ~f ha~olo~ou3 member~ oY a spQcl~ic binding palr, resultlng ln complex rormatlon. The complex rormation . :

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can provide for a variety o~ events which can be detected by instrumentation or vi~ual means.
Alternatively, the method~ may involve chemLcal reactions, ~or example, the detection Or glucose or erum en2ymes, which re3ult in a detectable change in the ~ample medium. Since the deYices rely upon capillarie~ and other chambers to control move~ent of fluids, accurate control o~ the dimension~ of the internal chamber~ is es~ential. The rabrlcation techniques described later provide thi~ accurate control.
The sample may be a fluid which is used directly as obtained from the source or may be pretreated in a variety of ways so as to modify its character. The sample will then be introduced into the device through an inlet port, which may introduce the sample into a chamber or a capillary. The sample will then transit the device passing through the capillaryties) or chamber(s), where the sample will encounter one or more reagents, which reagents are involved in a ~y3tem which produce~ a detectable signal. By having orifices which connect the pathway to the atmosphere at one or more ~ites, one can terminate the flow up to that site, 90 that the medium may be incubated ror variou3 times or movement stopped sub~ect to the initiating movement, for example, immediately prior to mea~urement.
Any liquid 3ample may be employed, where the sample will have a reasonable rate of flow due to the pumplng of the capillary action. It 19 to be understood the capillary action is the sole driving ~orce, relying on the surrace action between the surrace and the ~luid. Where the ~ample is too vlscous, it should be diluted to proyide for a 3S capillary pu~plng rate which allow3 rOr the desired manipulatians, such as mixing, and for a reasonable ~1QW time whioh wlll oontrol the time psriod rOr the aq~ay.

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The sample may be derived from any 30urce, ~uch as a physiological. ~luid, e.g., blood, saliva, ocular lens ~luid, cerebral ~pinal ~luid, pu~, swsat, exudate, urine, milk, or the like. The fluid may be sub~ected to prior treatment, ~uch as preparing serum from blood, diluting pu~, saliva, or the like, the methods o~ treatment may involve concentratLon, by filtration, distillation, dialysis, or the like;
dilution, ~iltration, inactivation of natural component~, concentration, chromatography, addition of reagent~, chemical treatment, etc.
Besides physiological fluids, other liquid samples may be employed where the component(s) of ( interest may be either liquids or solids and the solid( ) dissolved in a liquid medium. Samples o~
interest include process streams~ water, soil, plants or other vegetatLon, air, and the like.
The analytes of intere~t are widely var~ed depending upon the purpose Or the assay and the source.
Analytes may lnclude ~mall organic molecule3, such as drugs, hormones, ~teroid~, neurotransmitters, growth ~actors, commercial chemical~, degradation products, drugs of abuse, metabolites, catabolites, etc. Large organic molecules may be determined, such as nucleic ( 25 acid~, proteins, polysaccharide~, or the like.
Aggregations o~ molecules may also be of intere~t, particularly naturally-occurring aggregations such as ~iroids, viruse~, cell~, both prokaryotic and eukaryotic, including unicellular microorgani~ms, mammalian cells quch as lymphocytes, epithelial cells, nooplastic cells, and the like.
Phenomena of intere~t which may be ~easured may be indicative of physiological or non-phy~iological processes, such as blood clotting, platelet aggrega-tion, complement-medlated ly~1s, polymerization, a~glutination, etc.

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The ~ample medium may be the natural~y-occurring medium or the sample introduced into a liquid meidum whiah provide~ ror the de~ired characteristic~
nece~ary ~or the capillary pumping action and the detectable signal. For the most part, aqueous media will be employed and to that extent aqueous media will be exemplary of the media employed in the subject invention. The aqueouq media may be modified by the addition of a variety of mi~cible liquids, particularly oxygenated organic solvents, such a lower alkanols, dimethyl formamide, dimethyl sulfoxide, acetone, or the like. Usually, the solvents will be present in less than about 40 volume percent, more usually in less than about 20 volume percent. Besides other solvents, other liquid or solid additives may be included in the medium to modi~y the flow or other properties of the medium, such aq ~ugars, polyols, polymers, detergents, ~urfactants and the like, involved with changes in wetting, adherence, laminar ~low, viscosity, and the like.
In addition to the component~ mentioned above, other additives may be included for specific purposes. Bu~ers may be desirable to maintain a particular pH. Enzyme inhibitors may be included.
( 25 Other reagent3 or inter~t are antibodies, preservatives, stabilizers, ac~ivators, enæyme sub~trate~ and cofactor~, oxidant3, reductants, ~tc.
In addition, ~iltration or trapping devices may be included in the device pathway, 90 as to remove particles above a certain ~ize. The particles may include cells, viruses, latex particles, high molecular welght polymers, nucleic acids, by themselve~ or in combination with proteins, e.g., nucleosome3, magnetic particles, ligand or receptor oontalning particle~, or the like.

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- ' lo The ~ample may provide the detectable component of the detection qy~tem or such component may be added. The component(~) will vary widely depending upon the nature of the detection 3ystem. One detection method will involve the use of particle~, where particle~ provide for light scatter or a change in the rate of flow. The particles may be cells, polymeric particleq which are immiscible with the liquid ~y~tem, latex particle~, charcoal particles, metal particles, poly~accharide~ or protein particles, ceramic particles, nucleic acid particles, agglutinated particles, or the like. The choice of particle will depend upon the ease of detection, the dispersability ( or stability of ~he di3persion, inertness, participa-tion in the change in flow, and the like. Particle sizes will generally be from about 0.1-100~, more usually ~ro~ about 5-15~. Other phenomena which may be detected include changes in color, light ab~orption or transmission, ~luorescence, change in phy~ical phase, or the like.
The neat sample or ~ormulated sample will be introduced into the entry port into the receiving unit of the device. The receiving unit may be a capillary or a chamber. The recei~in~ unit may be u ed to ( 25 measure the particular sample volume or may ~imply serve to receive the aample and direct the sample to the next unlt o~ the device. The capillary units qer~e a variety of ~unctions, inoluding a measuring device rOr volume measurement, a metering pump for transferring liquid ~rom one chamber to another, rlow controller ~or controlling the rate of ~low between chambers, mixer ~or mixing reagents, and detec~ing unit for detection. For the most part, the capillaries ~ill serve as trans~er unlts, flow control unlt~ and detection units, The chamber~ and capillaries may be used to dePine dl~ferent events, e.g., areas of reaction, ar dir~erent structural entitles in certain embodiment3 Or the method.
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The capillarie~ will usually be of a ~ubstantially 3maller cro~3-section or diameter in the direction transverse to the dLrection o~ flow than the chambers. The cro~s-section or length in the direction of flow may be similar or may differ by a factor of ten or more depending on the function of the capillary and the chamber. Capillaries will usually have diameters in the range of about 0.01mm to 2mm, ueually about O.lmm to tmm. The length of the capillary, particularly the fir~t capillary in the pathway, more particularly the first capillary when it i5 joined to the entry port, will be at least about 3mm, more usually at least about 5mm, and may be 1cm or more, ( u3ually not more than about 2cm, while subsequent capillaries may be shorter or longer/ frequently at least one being longer, being as long as lOcm, usuall~
not exceeding about 5cm.
The first capillary will initially control 'he rate of flow into the chamber which will usually ~erve a~ the reaction chamber. Thus, the capillary mar aid in the oontrol of the time with which the assay medium i9 in contact with reagent contained within or bound to the wall~ of the capillary and/or reaction chamber and the progres~ of the as3ay medium through ( 25 the chamber. Other component~ which may affect the rate of flow in the chamber include baffles, walls or other impedimenta in the chamber, the geometry Or the chamber, the reagent in the chamber and the nature o~
the surface4 ln the capillary and chamber. Since in many instances the initial contactLng of the a3say msdium and the reagent could affect the results, it i~
desirable that the contact be sufficiently slow that equilLbrium can occur, as to dissolution, reaction, etc.

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thin heat conductive wall~ allow~ for rapid heat tran~fer and i30thermal conditlons, or alternatively, thlck walls can prov~de ~or adlabatic condition~.
Thu~, the small volume of ~luicl in the chambers and capillaries permitq for rapid heat exchange or efficient thermal in~ulation. In addition, the thin capillaries permit optical measurements, particularly based on transmis~lon o~ light, with optically dense ~amplQs, e.g., whole blood. There is the further opportunity for rapid efficient mixing, where b~
~onication the whole sample can be uniformly mixed.
The capillary provides the sole driving ~ource for the movement of liquid through the device.
Accordingly, careful fabrication of the capillary to exact dimensions is required. The device is normally employed in the horizontal po~ition, so that gravity does not affect the flow rate. The composition of the wall~ of the capillary are ~elected 30 a~ to provide the desired degree of wetting and ~urface tension or the wall~ are modi~ied to provide the de~ired physical propertie3. The device is employed without ancillary motive force, quch as pump~, gravity or the like.
The chamber~ al~o have a variety of ( 25 runctionq, serving a~ protection for the reagen~
mixins chamber~ rOr di~olution of reagent and~or reaction with reagent, volume mea~urement, inaubation and detection, where the detectable signal i~ other than a ~ignal as~ociated with flow, and the like. The 3 chambers wlll be primarily employed for mixing, lncubating and for holding of liquids.
Depending upon the particular ~y~tem, the length of the capillaries, their cross-sectional area, the volume~ of the variou~ chamber~, and their length and shape, may be varied widely. One con~tralnt on each of the ¢apillarle~ i3 the neceq-~ity for Sheir runctlon providing capillary pumpin~ aotlon for ~low.

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There~ore air leak~ in the qpace ~urrounding the capillary (except for designed acce~s ports) cannot be tolerated. In many in3tances, the chambers will al~o provide for capillary action while the flow rate which will be affected by the nature of the capillary ~ur~ace will be primarily determined by the capillary action of the capillaries.
In order to minimize the handling of reagent3 by the user of the device, the reagents may be supplied within the device, where by mixing with the reagents occur3 ln the device. The reagent~ may be present either diffusively or non-diffusively bound to the surface of the device, that is, adhered, absorbed, ( adsorbed or covalently-linked, so that the reagent may become dissolved in the fluid or may remain fixed to the sur~ace. Where the reagent3 are dLf~usively bound (non-covalently and weakly bound), a variety of situations can be accommodated. One ~ituation is where the liquid front dis~olves all of the reagent, so that the liquid front receives a high concentration of the reagent and most of the reaction occurs at the liquid front. A second situation would be with an excess of a reagent of limited ~olubility. In thi~ situation, the rea~ent may be present in the liquid medium at a ( 25 ~ubqtantially unlrorm concentration. A third ~ituation i9 to have a deficiency of a reagent of limited 301ubility, so that only the early portion of the fluid will ha~e a relatively constant reagent concentratlon. In many in~tances it ia essential that the reagent be pre~ent in a derined area or reaction chamber, which makes fabrication of an internal chamber followed by later addition of reagent virtually lmposaible.
While for the most part, the reagent will be present in one or more units of the device, reagents alaQ can be mechanlcally introduced by various technique~. For example, by employing a septum, a . . . . . .
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Alternatively, one could have an orifice and use an eyedropper or other mean~ for introducing liquid reagent into the unit. Usually, unless essential, these alternative technique~ will be avoided.
The reagent will vary depending upon the nature of the sample, the analyte, and the manner in which the detectable signal is genera~ed. A chemical reaction will occur due either to the formation of covalent bond~, e.g., oxidation or reduction, hydrolysis, etc., or non-covalent bonds, e.g., complex Yormation between ligand and receptor, including complex formation between nucleic acid~.
( The same or di~ferent reagent may be present in the various units, so that successive reactions can occur or a reagent continually supplied lnto the moving medium. Al~o, one could have a plurality of chambers and capillary channel~. Frequently, the rir3t unit will have a reactant. The chambers can be ~aried in size and purpose, providing the varying incubation times, varying reaction times, mixing of media ~rom difreren~ capillaries, or the like. Any number of ohambers may be employed, usually not exceeding ~ix, morë usually not exceeding about four, where the ( 25 chambers may be in serie~ or parallel. The size Or the unit, either capillary or chamber, can be particularly important, where the rea~ent is fixed, so that the re~idenoe time in oontact with the reagent will be arfected by the area of the reaBent contacted by the assay medium.
By employing variou3 filtration or trapping devioe~ (e.g., mechanical or magnetic), one can inhibit the transrer of particles rrOm a capillary channel to a chambèr or vice versa. In thi~ way, red cells can be removed from blood, various oomponents Or the sample may be removed, or by employlng divergent channel~a, one ohannel can have particles r~moved and the partlcles . .
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75~31 retaLned in the other channel where the two resul~s may be of interest.
Arbitrarily, the use of the device will be divided into two different concepts. The ~ir~t concept wiLl involve a characteri3tic other than a change in ~low rate. For the most part~ thiq will involve the ab~orption, qcatter or emi3~ion of light. A wide variety of protocol~ and reagent~ are available which provide ~or a change in the mea~ured light, as a result of absorption, scatter or emission, in relation to the amount o~ analyte in the sample.
Labelq which may be employed include enzymes, in combination with substra~es, coractors or inhibitors, ~luorescers, combinations of fluorescers and quenchers, dyes, or the like. In some inqtances a chemical reaction occurs as a result of the presence of the analyte or with the analyte, which provideq a detectable signal. By employing appropriate protocol3, the amount of absorption or emi~ion of light in the detection unit can be directly related to the amount o~
analyte in the ~ample.
Detection o~ a change in the rate of flow may -be the signal which re~ult~ from the reaction of the label or may be the result of a combination of a ( 25 plurallty of entitie~, which affect the rate Or rlow.
The change in flow rate may be as a result o~ -a~glutination, polymerization, complex formatiGn between high molacular weight compounds or aggregation3, or the like.
The mea~urement of light, e.g., ~catter, can be used to mea~ure a change in the ~ize population.
This oan be particularly useful ~or measurement o~
agglutlnatlon, clumpin~, olot ~ormation or disqolution, and the llke. A laser i9 able to diqtin~ui~h partiole gize without a change in the flow rate. Small partlcles have a low frequenc~ and a high amplitude;
lar~a partiale~ (a~glutinated particles) have a lower .
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, - ~X 75~31 ~requancy (fewer total particle~) and a higher amplitude (each particle 1~ lar~er). Thuq the change in particle ~iæe distribution may be detected by integrated noiqe employing known circuitry.
Variou~ qituation~ can be involved where the as~ay medium may have no particle~ ~entitles capable Or ~cattering) or have particle~, quch as cell~, latex bead3 and the like, where the re~ult of the reaction i~
to change the particle ~ize di~tribution, including golng from no particles to the formation of particles.
There is al~o the opportunity to begin with particle3, e.g., blood clots, and a~ a result o~ the reaction reduce the size and number of particles, e.g., dissolve ( the blood clots.
Protocols which may find u~e include those found in U.S Patent Nos. 3,817,837; 3,839,153;
3,g98,9~3; 3 7 ~35,074; 4,174,834; 4,233,402; 4,208,479;

4,235,869; 4,275,l49; 4,287,300, etc Because of the enormou~ di~ersity or protocols which are pre~ently available which can be employed in the 3ub~ect methods and de~ice~, only a rew wlll be illustrative and re~erence ~ill be made to numerous patent~ which describe di~ferent protocols.
( 25 In a rirst exemplary protoaol, a rluore~cence measurement may be made, where one ha3 a sin31e caplllary as the inlet, with the capillary coated ~ith antibody to analyte. The sample i~ dlluted with a bu~fered reagent containing a con~ugate oS analyte with rluore~cer, whereby all of the fluoreqcent reagent will become bound in the capillary in the abqence Or any analyte in the sample. The capillary i9 then introduced into the sample and an amount o~ liquid withdrawn up to an indexed polnt on the capillary, whereby the capillary ia then withdrawn from the sample and the l1quld allawed to progress into the ahamber.
When the ehamber i9 partially or completely ~ull, the ~' ~ ' . . .
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~luorescence of the chamber may then be read as indicative of the amount of analyte in the sample.
With enzymes, one could either vary the protocol or the device to prevent premature interaction between the enzyme and it~ ~ubstrate or inhibitor.
Where a simple two-unit device i5 employed, employing a capillary and chamber, one could provide ~or using a combination of enzymes, referred to as channeling, where the product o~ one enzyme is the ~ubstrate of the other enzyme. In this manner, one could have in one unit a ~econd enzyme combined with the substrate of the first enzyme, while the seeond unit having the first enzyme combined with the substrate of the second enzyme.
One could modulate the reaction by various mean~. For example, one could have antibody to analyte in the first unit and combine the ~ample with a buffered ~olution of antibody first enzyme inhibitor con~ugate. Thus, the amount Or enzyme inhibitor which would enter the second unit would be related to the amount o~ analyte in the sample. Instead of having a ~wo-unit system, one could have a three-unit 3ystem, where the ~irst unit mixes the sample with the enzyme inhibitor con~ugate a~oiding the nece~sity to combine the sample with a liquld medium. Where the sample i~
colored, ~uch a~ blood, it may be nece~sary to rilter out or trap red blood cells, to allow for development of color or ~luorescence or to find a wavelength range, where one can read the development of a particular light-absorbin3 material.
By employing a plurality of unit~, one can use a single enzyme, where the enzyme is con~ugated to the analyte. By havln~ enzyme-analyte con~ugate in a first unit, ~ollowed by antibody to anlayte in a second unit and employlng a thlrd unit containing enzyme substrat~ a~ the r~aetion chamber, the measuremQnt can be made ln the third unit.

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1;~'7~3 By employing cembinations of filters and particles one could also achieve simil~r effec~s. For example, one can employ enzyme analyte conjugates in the firqt unit which completely di~qolve in the assay medium. A second unit may then contain the particles containing antibody to the analyte. The amount o~
enzyme-analyte conjugate which bindq to the antibodie~
will be dependent upon the amount of analyte in the ~ample. By having a filter at the exit of the second unit, all of the particle~ will be trapped at the ~ilter, and only enzyme conjugate which is unbound will pas~ through the filter to the third unit. The third unit may then contain the enzyme substrate, so that reaction of the enzyme with t'ne substrate can be monitored.
For the detection o~ change in ~low rate, a wide variety of systems may be employed. or particular interest is the natural system involving clotting, which i convenient when the sample is a blood sample.
Thus, by adding one or more components o~ the clotting cascade or a component which activates the naturally-occuring components present, the clotting can provide for a change in the flow rate. Partiaularly, these reagent~ may include thromboplastin, ~actors I, ( 25 II, I~, V, VII, YIII, IX, X, XI and XII. The~e components can be added individually or in co~bination.
Particular combinations include factors of the lntrinsic pathway ~III, IX, XI and XII) or extrinsic pathway (III, VII) with the common pathway factors I, 3 II, V, X, XIII~ The clotting a~say can be used to determine a wide variety of analyte~ o~ interest. The olotting a~ay may be used for the detection of the presence of anti-clotting agents or clotting agent~.
In addition, tha clotting assay can be used ror the deteotion o~ the le~el of a particular component requlred ~or clottin~ or a componenet ln~olved in the dl~solving o~ clots~ Illustratlve analytes lnolude the variouq factor~ indicated above, war~arin, ti~sue plaqminogen activator, heparin, streptokinase, Vitamin K, anti-platelet drugs, protamine sulfate, etc.
The clotting assay can also be used to meaeure any analyte of interest by having the analyte a~sociated with a factor nece~3ary for clotting. For example, by conjugating thromboplaqtin to a compound capable of competing with the analyte for a receptor, where the thromboplastin-receptor complex is inactive, one could determine the presence of the analyte. The qample would be mixed with the receptor for the analyte 90 that the binding sites of the receptor would be oocupied by any analyte present. The thromboplastin conjugated to the analyte or mimetic analog would be the reagent in the reaction chamber. All the other components necessary for clotting would be included in the sample along with the antibodies for the analyte, where quch other components were nat naturally pre3ent in su~icient amount in the sample. The receptor sites which were not occupied by analyte would bind to the analyte conjugated to the thrombopla~tin where the resulting ~pecific binding complex would lack thromboplastin activity. The remaining uncomplexed thromboplastin con~ugate would be active and initiate ( 25 clotting. By employing appropriate standard3, one could relate the time to flow s~oppage to the amount or analyte in the ~ample. Or, one could provide that flow ~toppage dld or did not occur with an amount Or analyte above a threshold level.
Beside~ coagulation, agglutination, precipitation, or plug formation by other means, or, as approprlate, increasing vi~co~ity can be uqed as part of the deteotion scheme.
For plug formation or ~lowing of ~low by other than olotting, particles will u~ually be included in the medium whlch becom~ crosq-linked In relation to th~ amount of analyte present. This can be achived by .. . .

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1~75~31 employing receptor~ and ligand3 ~pecific ror the receptsr ~o that non-covalent binding provides for multiple linkages between particle~ with a re~ulting cros~-link ~tructure which can qerve a a plug. By us~ng such particleq a~ S. aureu , which specifically binds to i~mune complexes, red blood cell~, ~ynthetic or naturally-occurring particle~ to which ligand~, rheumatoid tactor, antibod$es, naturally-occurring receptor~, or the like, are conlugated, the cro~-linking o~ the particles can be retarded or enhanced bythe pre~ence or ab~ence of the analyte. Thus, in the case of antigen~, the antlgen may serve as a bridge between di~ferent ant~bodieq, while in the case o~
haptens, individual haptens may inhibit the cross-l~nking resulting rrom a polyhaptenic molecule.
Various illustrations can be made of thedifrerent combinations which may be employed in the flow modulation methods of the sub~ect invention. For example, the reagents could include an agaro~e bead to which i~ bound polyclonal antibodies to an antigen o~
~ntere~t or monoclonal ant~bodieq where dif~erent partioles are speciric for dif~erent epitopic 3ites of the an~igen. The 3ample need only include the detection component and any of the analyte which may be ( 25 present. The sample would mix with the antibody-con~ugated particles in the reaction unit and then flow into the exit unit. The preaence Or the analyte would re~ult ln cross-linking of the particles with large amorphou~ particle~ providing a gr~ater drag on flow ~maller particles. As the accretion o~ particle~
increased, ultimately a plu~ would ~orm and ~low would ~top. In the ca~e Or haptens, the sample could be combined with antibodies to the hapten~. The reagent could be hapten conJugated to Porglas beads. Available antibody would be capable Or cross-linkin~ the hapten-con~ugated beads so a~ to ultimately provide a plug which would inhiblt rurther ~low.
* Trade Mark . . .

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~2~5~3~l Similar techniques could be u~ed with hemag-glutination whers the particle i9 a red blood cell to which particular antigens are or have been bound. A
~ample which might contaLn cells having as part Or their surf~ce membrane the ~ame antigen would be combined with the antigen conjugated red blood cell particle~. The reagent would be antibody to the antigen. The rate of formation o~ the plug would vary depending upon whether cell3 containing the same 0 antigen were pre~ent or abqent.
A further illustration would involve polymers to which are attached polyclonal antibodies, where the polymers are ~elected so as to have only moderate ( solubility in the assay medium. Binding to antigenic 15 bridges would result in desolubilization.
The polymers could be conjugated with nucleic acid sequences complementary to pre~elected sequences.
The sequences would not be complementary to the nucleotide sequence of interest or to each other. ~he 20 !~ample could be a ly~ate o~ a viru~ or pathogenic organi~m in an appropriate aqueous medium, where the genomic polynucleotides could be ~heared. The ample would be combined with the polymeric reagents. The ~ample would then react in the reaction ohamber with a C 25 nucleotide 3equence which was a hybrid having a sequence complementary to the nucleic acid sequence oP
intere~t and a sequence complementary to the sequence bound to the polymer. Thus, the nucleic acid of lntere~t would 3erve a~ a bridse to cro~s-link the 3 polymeric molecules ~o a~ to ~e~ up a polymeric structure which would sub~tantially slow the flow in the capillary and could, i~ desired, provide a plug.
Another exempli~ication would employ dual receptors, e.g., antibody to analyte and antibody to a 35 particle, such as an antigen o~ a red blood cell SRBC).
In quantitating a multiYalent antigen, in the pre~ence o~ antigen, cros linkin~ would ocaur between the ~ .

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5~31 antigen, dual receptor and RBCs to form large complexes modulatins the ~low rate, while in the absencQ of the antigen no complexes would be formed. The assay could be carried out by combining the sample with RBCs before introducing the sample in~o the device or by providing RBCs in the ~ample receiving chamber. The reaction chamber would have the dual receptor where complex ~ormation would be initiated.
For monovalent or haptenic analytes, the assay would be modified by employing a polyhapten reagent which could be added to the sample prior to introduction of the sample into the device. The pre~ence of hapten would reduce complex formation in contrast to the result obser~ed with the multivalent antigen analyte.
Any system which re3ults in a change in ~low velocity or can be coupled to a reagent or system which affects flow veloclty may be measured. Various systems have already been indicated which result in changes in flow rate. Other systems which could be coupled to compounds of interest are light initiated catalysis of polymerization, cellular aggregation initiated by lectin cro~-linking, enzymatic reactions resulting in polymer initiation in con~unction with water-soluble monomers, e.g., hydroxyalkyl acrylates, etc.
It is evident that the sy~tem permits a wide ~ariety of variations which allows for a variety of protocol3 and reagent~ Thus, any substance Or intere3t which allows for rlow ln a capillary can be detected ln ac¢ordance with the sub~ect invention.
The ~low in the capillary channel unit can be detected by variou~ techniques which allow for detection of fluid ~`low, e~g~, flow sensors or pre~sure sensor~, or by having a detectable component in ~he assay medium, which can be detected viYually or by d1ode assay~ ~eahnlques which allow for fluid flow determination~ inolude the use o~ m~ans for measuring .--, ` ~

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triboelectricity, mean~ for detecting the rate of passage of liquid, detecting Doppler effects, or the like. Preferably, a component is used in the medium which allow~ for flow detection by detecting the passage of the component through the ~irst capillary channel exiting a receiYing chamber.
Flow can be detected by the creation of a speckle pattern re~ulting from the movement of particle in the fir~t capillary channel and the pa3~age of a coherent light source, e.gO, laser beam, or an LED, through the channe1. (See, Powers et al., supra. ) A speckle pattern results from the ( interaction of particle~ and coherent light. Flow (motion) of the particles makes the speckels move with a frequency associated with the flow rate and the light or speckle fluctuations can be detected by a photodetector. The photodetector i~ designed to detect an area not greater than about the ~ize of a ~peckle.
A plurality of photodetector element~ may be employed for detectlng different areas and averaging the signals from each area~ The ~peckle pattern can alqo be used to determine the size of the particles by analysis Or the qize of the speckles.
By employing a photodetector, the change in the light pattern as a re~ult o~ a change in the rate Or ~low can be determined by appropriate electronic mean~, such as photodiodes or phototran~ictor~, which would feed the electrical 3ignal re~ulting from the fluctuatlng light to an appropriate circuit.
Particularly easy to dls~inguish i~ a flowing liquid rrom a stationary liquid. Thua, the ~lowing ar stoppage of flow can be readily detected and the change in rate Or flow or the tlme oP pas~age through the 3S ~ir9t capillary can be determined from the be~inning of flow to the ~toppase oP Plow.

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One po3sible problem that can occur in capillary flow devices o~ the invention is depletion of blood or another ~ample from the reservoir prior to the stoppage of ~low caused by the detectable event being measured, 3uch as coagulation. When the liquid in khe re~ervoir i9 drawn down so that essentially no more ~luid is present in the reservoir, flow wlll ~top qince capillary force~ ~ill then be operating in both directions. Accordingly 9 it i~ u~eful to have a means of detecting this anomolou3 result in order to avoid a measurement of ~low stoppage caused by thi~ event being taken to represent the measurement flow stoppage.
Since the actual device containing the ( capillary channels and other chambers is typically a flat cartridge that is inserted into an instrument which makes the various electronic measurements, detection of reservoir depletion can be accompli3hed by embedding variou en~ors into the electronic device that holcls the reaction cartridge.
Since the reservoir i9 generally external to the electronic device ~o that blood or another fluid can be applied directly to the reservoir, measurement o~ depletion of fluid in the reqervoir typically takes place in the presence o~ ambient light and other ( 25 ambient c~ndition~, variation in which must be accounted for in any measurement technique~ One ~uitable measurement technique is to apply modulated light to the reservolr in a re~ion adJacent to the capillary leading to the reaction chamberq and other part~ of the apparatus. In fluids containing particleq, ~uch aq red blood cell~ in blood, lisht i9 scattered in all direction~ through the fluid even though the light i~ applled perpendicular to the re~ervoir. Some light will be scattered down the entry capillary, which will then act a~ a light guide.
However, the presence of partlcle~ in the fluld pre~ent in the caplllarr wlll a~aln re~ult in scattered light ', ' ' . .' .
: ' . , , ' - ~L2~5~

which pa~seq out through the tran~parent walls of` the lLght ~uide (capillary), where it can be measured by a photodetector. The capillary channel filled with blood can be con~idered to be a leaky waveguide for light, becau~e a difference in refracti~e index between the blood (high refractive index) bounded by a low refractive index material (capillary channel) will provide light guidance, while the presence of red blood cells will scatter the light through the walls of the capillary channel, thereby providing the leaking effect. Since light will only be scattered in the presence of red blood cells or other particles, a detector located in close proximity to the channel will ( detect the scattered light. The modulation of the applied light will isolate the detector from ambient ~nterferences. I~ the light is modulated at a de~ined frequency and detection electronics are sensitive only to that ~requency, ambient effects will be eliminated. The modulation applied to the light can be of any type, such as 3inusoidal waves or chopping, as long as the modulation can be both created and detected by electronic or mechanical means. Interferences from ambient light can further be eliminated by using in~rared light, which offers additional advantages (when blood i~ the sample) oP enhanced scattering and tran mission.
Thi~ technique for detecting depletion o~
~luid in the reservoir o~fers several advanta~es over other techniques. Detection of ~luids in capillary channels is normally accomplished by measuring changes in ab~orption or transmisslon of light passed through the channel. However, in certain instances thi~ will not be possible becau~e of the physical re3trictions on the reserYolr and its location in the caplllary device and the electronic apparatus into which the capillary device is inserted. For example, the size of a finger, if blood i9 being obtained ~rom a fin~er ~tlck, will : , . . .
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require that the reservoir be ~eparated su~ficientlY
from the electronic device to allow the finger to be placed onto the reservoir. Thiq will mean that both ~ides o~ the capillary device adjacent to the reservoir are not in contact with the electronic apparatus since at lea~t one side must be accessible ~or the finger.
With the method discu~ed here, there is no need to ha~re both ~}des o~ the capillary available for transmi~sion and detection of light. Because a scattering ef~ect is used, the detector can be present either on the same side of the capillary on which light i~ applied, on the opposite side, or in any other physical relation as long as the detector is located adjacent to the channel.
An additional u3eful control device is some means for simulating blood flow through a capillary channel in order to determine whether the electronic apparatus into which the cartridge is being inserted i~
fully operational. Numerous means of accomplishing Z this result are avallable, but one useful technique not believed to be previously u~ed in any ~imil~r manner i9 described below.
A3 described previously, one userul technique for measuring blood rlow is to detect the presence of ( 25 the speckled pattern that results rrom the interaction of particles and coherent light. Any technique that simulates blood flow when ~uch a detection system is being used will need to simulate the speckled pattern of light. Since the detec~or and the coherent light 3 source are typically located in a close spatial relationship directly opposite each other ao that insertion o~ the capillary de~ice will result in light from the coherent light source passing directly through a ohannel in the derice to the detector, simulation o~
blood rlow requires Insertlon o~ some derlce into the ele¢tronic apparatus that can modulate the light beam. While ~hlq ¢ould be accomplished using a second , ., , , , .
:, , ;i23~1 device that could, for example, produce modula~ed lLght, a useful technique is to include electronios and modulating devices directly in the capillary device so that each capillary cartridge can be used to determine the operating characteristicq of the electronic apparatus containing the coherent light ~ource and detector immediately prior to actual measurement being taken. However, thi~ requires that the ~peckled pattern generator be such that it will not then tO interfere with the actual measurement. One means o~
accomplishing these results i~ to include a liquid crystal diqplay-type apparatus at the location where meaqurement is being made. The liquid crystal material i~ selected so a~ to rotate polarized light that passes through it, ~he typical means by which liquid crystal~
operate. Polarizer filters will be present, either in the cartridge itsel~ or in the electronic apparatus into which the cartridse is inserted that will result in the pa~sage of light through the polarizing filters when the liquid cry3tal device ig turned off. However, when the liquid crystal device is activated by application o~ a voltage, light passage will be blocked.
Typically, when the liquid crystal device is ( 25 activated, it rotates tha polarization of the laser beam, thereby reducing the passage of a light and generating light amplitude fluctuations, which are detected a~ being equivalent to the mo~ing ~peckled pattern generated by pa~ing coherent light through the thin ~ilm of particle-containing fluid that would normally ~low down the capillary channel.
A low visco~lty liquid crystal material having a high re~ractive index change (thereby enabllng rapid fluatuations) i~ desirable. A typical design useq a cry3tal oqoillator and a ahain of binary counters from whioh the liquid crystal dlsplay driver si~nals are derived as well as the time base ~or the mea~urements to bo taken.

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1~75~3 In order to ~urther con~ideration 5~ the Lnvention, a number of lllu~trative devices which may be u~ed wlll now be con~idered. As already indicated, the device will have at least one capillary channel unlt, one chamber unit, an en~ry port, a vent, and a reagent bound to the ~ur~ace.
The deYice will be fabricated rrom material~
wi~h the approprlate physical proper~ies, ~uch a~
optical transmi~sion, thermal conductivity, and mechanical properti~s, and which allow for unirorm coating and stability of reagent, as well as medium compatibility, for example, blood compatibillty. Where blood i9 the medium, the material ~hould be oonfigured to as3ure good blood flow ctoppage or slow~ng once clotting is initiated. For this purpose, ~uitable plaqtics include tho~e for high surface free energies and low water sorption, including PETG, polyester (MylarR), polycarbonate (LexanR), polyvinyl chloride, polystyrene, and SAN. A particularly preferred plastic ia acrylonitrlle-butadiene-atyrene (ABS), particularly ABS supplied by ~org Warner under the trademark Cycolac. However, ~ince the~e pla~tics are hydrophobic and exhibit poor reagent coating and poor blood rlOw, the pla-~tics can be rendsred hy~rophilic by treatment ( 25 w~th argon pla~ma, uain~ a plaama etcher or corona di3char~e. Suitable conditions are 10-25 watts at 13.56MHz and one ~orr chamber prea~ure ror 5-10min.
Alternatively, a protein, e.g., albumin coating, can be used in ~ome in-~tances by pas-~ing a solution through 3 the device haYlng ~rom about 1-5~ serum albumin, allowing the solution to ~tand rOr 30min., wiping and dry~ng. Other modlfication~ may alao rind application. Plasma etchin~ and corona discharge pro~lde markedly ~uperior ~low control characteristics and reproduci~ility.

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, ~ ' ' , ' ' 1.~7~3 The device can be fabricated in a va~iety o~
way3. The receiving and reaction chamber~ can be ~ormed in the pla~tic 3heed by vacuum forming (PETG), injection ~olding (PETG, polystyrene, SAN), or hot ~tamping. Capillarie~ may be formed by etching a channel into the plastic. The device can be sealed by placing a cover slip (with appropriate vent hole~ at the inlet and vent) on the ba~e sheet, and sealing with ultra~onic welding or by solvent bonding. Of these techniques, markedly superior products are obtained by injection ~olding of the pla~tic device in piece~ so as to form a depression in at least one surface of at least one plastic piece. ABS polymers are particularly suited to injection molding and additionally provide a clear plastic which is suitable ~or numerous optical detection techniques. ABS polymers are also suitable for ultrasonic welding. It is prererred to ~orm the chamber~ from two substantially flat pla~tic pieces in which the capillarieq and other chambers are formed by producing matching depressions ln two ~urfaces o~ two difPerent shaped pla~tic piece It is preferred that on one Or the pieces ridges, known s energy directors, completely surround the depresjion in a closely ~paced relation 90 as to form a sur~ace of first contact when ( 25 ~he two pieCes are placed together. When A~S i~ used, the ridges are typically 7.5mil +0.5mil abo~e the sur~ace of the pla~tic. The rid$es are typically formed in the shape of a triangle, typically an equilateral triangle. The center o~ the ridge i~
3 typically 17.5 +0.5mils ~rom the edge of the depression that will ~orm the chamber. U~e o~ ~uch energy d~rectors with ultrasonic weldins produce~ a highly reproducible seal around the edges of the internal chambèr that ls ~ormed when the two sheets are ultra~onically welded together. Acce~s ports are typically rormed by molding or drillin3 holes into the depressed surraoe~ oP the lndivldual plastic pieces . .

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5~31 3o prior to welding. AccordLngly, the welded ridge~ form a complete seal around the lateK~al edge~ o~ the internal chambers.
Alternatively, the pattern can be dye cut in a double-sided adhe~ive tape (e.g., 3M No. 666 tape, ~asson FaYtape A) o~ appropriate thickneqs which i~
then ~andwiched between a plastic ba~e and cover ~lide.
Or, the sandwiched layer may be die cut ~rom a plastic piece o~ appropriate thickness which would be aoated with adhe~ive and san~wiched in the same manner as the tape. The adhesive could also be qilk-~creened onko the base to give a raised pattern of desired thickness.
The sheet thickness o~ the device in the ( region of the capillary channéls will generally be equal to or exceed about 2 mil to prevent compression due to the capillary action. In the embodiment involving the sandwich, each o~ the plastic layers comprising the top and bottom will be at leaqt about 10 mil thick.
While other materials may be used for fabrication, 3uch a~ glas , ~or the mo~t part the~e materials lack one or more of the de~irable characteristics Or the indicated materials and therefore have not been discuq~ed. However, there may ( 25 b@ particular qituationq where l~laqs 9 ceramic or other material may ~ind appllcation, ~uch as a glas~ window ror optical clarity, modi~ication of surfaca ten~ion, and the like.
The device will normally include a reagent within the reaction chamber. In formulating the reagent(~), it ~ay be formulated neat or with various additive~. The manner in which it is ~ormulated, introduced into the reaction chamber and maintained in the reaction chamber, mu~t provide for rapid mixing with the sample, reproducible distribution in the chamber, stability during storage, and reproducible reaction with the sample.

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In order to a~3ure the reproducibility of d1stributLon, ~arlolls technlque~ may be employed t'or introducin~ the reagen~ into ~he chamber. Where the device i9 produced a~ two parts which fit together, the reagent may be sprayed, painted, introduced into the chamber as a liquid, lyophilized or evaporated, adsorbed, covalently conjugated, or the like. The active reagent may be combined with various stabilizers, excipients, buffers or other additives involved with the reaction. Alternatively, a ~mall vial or other holder may be attached to the reaction unit, usually chamber, being stored as a liquid, where the liquid may be introduced into the reaction unit prior or concurrently with the sample entry into the reaction unit. A second receiving chamber may be employed connected to the reaction unit by a capillary channel, where ~ransfer of ~he reagent in the second receiving chamber to the reaction unit i~ initiated in relation to introduction of the ample. For example, the second receiving chamber could be rilled and ~ealed, and then unsealed when the ~ample is introduced into the sample receiving unit.
To enhance mixing, var~.ous mechanical or ultra~onic means may be employed to agitate the sample ( 25 and reagentsi where the mixing means may be internal or externaI. ~ibrator~, ultra~onic tran~ducer3, magnetic rods or other mechanical mixing means, flow disrupters, mixing baf~le~ or barrier , ~low directors, or the like, may be employed. The particular manner in which agitation i~ provided, if provided, will vary widely depending upon the degree of agitation needed, the de~ign of the device, and the like.
Various chemicals can be used to ehance dis~olution in a uniform manner. Such chemical~ may include suriactants, polyol3, sugars, emollient~, liquids, or the like. Depending upon the nature of the reagents, the reagents may be ~ormulated in a variety o~ way3 to in~ure rapid and uniform mixing.

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Other che~ical~ can also be present in the rsagent chambers. For example, i~ the de~ice i~ bein~
used to measure prothrombln time and a oontrol sampl~
containing heparin i~ being used, ~uch as de3cribed Ln an appllcation filed on even date with the pre~ent application and entLtled "Whole Blood Control Samplel', which is herein incorporated by reference, said application bein~ as igned to the ~ame assignee as the present application, a heparin antagonist can be used to eliminate the e~ectq of heparin on prothro0bin time measurement. Typical heparin antagoni t~ include protamine sulfate and polybrene.
The reagent need not be coated or bound to the surface of the device, but may be provided as a ~oluble ~ponge or gel or alternatively, absorbed onto an insoluble sponge, membrane, paper (e.g., filter paper) or gel which i5 introduced into the reaction unit. In this manner the fluid may pa~ through the ~oam structure dissolving the reagent so as to form the reaction mixture.
~ he reagent may be provlded in liquid form in microcapsule~. The liquid reagent could be released from ~he m~crocapsules by applying pressure to the walls of the reaction unit, resulting in breaking of ( 25 the microcap~ules and releasing the liquid reagent.
Al~o, a~ already indicated, the reagent need not be ll~ited to a single reaction unit. The ame or different reagent~ may be introduced into the capillary or in succeqsLve reaction units. In t~ls manner a caqcading react~on may be performed, where one i~
interested in allowing each reaction step o~ a sequence to proceed for a predetermined period berore encountering the next reagent. Multiple reaction unit~
al~o àllow ~or the removal o~ components in the sample which may interfere with the desired reaction. By havin~ receptor~ in the first unit3, one or more andogenous components may be remo~ed. ~here particles ,: ; ~,, : , ~ -.
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7~;~31 are to be removed, ~ilter~ rnay be employed at the entrance or exit to a reaction unit.
In addition to the chemical reagent, micro-particle~ may be al~o lncluded in the reaction unlt which would be entrained with the moving front, where the microparticle~ could aid in the plug-forming mechanism for flow ~toppage.
In per~ormlng the assay, a sample would be taken and treated as may be appropriate. Blood ~or example might be diluted and various reagents added, particularly where there is an interest in the determination Or a particular clotting or anti-clotting factor. In specific binding assays, various particles ( might be added which had been functionalized by the addition o~ specific binding members, such as haptens, ligands, and receptors~ particularly antibodie~. In some instances, the system may be devised where clotting will occur in the ab~ence of the analyte.
Thu~, reagents will be added which, in the absence o~
the analyteg would be degraded in the reaction chamber.
Once the various materials are mixed to ~orm the ~ample medium, the sample medium would be introduced into the receiving unit and transferred by capillary action into the next unit. Either vi~ual ( 25 evaluation of the flow rate chan~e or an slectro-mechanical evaluation may be employed. The ~nitiation o~ flow through the first capillary channel or through a ~ucce~sive capillary channel may be ~elected a~ the initiation time for mea4urement, or some point in between. As already ind~cated, various means may be employed rOr determlning the rlow velocity or time to ~low ~toppage.
For measuring a Ypeckle pattern, which is obtained with partioles, as are present in blood, an apparatus compri~ing a ~emiconductor laser and photodeQtors may be employed. By exposing a photodetector of su~iQiently small area to a speckle .

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pattern, a random signal (nol~e) i~ ob~erved. The average of the random 31gnal ob~erYed a~ a DC ~ignal is inversely proportional to the red cell den~ity, and changes in the f`luctuation contlnue~ unt~1 flow stoppage, e.g., clotting, occur~. Such apparatus may include a hou~ing ~or receivin~ and holdlng the device and means ~or controlling the temperature.
The size of the area which i~ detected by an individual photodetector may be controlled in a variety of way~. One way, a~ indicated above, 19 to use a photodetector which ha~ only a small photosen~itive area, up to about the size of the speckle spot.
Another way is to u9e an optical fiber. By controlling ( the parameters of the fiber, the area from which the ~iber receives llght may be controlled~ Instead of a fiber, lenses may be employed to limit the observed area which lenses may be ~eparate from or molded into the device.
Where other than flow stoppage i9 involved, various 3pectrophotomer3, ~luorimeter~, or the like, may be employed for detection o~ the detectable ~ignal. Depending upon the nature of the assay protocol, a single determination or multiple determination may be made, based on a fixed value or a kinetic determination.
~ arious de~ices may be devi~ed for the subject a3says. In Figure~ 1A and ~ derices are depicted involving single chambers ar.d one or two oapillary units. The~e deYice~ can be fabricated in a 3 variety of way~, for example, having two sheet3, where each of the sheeSs have been molded ~o as to define the particular units or one of the sheet~ defines the units and the other is a coYer ~heet, or having three ~heet~, where a sheet haYin~ cutouts defining the units ~
~andwiched between the other two ~heets~ where one or the other sheets provides the necessary ori~ices for the variou~ port~. Other teehniques may also be found .

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In employing device 10 o~ F1~ure lA, caplllary 12 i~ introduoed into the sample, 30 that tne inlet port 14 is completely submerged in the ~ample.
It is important to avoid any air bubble~ where the air bubbles could interfere with ~he mea~urement. The inner ~urfaae of the upper portlon o~ capillary 12 i5 coated with reagent 16, 90 that as the liquid sample tranqLt~ the capillary 12, the reagent 16 become3 dis~olved in the ~ample. When the liquid front reaches index 18, the capillary i5 remo~ed from the ~ample, defining the sample volume, and the capillary inserted ( into a second Yluid to maintain continuou3 flow.
Otherwise, the ~ample drop can maintain a reservoir outqide of the inlet port 1~. The ~ample flows through capillary 12 into chamber 20 having vent 22. A second reagent 24 is ooated onto ~hc inner ~ur~ace of reaction chamber 23, where the assay medium undergoes a second reaction.
In using thi~ device, an a~ay medium could be prepared as the ~ample involving the ~luid ~uspected of containing the analyte and a buffered mixture of - enzyme-analyte conjugate. The reagent 16 would be ( 25 antibody to the analyte, qo that the enzyme-analyte con~ugate pre~ent in the a3say medium would become bound to the antibody in an amount related to the amount of analyte in the assay medium. The assay ~edium would then enter the chamber 20, where the reagent would~be subqtrate for the enzyme. One can employ a 3ubstrate of limited solubility, 90 that the amount o~ ~ub3trate rapidly reache~ equilibrium and remains con~tant during the measurment. One can al~o have a high conoen~ration of a ~oluble ~ub~trate to maintain sub~trate concentration constant during the mea urement. Onè can then determine the rate Or i`ormatlon o~ product which will be d~pendent upon the ..

3~
amount o~ active enzyme pre~en~ ln the ohamber. Since the amount of act1ve qnzyme can be related to ~he amount o~ analyte, this rate will there~ore be proportional to the amount o~ analyte in the ~ample.
5 ay employing a ~ubstrate and enzyme whioh prodùces a colored or fluore~cent product, the rate can be monitored by the change in color or change in ~luorescence over a predetermined time period.
Xn Figure 1B, device 30 has capillary 32 which l~ divided into channel~ 34 and 36 containing reagents 38 and 40, respectively. The two channels qhare a common inlet port 42. Channel 34 contains reagent 38, referred to as the first channel and the ( ~irst reagent, which could be microparticles to which are conjugated antibodieq to a first epitope. Channel 36 and reagent 40, referred to as the second channel and the second reagent, would contain microparticles having monoclonal antibodies to a second epi~ope. In each ca~e, the amount of monoclonal antibody would be ~ubstan~ial excess Or any analyte which would be encountered. The analyte of intere~t would have a ~ingle epitope binding to the ~irst reagent and a single epitope binding to the second reagen~. The sample woùld tra~el through the channels at a ( 25 substantially constant rate, with reaction occurring with any ~ub~tance haYing the appropriate epitopc.
All o~ the components present in the as~ay medium having the appropriate epitopes would react with the particle conjugate and become bound ~o the 3 particle con~ugate~. The particle con~ugates would then exit channels 34 and 36 and enter incuba~ion chamber 44. The chamber would also provide for caplllary action, and agita~ion due to it~ accordian shape and ~anes 46 for cau~ing turbulence in the chamber 44. Thu~, a~ the a~say medium exited the channels 34 and 36, the microparticle~ would mix and cro~ link, i~ any analyte waq present which had the two epitopes on the same molecule.

. : . . , ~ , -.
, .
- : .' ' . . , . . -- . . ~ , .
, .

~L~'7~i~3 In the incubation chamber, the partlcles would have ~u~flcient time to ag~regate, 90 that upon entr~ into exlt eaplllary 48, the partioles whLch are rormed would have a signiflcant effec~ on the Plow rate in capillary 48. B~ measurLn~ the rate o~ flow or determining particle qiæe or number of particle~ in capillary 48, one could determine the pre~ence and amount of an analyte having both epitopes. The rate of ~low or other parameter could be determined by the rate at which particle~ above a certain size transited a light path, u~ing minimum light intensity fluctuations, level of qcatter, or the like.
The subject device illustrates the ( opportunity for having a plurality of capillaries to divide a sample into a plurality or portions~ where each of the portions can be treated differently. The differently treated portions may then be brought together into a sin~le chamber, where the difrerent portions may interact in accordance with the desired protocol. ~epending upon the nature of the protocol, the resulting aq~ay medium may then be tranqferred to a capillary which may provide ~or measurement or may be further tran~ferred to additional chamber~ for further modification.
( 25 In ~igures 2A and 2B are depicted a device haYing a plurality o~ chambers and a}lowing rOr Interrupted flow. The de~ice 50 ~ 9 ~abricated ~rom three ~heets, an upper ~heet 52, a lower ~heet 54, and a spacing sheet 56, which define~ the various capillary units and chamber units. The device has thre~
chamber~s, the recei~ing chamber 58, the reaction chamber 60, and the ef~luent chamber 62. Inlet port 64 receives the sample which i~ measured by filling chamber 58 and reaching the ~irst capillary 66.
ReceiYing chamber 58 is coated with flrst reagent 68, 30 that the sample undergoes a reaction in receiving chamber 58 and i9 modi~ied.

., , ............... , . ................... :.

' . : . ' ' . .
.

~ ~75~:~31 The modifled ~ample then pa~se~ through caplllary 66 and enters reaction chamber 60, whlah i~
ooated with second rea6ent 70. The second reagent, lLke the ~ir~t reaeent, i9 part of a de~eat~on ~y3tem to provide for a detectable signal. Vent 72 i9 provided to ~top the ~low and allow for incubation in reaction chamber 60. Thi~ can be particularly useful where the slow step in the development of the detection system i9 complex formation. Depending upon the nature 0 of` the protocol, the period of incubation may be specifically timed incubation or may be one which is allowed to sit for a sufficient time to ensure completion and then the determination made. Effluent chamber 62 has exit vent 74 to permit flow past intermediate vent 72 when intermed~ate vent 72 i3 closed. Upon clo~ing of intermediate vent 72, the assay medium will then ~low through capillary 76 into efrluent chamber 62. Instead of ~ealing the vent, other alternati~es, uch a~ applying pres~ure or centrifugal force, may be used to restart flow.
The device i~ comprised of a block 78 which may be conrigured to be introduQed into a instrument ~or a~say determination. As already indicated, the ~ariou~ ~heet~ will be con~tructed ~o a~ to en~ure ( ~5 ~ufficient mechanical ~tability to with~tand capillary action and pro~ide ~or the neces~ary characteri~tics ~or flow o~ the asqay medium and detection o~ the detectable ~ignal.
The sub~ect device may be employed for flow 3 stoppage, ~uch as coagula~ion, where the coagulatlon may occur in the e~fluent chamber 62. One could mea ure the rate of ~low in capillary 66 or determine the time o~ rlow stoppage, particularly where capillary 76 i~ elongated ~See Fig. 5) and a plug ~orms in capillary 76.
In thi~ device, one could provide ~or a determination of particle count, where the fir~t , .

, . . -: ', . ' . , : ' , .
~. . .. ' ~ ., , - - :

. . .: ,. ~ : ' ~:'7~31 chamber ha~ bead con~u~ated ligands and the analyte of intere~t i9 a particular antibody. The ~ample would be introduced lnto the ree~iving chamber 58, where reaotion would occur between the bead con~ugated ligand~ and any antibody present in the sample. The ~ample would then flow to the reaction chamber 60, which would contain a reagent which bind~ specifically ta an~ibody-ligand complexes, ~uch as S. aureu~ protein A or rheumatoid ractor, which binds ~pecifically to poly(antibo~y-ligand) complexes. Thu~, any bead con~ugate which beoomes bound to antibody, would be remoYed from the liquid phase o~ the a~say medium. The device 50 could then be inserted into an in~trument, which would cover vent 72, allowing for flow through capillary 76. One could then determine the number of particle~ or beads in the assay medium in the chamber 62 or capillary 76 as a measure of the amount of antibody in the ~ample.
Alternatively, one could provide for complex formation between Fab ~ragments and major histocompatibility antigens of cel}s in the receiring chamber 58. Thus, rea~ent 68 would be Fab fragments of monoclonal antibodie~ qpecific for the ma~or histocompatibility antigen. The Fab ~ragments could be ( 25 from murine or other non-human ource o~ monoclonal antibodies. The reagent 70 would then be particles to which anti-murine immunoglobulin were con~ugated. In this way, when the Fab-bound cell~ entered the reaction chamber 60, they would bind to the latex particle con~ugates ~o a9 to form extended structure~. Upon clo~ing of the vent 72 by introducing device 50 into an instrument, the medium would ~low through capillary 76, where large particles could be determined by the ~cattering of lisht, or the pattern of tran~mis~ion of light through the capillary and blockage by the cellular-particle aggregations.

..

, In Flgure 3 i~ depicted a device which l~
exemplary of the deter~ination of a plurallty of anlayte~ ln a single sampla. The device 80 ha~s a receiving chamber 82 with inlet port 84.
The sample would be introduced into the receiving chamber 82 and be pumped by capillary action through channel 86 into reaction chamber 88. In reaction chamber 88 woul~ be one or more reagents 108 which would provide part Or the detection sy~tem. From reaction chamber 88, the assay medium would then be pumped by means of oapillarie~ 90, 92 and 94 to chamber~ 96, 98 and 100, respectively. The media in chambers 96 and 98 would then be pumped by means of ( ~ide capillaries 102 and 104 to final chamber 106. In thi~ way, a variety of reaction~ could occur, where - reagents could be provided in the various side chambers ror ~urther reaction allowing for detection of a plurality o~ epitopic ~ites.
An illustrative o~ the above apparatus, one could determine from a l~sate, the qerotype of a particular pathogen. The ly~ate would be introduced through inlet port 84 into the receiving chamb~r 82 and then be pumped into the reaction chamber 88. In the reaotion chamber would be reagent 108 which would be ( 25 monoclonal antibod~-bead conjugate~ to a public epitope of the particular pathogen. One would then maa~ure the particle count in capillaries 90, 92 and 94, which would provide the ba~e line for the particle count which ~hould be pre~ent in chamber 96, 98 and 100. In 30 each of the chamber~ 96, 98 and 100, would be monoclonal antibodies to an epitope ~pecific for a particular 3erotype, where the antibodieq are con~ugated to larger beads which are distin~uishable by light ~cattering properties from the bead~ in chamber 108. Thus, i~ the signal character changeq in chamber~
96, 98 or 100, this would be indicative o~ the particular ~erotype.

. ~ .. . . - . - .

':, . ' , ' ` ' ~ ' '.`'' ' ~

~3 If one wishsd to determine If the serotype had another antigen of interest, one c~uld pro~de for antibodies to the particular antigen in chamber 106.
Chamber 106, a narrow chamber susceptLble to particle bloc~age, would have vent 110 to allow f'or flow into chamber 106. Capillarie~ 10Z and 104 would pump the assay medium ~rom chamber~ 96 and 98 into chamber 106, where the pre3ence of the particular antigen would result in cro~ linking oP the antigen. Crosq-linking o~ the antigen would result in plug formation.
Other combinations o~ labels and protocols may be employed. By dividing the assay medium into multiple pathways, the assay medium can be treated in ( multiple di~ferent ways and, if desired, rejoined in a single chamber a~ indicated above~ This can be useful in situations where one is interested in differ~nt analyte~, which may have dif~erent combinations of epitopes, or where the analyte must be treated in di~farent way~ in order to provide the detectable 2Q signal, or where one wiqhed to add different combination~ of label~ to the analyte, where one wiqhe~
to provide a check on the reqults ob~erved, or the like.
In Figure 4 is depicted a device which allows ( 25 ~or the ~lmultaneou~ determination of a sample background value and the detectable signal. The device 120 ha~ an inlet port 122 ~eparated by partition 124 wh~ch extend3 through capillary 126, chamber 128 and second capillary 130. Capillary 130 evacuates into e~fluent cha~ber 132 having vent 1340 Chamber 128 i~
div~ded into two halr chambers or semichamber~ i36 and 138. In ~emichamber 136, two reagent~ are present indicated by the slanted lines and the oro~es. The slanted lines are monoclonal antibodies speciric rOr an 3~ epitope on the analyte, where the antibodies are non-dl~rusively bound to the surface. The cro~ses indicate monoclonal antibodies con~u~ated to rluoreqcers, where :. . ', . ~ ~ , ' ,' ~
' ' ' . ' ' 5~3~L

the monocolonal antibodie~ bind to a dL~feren~ epitope o~ the analyte. The ~`luorescer con~ugate Ls re~erslbl~
bound to the surfaoe o~ the two chambers 136 and 138 ln the area near the entry ports 140 and 142 of capillary 126.
In carrying out the assay, the ~ample inLet port is sub~erged into the ~ample and the sample allowed to rise in the capillary 126. Sufficient ~ample is introduced and the two chambers 136 and 138 are ~illed.
A~ the sample tran~its the two semichambers, di~erent event~ will occur. In the sample reaction chamber any analyte will become bound both to thee `~ antibody bound to the surface and the fluorescer conjugate, so that the amount of fluorescer conjugate which remains in the sample reaction chamber 136 will be dependent upon the amount of analyte in the sample. ~y contras~, sample which traverses control reaction chamber 138 will bind to the fluorescer Z conjugate but continue through the chamber into capillary 130.
By appropriate optics, one can read the ~luore~cenae from the two capillary regions 144 and 146. The capillary region 144 will be the region for ( 25 determination o~ the amount of ~nalyte, ~hile the ~capil1ary region 146 will serve as the control. Thus9 the amount of fluore~cence ob~erved in region i46 will be the maximum amoun~ of fluorescence available ~rom the combination of ~ample and ~luore~cer con~ugate.
Any reductlon in ~luorescence in the capillary region 144 will be as a direct reqult of the presence of analyte. The two ~tream~ will then exit into e~fluent chamber 132.
A shown in Figure 5, the next embodiment 160 provide~ a ~erpentine path. The device has a hou~ing 162 which is a rectangu~ar plastic block ~haped to rit into a reading apparatu~ (not ~hown). The block is . . ..
. . .
. . . . ~ , . ........................... . .
- .

5~1 indexed at ~ite 164 for alignment to the apparatu~.
The reoeivlng ohamber 166 has a volume about one and one~half time~ the volume of the reaction chamber. The two chambers are connected by the ~irst caplllary channel 168. Inlet port 170 provideq Por introduction of the a~say ~ample by syringe, eyedropper, or other convenient means. A serpentine capillary path 172 connectq to outlet 174 of reaction chamber 176. The ~erpentine channel 172 terminates in re~ervoir chamber 178 which haq outlet port 180.
~arious oth~r oonfigurations can be employed in particular situation~. For example, one could employ a "Y"-shaped device where one arm of the Y has a ~ample receiving chamber with the inlet port sealed.
The sample receiving chamber i3 connected through a ~irst conduit to the mixing member which ~erves as the trunk of the Y. The ~ir~t conduit may be filled with a rluid which may be a buf~er solution or other diluent.
The second are o~ the Y has a ~luid chamber with a removalbe ~eal oYer a port. The rluid chamber is ~illed with a ~luld which may serve as a diluentl reagent ~ource, or the like. The ~luid chamber may be as large a~ desired 90 Shat it may provide the de~ired ratio of ~luid to s mple. The fluid chamber i~
connocted to the mixing mem~er through a ~econd conduit which is al~o rllled with the f~uid o~ the fluid chamber. The cro~-sections o~ the first and ~ec~nd conduitq are selected to provide Por the proper volume ratio o~ the ~luid and ~ample.
3 The mlxing member may be a capillary or chamber. The mixing member may be the final element of the device or may be connected to additional element~. Thu~, the Y can ~erve a~ a complete device, by providing the mixing member with an outlet port or a part of a larger device by connecting the mixing member to additional capillarie~ and~or chambers.
..... . . . .. . ... .. . . . . . . .

.
- ., - -'' ~, ' ,. , ~ . . . - .
-- .

: ': ~ . ' - , .. . .

L~4 To use the Y, the ~eé~ls ars removed from the fluid cham~er an-l ~ample ohamber, wh1le retain~n~ the outlet port aealed ~o prevent flow. T~le lnlet port may then be oontacted with the sample and the outlet port unsealed. The ~ample and ~luid ~rom the two chambers will begin to flGW and be mixed in the mixing member in the proper proportion. ~epending on the particular protocol, one can determine a number o~ dif~erent events by reading the ~low of fluid in one o~ the capillaries.
One applicatLon would be to provide fluorescent antibodie~ in the fluid chamber. Where the sample contains cells having the homologous ligand the ( mixing of the fluorescent antibodies and cells will result in large fluorescent particles as a result of the homologous antigen being present on the cells.
These large fluorescent particles could then be detected by various mean~.
Figure 6 3hows a cros~-3ectional view ~hrough a ~ection Or a hypothetical davice being prepared by ultrasonic welding from two in~ection-molded pla~tic piece~ (not nece~3arily ~ho~n in any o~ the previous ~igures), prior to ultra~onic welding. The two pla~tic piece3 202 and 204 that will be used to ~orm the internal chambers are shown properly aligned ~i.e., in regi~ter) in Figure 6A. "Registration" i9 used here in the prLnting sense, re~erring to proper alignment of the depres~ion~ pre~ent ~n the 3urfaces of the two piece~ that are used to ~orm the internal chambers and capillarle~. Proper registration can be aided by in~ection molding the two piece~ to provide pro jection3 on one piece that rit into holeq or depre3sions (other than capillary- or chamber- forming depression~) in the ~econd piece. A ~ingle convoluted depres~ion, 206 and 208, re3peotively, is formed into the 3ur~ace of each piece, but the cro~s-qectional view qhown in the ~igure cuta through the depression at ~hree qeparate :.' :, . ~ ', -,, ~-. . , .
. , . . : , , . : -' ~ . .

.

~75'~31 ~s locatlons, two Or whlch will re3ult in capillary ~paceq ~210 in Figure 6B) while the remaining location will re~ult in t~e ~ormation of a lar~er reaction chamber ~212 in Figure 6B). Energy-directing ridges 214 ean be 5 seen in the ~ur~ace oP one o~ the two plastic piece3 t204) ad~acent to the periphery of the depression.
Figure 6B hows the same cros3 sectional view a~ter ultrasonic welding. The pla3tic has melted ~electively in ~he region of the energy-directing 10 ridges ~o that the two pla~tic pieces have melted into ~ach other to form a seal around the capillary and the reaction chamber. In order to minimize the destructive effects o~ heat caused by the ultrasonic welding, C ultra30nic welding is carried out only until a seal i9 15 ~ormed and does not need to be carried out until the entire plastic surfaces have welded together. Unwelded contact sur~aces are shown by re~erence number~ 216 in Figure 6B. Use of energy ridges and short welding times also ensure ~hat ~he dimension~ of the 20 depres~ions will be unafrected by the welding event.
~elding time will be 3elected so that the melting twelding) almost but not quite reaches the edge of the depression. The extremely small crackq left between the two plates in the area or the capillaries wlll not ( 25 adversely effect capillary action.
Figure 7 shows electranic circuitry that can be utilized to simulate the passa~e o~ blood through a ; capillary ~low deYice. The circuitry includes a crystal~controlled 03cillator in which 220 represents 3o the cry tal and 222 repre~ents the oscillator. The signal from the oqcillator drives two ~requency dividers (224 and 226) that will generate the output ~lgnals for a driver 228 Or a liquid cry~tal di3play aell 230. Cell 230 iq biased by an oscillating signal 35 having a specific rate of oscillation, for example 128Hz. The cell wlll therefore rotate it3 polarization at the rate o~ 128Hz. Polarizer 231 in combination - .

. ~.

, .

'~ 7 S'~ 3 wlth cell 230 there~ore operate to alternately bloclc and pa~ light a~ a result o~ the rotating polarizat1on.
Two more divider~ ~232 and 234) ~rlve a logical AND gate (236) who~e output will go to a logic circuit low at de~ined intervals, for example, approximately every 20 ~econds. When the output goes to a logical low, the output of a logical OR gate (238) will reset the dividers, thereby stopping the proces~. Aocordingly, modulating signals ~or the liquid crystal di~play c~ll 230 are generated for the set time period, 20 ~econds in the above example.
The device is provided with a start switch ( 240. When switch 240 i~ closed, the reset signal i~
cleared, and the process is restarted.
The oscillator, dividers, logic gates, and liquid crystal display driver can be implemented in CMOS technology using standard techniques o~ electronic ~abrication. An CM05 device can be readily powered 20 through more than 10,000 cycles when powered by a coin-t~pe lithium battery.
Figure 8 shows a device ror determining when the sample present in a re3ervoir is depleted. In this ~lgure~ blood is presumed to be the 3ample. When blood ( 25 i9 applied to 3ample reservolr 242 it will start ~lowing immediately down capillary channel 244 b~
capillary actlon. A light source 246, typically an infrared light-emitting-diode (LED), is loeated adJacent to the blood reser~oir near the capillary 3 entrance~ Light ~ource 246 i~ moduIated by a ~odulator 248, typically a sinusoidal wave or square wave generator. A t~pical modulation frequency is about 8KHz~ The modulated light will be scattered by red blood cells in the blood ~ample7 and a fraction of this light will be guided by capillary channel 244 ~ormed in the plastic capillary flow device 250. Since the red blood cells ln the sample will ~urther ~catter this .,, . . . . . , . , . ,:
, - . . . . .
- . . ,, , .. : . .

-~ .
-:

5~3 gulded light, photodetector 252, typically locate~ ln close proximity to the lnlet 254 of the capillary channel, will capture ome Or the sca~tere~ l~ght. The signal output of the photodetector wlll con~qt of the ~uperpo~Ltion of ambient light and ~cattered light.
The ~cattered light component i9 3eparated ~rom the ambient light by a band-pa~s ~ilter 256 and i further ampli~ied by a~pli~er 258. Thi~ ~lgnal i~ rectir1ed by rectifier 260 and integrated by integrater 262 in order to generate a direct current voltage proportional to the scattered light. Other type~ o~ signal generator~
can be u~ed to produce a detectable signal that i~
~eperable from ambient llght and it~ pos~ible variations. Example~ include wave lengths (e.g., use of infrared light sources), light pul~e~, ~inusoidal wave genera~ion, and digital encodation. When method~
other than frequency modulation are u~ed to produce the detectable ~lgnal, the term "~ilter" a~ u~ed in thi3 ~pecification refers to any means of ~eparating the 2~ detectable signal rrom variation in ambient light.
Although the exact location Or the ambient light source and detector in relation to the Junction ~etween the blood re~ervoir and the capillary can be varied depending on the capillary size, ~trength of a ( 25 llght 30urce, detection llmit o~ the detector, ad~orbance o~ the ~ample, and the like, it i3 pre~erred that ~oth the light ~ource and the detector be relatively close to the ~unction, particularly when a highly abo~rbant ~ample such a~ blood, it i~
30 utilized. When an in~rared light 30urce i~ u3ed, it i~ -prererred to place the light source rrOm 0.5 to 2mm rrom the capillary entrance with an infr~red-~ensitive photodetector being located ~rom 1 to 4mm from the ~un~tion.
A~ the blood re~ervoir emptie~ due to the capillary ~low, the li3ht path between light ~ource 246 and photodetector 252 will be interrupted, thereby .

, :
, ~'75~31 reducing the voltage output from integrator 262. By connecting the output Or t~le intesrat~on to a comparaSor 254, a logical level indicating the presence or absence of ~qample in the re~ervoir is obtain~d.
Furthermore, by ad~usting the position of the light ~ource or the re~erence voltage of the comparator, the volume o~ sample in the reservoir at which the deciqion "no _ample" i9 made can be controlled.
An infrared light source i9 preferred becau~qe o~ it~q larger ef~iciency in converting electric current into light, a~ compared to vi~ible-light light emitting-diodes. A modulating frequency of ~everal kilohertz (preferably 3 to 20 kHz) is selected in order ( the mo~e the modulation ~requency from the low 60Hz harmonicq preqent in artificial illumination, thereby simplifying the separation o~ ambient light and signal light. The separation is enhanced even ~urther by the ~election of an in~rared light source.
Obviously, various de~igns of the individual chambers and channel~ can be provided. The designs and channel~ will be selected to provide for optimum sen~iti~ity for particular a qa~s. The volumes o~ the chamber~ will be choqen ~o a3 to accommodate an appropriate sample volume. The nature and croqs ( 25 section of the fir~t capillary~channel together with t~e size of the reaction chamber will control the residence tlme o~ the as~ay medium in the reaction chamber. In some ~ystem3 a reaction will terminate upon the sample exiting the reaction chamber, e,g., antigen-antibody~ complex rormation, pro-enzyme to enzyme, etc., where a component is bound to the ~urface Or the chamber. The reaction occurring in the react~on chamber, may result in a product which produceq a blockage in the 3econd capillarly channel or preventq a blockage rrom rorming. The re~idence time for the reaction in the reaction chamber can be care~ully controlled by controlling the dimen~ion~ o~ the .. . . . ..

: . - .
.. . .

'S~,.3 caplllary channels and reaction chamber, a~ well as temperature.
It is evident that any type o~ caplllar~
channel may be employed which provides for accommodating the appropriate volume and time period to rlow ~toppage. Variou~ de~igns may be u~ed such as ~erpentine, linear, U-shaped, pleated, or the like.
The channel cro~3-sect~on may be circular, ellipsoid, rectangular, or combinations thereof. Th0 length of the channels may be determined empirically depending upon the other parameter~ involved.
The initial or metering channel may be of constant or varying cross-section. With a constant ( cross-section, the observed Plow velocity will diminish with the path length traver~ed. Therefore, the observed ehange in velocity will have two components:
(1) an inherent reduc~ion in ~elocity related to the inorea3ing friction with increasing ~luid path length;
and (2) increasing or decrea~ing vi~cosity of the medium due to any reaction occurring.
In order to eliminate the effect of the ~luid path length, a tapered cap~llary may be employed. The taper can be calculated by determining the cross-section, e.g., helght and w~dth9 of the channel Por ( 25 each point along the channel path. The equation~ below are employed. The equation~ are ba~ed on known principlea of ~luid mechanics ~e.6., R. Byron Bird ~arren E. Stewart, Edwin N. Lightfoot, Tran~port Phenomena, John ~iley & Son~, Inc., 1960).
The flowrate, Q, meaqured by the laser 5in the first capillary channel) can be deflned by:

Q ~ VA ~ ~r4 ~ ~p 8~ z (1) where, V is the velocity in the 2nd capillary, and A i3 the area oP the l~t capillary channel, and:

. . , - , , , , . " . ' . .

, . .

5~

r ~ radiu~ o~ the 2nd caplllary chann~l ~isco~ity o~' the rlu~d z ~ dI~tance down the 2nd capillary channeL
~P ~ the pre~ure drop In the 2nd capi~lary is de~ined by:

aP ~ ~ (2) r wherein:

( Y - surface tension o~ the ~luid ~ , contact angle Or ~luid with ~ur~ace Combining (1) and (2), the rlowrate, Q, become3:

Q ~ r3~ C09 ~ (3) 4z~

Form (3) it can be aeen that the radiu~ of the 2nd : capillary channel is proportional to the distance down the channel, z:
25: ~
r ~ kz /
where k n 4Q~u _ _ :
: i: : : : Y7r c~s ~ .
~: ~30 : ~ ; :
~ : and Q* i3 the desired con~tant rlowrate in the 2nd : . capillary chann~
::: : :

: 35 .

~: ;
.' . : . : . . ~ :
., .. : .
..

5~

Uslng t~e a~ov~ equatLon3 an~ sel~cting a deqired Q~, the rollowing table indlcat~q the changes ln radlu~ at the po~ltion de~ined by z, ~or k ~ 0.034 Length ~adius Flowrate Inc Vol Vol Flow Tlme 0.090 0.206 0.13 0,127 0.62 o;osa 0;103 0.13 0.254 1.85 1015 o.ogo 0.069 0.13 0.3~2 3.70 0.092 0;056 0.13 0.515 6.11 0.099 0.056 0.16 0.671 8.91 0;106 0.056 0.18 0.846 12.06 ( 35 0.111 0;056 O.i9 1.040 15.56 1540 0;116 0.056 0;21 1.253 19.38 0.121 0.056 0.23 1.482 23.51 0~125 0;056 0.25 1;729 27;95 0.129 0.056 0.26 1.992 32.68 0.133 0;056 ~ 0.28 2.270 37;68 20~5 0.137 0.056 0.29 2.563 42.97 O;i40 0.056 0.31 2;872 48 52 0.143 0.056 0.32 3.195 54.33 0.147 0.056 0.34 3.532 60.40 0.149 0.056 0.35 3.883 66.72 . .
2590 U.152 0.056 0.36 4.248 73.28 0.155 0.~056 0~.38 ~.626 80.08 100 0.158 0.056 0.39 5.017 87.12 105 0.160 0.056 0.40 5.421 94~40 i10 0.163 0;056 0.42 6;l~38101 ;90 3: 115 0.165 oios6 0,43 6.?67iog.63 120 0;i68 0.056 ;0;44 6.709117.5~
0~170 0.056 0.45 7.16312S.75 130 0.172 0.056 0.47 7.629134.13 135 0.174 0.056 0~48 8.107142.73 ., ,, . ' , - . :' . , Length Radius Flowrate Ino Vol Vol Flow Ti~
mnl mm mm3/sec mm3 m,n3 qe¢

5 ~l0 0.177 0.056 0.~9 8.596 151.55 145 0.179 0.056 0.50 9;098 160.56 150 0.181 0.056 0.51 9.610 169.79 155 0.183 0.056 0.52 10;134 179.22 160 0.185 0.056 0.54 10.669 188.85 It i~ evident from the above table that the path may ohange from a capillary of constant radius, to one in which the radius increaqes (e.g., a funnel) or ( decreases with distance. This formula can be used to vary veloc~ty as desired as the liquid moves dawn the capillary track or ~hrough a region o~ reagent. On could even envi~ion a pul~qating flow.
In accordance with the subject invention, novel devices and methodq are provided ~or Measuring a wide variety of ~ample characteri~tics including analyte3 of intereqt. The devices provide ~or ~imple mea3urement or volumes, mixing of reagentq, incubationq, and v1qual or instrumental determination o~ the result. The detection syqtem may involve the ( 25 absorption or emi~ion o~ light, or modulation of flow, Including qlowing, ~toppage, or their rever3al. Of ~`
particular ln~erest i3~ the u~e o~ blood where clotting can be determined or reagent~ a~eeting clotting. Alqo of interest are a wide variety of analyte~, which include naturally-occurring compounds or qynthetic drugs. The devices allow for the simultaneous performance o~ controls and comparison o~ signals from ~he two media. In addition, various eombination~ of channels and chamberq may be employed, ~o that the pathway~ can diverge and converge, be broken up into a plurality of dlfrerent pathwayq or a ~ample may be divided into a plurality of pathq and treated in a :`

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5~3 s3 variety o~ way~. The de~loes can be slmple to fabrLcate and the serpentlne path readlly devi~ed by cmploying known rabrLcatlon techniques, with par~icularly advantageous device3 belng available through use o~ the preferred fabrLcatlon technlques descrlbed herein.
The ~ollowin~ exa~ple~ are o~fered by way of illuqtrat10n and not by way Or limitation.

EXPERIMENTAL

EXAMPLE 1: Detection o~ Prothrombin Time A device or cartridge analogous to the device Figure 5 is employed. Two pieces of cellulose acetate 40mil thlck are separated by ~cored Fason fa~t tape B to provide the proper design o~ channel and chambers. The reaction chamber contain~ a thromboplastin reagent where an aqueous ~olution Or the thromboplaqtin i~ lntroduced into the chamber, the water evaporated, leaving the chamber coated with ~hrombopla3tin. The thrombopla~tin reagent compo.~it~on ~5: 15mg/ml rabbi~ brain thrombopla~in extract; 1S
glycine; 0.01% thimerosoI; 0.01% streptomycin-sulfate;
O.01% Triton* X100; 0.08% pheno~ polyethylene glycol ( 25 3500; 4~ aucrose; 0.001~ polybreneT~. The mixture i9 ly~philized and reconstituted to 0,25 origlnal volume with deionized water. Three yl of the recon~tute~
liquid i~ then placed on the reagent area o~ ~h~ devi~e and then allowed to alr dry before attaching the other sheet or cover of the deYice. A cover i~ then placed oYer the chamber-~ and channels, and a 15~1 blood 3ample is lntroduced lnto the recel~lng chamber. The device i~ then inserted into a monitor which may be thermostatted at 25C or 37C, where a gallium arsenide 35~ ~emiconductor la3er o~ wa~elength 0.78~ direat~ a beam at a site between the end~ of the channel ~oining the receiving chamber and the reaction chamber. On the * Trade Mark ~: . . , . . - .
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opposite sicte ~rom the laser is a 9il~ con photodetector of a ~mall aea ~uf~icient to detact the oscillatlng qpeckl~d pattern resultLng ~rom the red blood cells ~lowlng through tne channel. A DC ~ignal i~ ob erved with large ~luctuations. The DC ~ignal i9 inver~ely proportional ~o the red cell density, and rluctuation continues until clotting occurs. The time is then rela~ed to known standard~ to determine the clotting characteri~tic of the blood. Where warfarin 1~ being admini~tered to the blood source, the time ~or clotting can be related to the effect of warfarin on the blood clotting time. In addition, ~he light absorbance in the channel can be determined to provide for a ( hematocrit, as a further characteri~tic of the blood ~ample. Because of the short path length of the light, undiluted blood can be used which provides a further convenience.

EXAMPLE 2: Detection Or Cross-linked Fibrin Dimer by Latex Aggultination Materials: "Dimertest latex" reagent~ and control serum (MABC0 Ltd). A cartridge analogou~ to that of fLg. 5 is u~ed. Two flat piece~ of polystyrene formed by in~ection moulding are welded together to ( 25 ~orm the capillary channel and reagent chamber. The r~ceiv~ng chamber (166~ is 0.467cm wide by O.O9cm deep. The fir~t capillary channel (168) i~ i.3mm wide by O.O9mm deep. The reagent chamber (176) i~ a elip~e Or maJor axi~ 12mm and minor axi 6mm and i~ 0.09mm 30 deep. The erpentine capillary path (172) i 160mm long tapering ~rom a radiu~ of O.O9mm at the outlet of the reagent chamber to 0.185mm at the outlet port ~180).
Experimental: Sample (10~l of either bu~er or posi~ive control~ wa~ mixed with antibody coated latex ~40~1); after 3' sentle ~haking 40~1 of the mixture was inJected into the cartridge containing no - ' '.: ' . ''' . ', ', '. : . ' :' . .

reagent and inserted lnto a monLtor as described ln Example 1. The signal frorn the laser de~ector waq recorded on an Omega chart recorder (model 1202) u~lng 5V ~ull scale sen~itivity and a chart speed o~
6cm/min. The movement o~ latex particles through the light ~eam produced a slightly noi~y trace (-l chart division {0.01 full scale} peak-peak). Agglutination of the latex caused by the presence o~ the analyte (cross-linked fibrin degradation products) re~ulted in a ~ignificant increase in noi~e (~3 chart divisions peak-peak).

EXAMPLE 3: Direct Blood Grouping by Red ( Blood Cell Agglutination MaterLals: Human blood samples of known groups anticoagulated with sodium citrate. Blood grouping anti~era (American Dade).
Experimental: Resuspended blood (40~1) wa~
mixed with antiserum (40~1) and 40 ~l of the mixture in~ected into empty car~ridges (as in example 2) and result~ analyzed as in Example 2. Positive agglutination was observed aq a rapidly increa~ing noise level, negative reactions ga~e a ~teady, low, noi~e level.
( ~5 EXAMPLE 4: Direct blood grouping by ~low stop Material~: Blood samples a~ in Example 3.
Cartridges a~ described in Example 2 were employed.
Berore welding the two parts of the cartridge, the 3 serpentine track or the lower part wa~ evenly coated with 5~1 blood typing anti-serum (American Dade) which had been dialysed again~t 1~ glycine (Na~) pH 7.5 containlng 0.01% Triton X-100, 2~ sucrose and 0.5%
polyethylene glycol -3500. SolYent (water) was then remo~ed by e~aporation and t'ne two parts of the cartrid~e welded together.

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~75~3 Ex~erimental: ~lood (40~1) wa~ injected into the cartridge3 after inqertion Ln a monitor (described in example 1). The time ~or flow of red blood cells past the la~er beam to stop was recorded.

Po~itive Time or ~ 175 4 B A >270 8 0 A >200 B >187 *A po~itive reaction was deflned as Time < 120s.
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Agglutination of red b}ood cells at the leading edge of the blood cau~ed clog~ing of the track and flow ~top.
All the blood samples gave the appropriate re~ction.
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~XAMPLE 5. Blood ~roupin~ by ~low rate mea~urement~
Material~: Blood samples a3 in Example 3;
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Cartridge~ ta3 de3cribed in example 2) with 3~1 American Dade blood typing ntisera applied (a descrlbed in example 4) to the reagent chamber and dried.
~ erimental: Blood (50~1~ wa~ in~ected into the cartridge~ at room temperature. The time taken for the blood to reach known distances along the narrow .

track was recorded. Flow rate~ were then calculated ~om a knowled~e of the cros~ ~e¢tion Or the ~rack as a ~unction o~ di~tance.
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.3 Positive Blood Flow Ra~e at or so9(mm~/s? _Negati~e 6 a A 0.045 B 0.025 1 A A 0.018 B 0.045 8 0 A 0.047 B 0.047 *A posltive reaction wa~ taken as flow rate ~0.030 mm3/~.

Agglutination of red blood cell~ cau~ed a significant reduction in flow rates.

EXAMPLE 6: Use of filters_to modify ~ample composition a. Red cells were quantitatively removed from whole blood by filtration through a dry ~ilter paper disc impregnated with anti human red cells. Disc were cut to ~it the ~ample application ~ite of cartridges from Beckman ParagonR electrophore~is blotter paper (about 0.57mm thick). A metal punch of diame~er 0.467cm was u~ed. After the diso~ were ~nugly inserted in the sample f cite of the track 9 1 0~1 rabbit anti-human red cells ~25 ~Cappel)` wa~ added. This i~ enough liquid to 3aturate the paper. The llquid wa~ then evaporated under ~acuum.
When blood (40~1) was applied to the di~c abou~

7~1 clear plasma emerged into ~he track be~ore flow ~topped.
3 b. Filter paper d~sc (a~ above) impregnated with sodium deoxycholate (10~1 x 10%) were dried under vacuum and placed ln the sample application 3ite. Blood (40~1) wa~ applied at 37C. A clear uniform red ~olution free of all red cell~ filtered into and rilled the track. The absorbance of the remaining hemolysate can ~ive an accurate hemoglobln concentration.

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EXAMP~E 7: Electronic Cartrid~e An electronic cartridge capable of ~imulating the ~low o~ whole blood through a capillary was prepared u~ing a 32768Hz cr~_tal-controlled oscillator to drive two 1-16th ~requency dividers that generated the input qignal~ for a driver of a liquid cry~tal display cell prepared in accordance with the electronic diagram qet ~orth in Figure 7. This cell wa~ biased by a 2048Hz signal modulated at 128Hz intervals. The cell therefore rotated it~ polarization at the rate of 128Hz.
Two more dividers drove a logical AND gate whose output wa~ to a logic low every 20 seconds. At this point, the output of a logical OR gate reset the ( dividers, ~topping the process. Accordingly, the LCD wa~
powered and modulating ~or a 20~second interval. -A ~tart switch was provided to clear the reset signal and restart the proces~. The oscillator~, dividers, logic gate~, and LCD driver were implemented in CMOS technology and powered by a coin-type lithium ba~tery. The electronic cartidge has a li~e o~ more than 10, 000 cycle3 .

EXAMPLE 8: Out-of-Blood Detector The following ~ample depletion device wa~
( 25 prepared in the manner ~hown in ~igure 8. An infrared LED wa~ embedded into the aurface of the analytical device into which a capillary ~low cartridge was to be ln~erted so that the output of it~ ht would impinge upon the blood reservoir lmm from the capillary 3o entrance. The LED is powered by an operational amplifier confi~ured as a ~quare wave generator of about 8KHz. An infrared-3enqitive photodetector wa~ located 2mm from the ~unction of the ~ample re3ervoir and the capillary channel. The signal output o~ the detector waq pa~sed to 35 a band-pa~s filter having a center at 8KHz and a bandwidth o~ 500Hz and wa~ rurther ampli~ied by an amplLfier. The amplified ignal wa~ rcctified and .

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~'~'7 integrated, thereby generating a dlrect current voltage proportianal to the ~cattered llght.
When a blood sample i3 added to the reservolr and ~Low~ by capillary action through the capillary into other portions o~ the test cartridge, the light path between the LED and the photodetector i~ interrupted when the re~ervoLr emptie~. When the Yoltage output Or the intesrator ~alls below 50-30 millivolt, the input of this ~oltase into a comparator will indicate the ab~ence of blood in the blood reservoir.

EXAMPLE 9: Fabrication Plastic cartridges were injection molded out of ( CycolacR CTB Resin (acrylanitrile-butadiene-styrene copolymer) obtained from Borg-Warner Chemicals, Inc. The design o~ the cartridge capillary channel and overall ~tructure i~ similar to that shown in Figure 5 in that it contain~ a sample reservoir, an initial short capillary, a reagent chamber and a 3econd long oapillary. However, the configuration of the actual chambers and capillarias di~er ~rom tho~e ~hown. The cartridge consisted of a 30-mil base and a 30-mil cover. Both the cover and ba~e were pla~ma etched in an LFE Model 1002 Plasma ~ystem with the following settings: argon pressure, 2 torr:
(~ 25 argoh rlOw, 1-3; forward RF powere, 100; etch time, 20 minutes. Three microliters o~ Biotrack thromboplaqtin reagent were then applied to the base of the o~al area at the ba~e of the cartridge and allowed to dry for 10 minute3 in an environment kept at 25C and 10% relative humidity. The etched co~er was then placed on the base and welded thereto u~ing a ~ranson 8400Z uItrasonic welder with the rollowin~ settings: down ~peed, 3 ~econds; hold time, 0.5 seconds; weld energy, 0.5Kjoule;
and weld time, 0.26-0.30 3ec:0nd.
Following ~abrication, the cartridges were tested with whole blood control~ (both abnormal and normal clotting times), which are de~cribed in a . .
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~o copendlng applicatlon fLled on even date with th1s appllcatlon entitled "Whole Blood Control Sample" u~lng the Biotraak Model Monitor 1000. The prothrombin timeq were recorded. In addition, the flow rate of blood in a cartridge without reagent wa~ measured.
The resultq o~ the test were subjected to ~tati~tical analy~i~. When replicates were run, the msan and coefficient of variation were 12.3 second~ and 4.9P
for the normal control and 20.0 seconds and 2.9~ ~or the abnormal control. The ~low rate o~ blood in the capillary channel four days later was con~tant at 0.06mm3/sec. These result~ are quite superior to other fabrication techniques described in this speci~ication, ( including the example using tape qet forth in Example 1, which gave C.V.s in the 10-20~ range.

All publications and patent applications mentioned in thi~ specificatlon are indicative of level o~ ~kill of those ~killed in the art to which thls invention pertains and are herein incorporated by reference to the ~ame extent as if each indi~idual patent application and publication had been indi~idually indicated to be incorporated by reference.
Although the ~oregoing invention has been ( 25 described in ~ome detail by way of illustration and example for p~rposes of clarity of understanding, it will be obvious that certain change~ and modLfications may be practiced within the ~cope Or the appended claims.
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Claims (17)

1. A method for determining an analyte in a fluid medium employing a device comprising at least one capillary unit acting as the motive force for moving the fluid medium in the device, at least one chamber unit, an inlet port, an outlet port distant from the inlet port, and a reagent contained within the device, said reagent being a member of a detection system, wherein said capillary acts as a metering pump and flow controller of the assay medium through said device to provide for a time controlled reac-tion with said reagent, said method comprising:
introducing a fluid sample through said inlet port into one of said units and allowing said fluid sample to transit from one unit to the next unit at a rate controlled by said capillary unit and react with said reagent resulting in a detectable signal produced by said detection system; and determining said signal as a measure of the pre-sence of said analyte in said sample.

2. A method according to claim 1, wherein the detection system includes particles, and the passage of particles is observed by light scatter.

3. A method according to claim 1, wherein at least one chamber unit includes a filter.

4. A method for determining an analyte in a fluid medium employing a device comprising at least two capillary units, at least two chamber units, with two chamber units separated by a capillary unit, an inlet port, an outlet port distant from the inlet port, and a reagent bound to the surface of the device in chamber unit A, said reagent being a member of a detection system, wherein said capillary controls the rate of flow of the assay medium through said device to provide for a time controlled reac-tion with said reagent, said method comprising:

introducing through said inlet port said fluid medium into a first chamber unit;
transferring the fluid medium through a first capillary unit into said chamber unit A, whereby a reaction occurs initiating the production of said detectable signal;
and detecting said signal as a measure of the pre-sence of analyte in said fluid medium.

5. A method according to claim 4, wherein said device has a third port proximal to the outlet of chamber unit A, wherein the transit of said fluid terminates at said third port to permit an incubation period, including the additional step of sealing said third port to permit continued movement of said fluid medium from said chamber unit A into the next capillary unit.

6. A device for detecting the presence of an analyte in a fluid sample, comprising:
a capillary unit capable of independently pumping a liquid as the sole motive source in said device;
a chamber unit in fluid transfer relationship with said capillary unit;
an inlet port and an exit port positioned remote from one another and included in different units;
a reagent contained within the device, which is a member of a system capable of providing a detectable signal in relationship to the presence of said analyte;
wherein the dimensions of said capillary provide for a time controlled reaction between said reagent and said analyte.

7. A device according to claim 5, comprising at least two capillaries or chambers in fluid transfer rela-tionship with said capillaries, wherein reagent is in at least one of said chambers and chambers are connected by capillaries, wherein the walls of said capillary are hydrophobic plastic treated to enhance hydrophilicity.

8. A device according to claim 7, including a third sealable port intermediate said inlet port and exit port and proximal to the juncture between a chamber unit and a capillary unit.

9. A device according to claim 6, wherein a chamber unit includes a filtration device.

10. A device for detecting the presence of an analyte in a fluid sample, comprising:
a substantially hydrophobic housing having at least a portion of the walls treated to provide hydrophili-city, said housing comprising:
a capillary unit having hydrophilic walls and capable of pumping a liquid as the sole motive source in said device a chamber unit in fluid transfer relationship with said capillary unit;
an inlet port and exit port positioned remote from one another and included in different units;
a reagent bound to the surface of the device, which is a member of a system capable of providing a detec-table signal in relation to the presence of said analyte;
wherein the dimensions of said capillary provide for a time controlled reaction between said reagent and said analyte;
said device being fabricated from two to three sheets, wherein at least one outer sheet provides orifices for communication of a unit to the atmosphere, and where three sheets are present, a middle sheet defines said chamber and capillary units.

11. A device according to claim 10, wherein said middle layer defines at least two chambers and at least two capillaries, one of said capillaries connecting first and second chambers, the other of said capillaries being ser-pertine and in fluid receiving relationship from said second chamber.

12. A device according to claim 10, wherein one of said sheets is formed with said capillaries and chambers and the other sheet is a inner sheet.

13. A method of fabricating a plastic device having an internal chamber formed therein, which comprises:
injection molding at least two plastic pieces to be formed into said device, wherein the space that is to form said chamber is defined by a depression in a surface of at least one of said plastic pieces, wherein said plastic pieces are formed from acrylonitrile-butadiene-styrene copolymers, and wherein said injection molding forms one or more ridges adjacent to the perimeter of said depression;
modifying the surface of said depression by means of plasma etching or corona discharge;
placing said pieces in proper register; and ultrasonically welding said plastic pieces for a controlled time until said ridge or ridges melt to form a physical bond between said plastic pieces that approaches but does not extend into said depression.

14. A control device capable of simulating the flow of a particle-containing fluid, said flow being measured by an analytical instrument which utilizes an insertable analysis cartridge containing an internal chamber through which said particle-containing fluid passes, which comprises:
an insertable control cartridge;
a liquid crystal cell located in said control cartridge so as to interpose between a light source and a light detector in said analytical instrument, in which flow of said particle-containing fluid is being measured by the detection of said light: and a polarizing filter in close proximity to said liquid crystal cell located in said control cartridge so as to alternately allow and block passage of light between said light source and said light detector when voltage applied to said liquid crystal cell is modulated.

15. The control device of claim 14, wherein said control cartridge further comprises a power supply and a control circuit capable of modulating voltage supplied to said liquid crystal cell.

16. A control device capable of detecting deple-tion of a particle-containing fluid from a sample reservoir in a device comprising a sample reservoir and a capillary exitting said reservoir, which comprises:
a light source located so as to impinge on said fluid in said reservoir;
a light detector located in close proximity to said capillary so as to collect light which is reflected by said particles into said capillary and thereafter further reflected by said particles so as to pass out through the walls of said capillary;
a signal generator operably attached to said light source, wherein a detectable signal is imposed on the output of said light source; and a filter operably attached to the output of said light detector, wherein said detectable signal is isolated from other light sources which may impinge upon said light detector.

17. The control device of claim 16, wherein said light source produces infrared light and said detectable signal is a periodic variation in the intensity of said light.