US20040175300A1 - Microdevice and method for detecting a characteristic of a fluid - Google Patents
Microdevice and method for detecting a characteristic of a fluid Download PDFInfo
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- US20040175300A1 US20040175300A1 US09/759,106 US75910601A US2004175300A1 US 20040175300 A1 US20040175300 A1 US 20040175300A1 US 75910601 A US75910601 A US 75910601A US 2004175300 A1 US2004175300 A1 US 2004175300A1
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- microdevice
- wall members
- probe
- fluid channels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/11—Automated chemical analysis
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/25—Chemistry: analytical and immunological testing including sample preparation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/25—Chemistry: analytical and immunological testing including sample preparation
- Y10T436/2575—Volumetric liquid transfer
Definitions
- a “microfluidic” device typically includes fluid channels having microscale dimensions.
- a fluid channel in a typical microfluidic device may have a width of less than about 1000 microns.
- a fluid containing a chemical compound may flow towards a reaction site on the microfluidic device.
- the fluid may contact another fluid containing a different substance.
- the characteristics of the resulting fluid passing downstream of the reaction site may be detected to determine if the chemical compound reacts with the substance.
- the characteristics of the fluid may correspond to, for example, the concentration of the chemical compound in the fluid stream. If the concentration of the chemical compound in the fluid passing downstream of the reaction site is lower than the concentration of the chemical compound upstream of the reaction site, then it is likely that the chemical compound reacts with the substance.
- Microfluidic analytical systems have a number of advantages over other types of analytical systems. For example, microfluidic systems are particularly well suited for analyzing or reacting samples with low volumes. In a typical microfluidic system, samples on the order of nanoliters or even picoliters can be reacted or analyzed. Because of the small volumes of fluids being handled, microfluidic analytical systems may be used to rapidly assay large numbers of samples. The assays can be performed to study the effect of numerous compounds in various biological processes. For example, test compounds that may block, reduce, or enhance the interactions between different biological molecules, such as a receptor molecule and a corresponding ligand, may be identified as potential candidate drugs.
- test compounds that may block, reduce, or enhance the interactions between different biological molecules, such as a receptor molecule and a corresponding ligand, may be identified as potential candidate drugs.
- Embodiments of the invention address this and other problems.
- Embodiments of the invention can be used to quickly detect the characteristics of fluids in a microdevice.
- Embodiments of the invention can be used for, for example, high-throughput drug candidate screening and medical diagnostics.
- One embodiment of the invention is directed to a microdevice for supporting a flowing fluid.
- the microdevice comprises: a substrate; and a pair of generally parallel, spaced wall members on the substrate, wherein at least one of the wall members includes a pair of structures defining an opening.
- Another embodiment of the invention may be directed to a microdevice comprising: a substrate; a plurality of wall members; and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members, wherein each wall member comprises an opening that is formed by opposed beveled structures of the wall member and that communicates the adjacent fluid channels.
- Another embodiment of the invention is directed to a method for detecting a characteristic of a fluid, the method comprising: (a) inserting a probe into a fluid channel in a microdevice; (b) detecting a characteristic of a first fluid flowing in the first fluid channel; (c) moving the probe from the first fluid channel through an opening in one of the walls defining the first fluid channel and to a second fluid channel adjacent to the first fluid channel; and (d) detecting a characteristic of a second fluid flowing through the second fluid channel.
- Another embodiment of the invention is directed to an analytical assembly comprising: a detection assembly comprising a plurality of detection devices; and a microdevice comprising a plurality of wall members and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members.
- Another embodiment of the invention is directed to a method for detecting a characteristic of a fluid, the method comprising: flowing a plurality of different fluids through respective fluid channels in a microdevice, each of the fluid channels in the microdevice being formed by adjacent pairs of wall members; and detecting characteristics of the plurality of different fluids substantially simultaneously using a plurality of detection devices as the different fluids flow through their respective fluid channels.
- FIG. 1 shows a top view of a microdevice according to an embodiment of the invention.
- FIG. 2 shows a side view of the microdevice shown in FIG. 1 along the line 2 - 2 .
- FIGS. 3 ( a )- 3 ( c ) show partial top views of portions of wall members with beveled ends.
- FIG. 4 shows an end cross-sectional view of the microdevice shown in FIG. 1 along the line 4 - 4 .
- FIG. 5 is a cross-sectional view of the microdevice shown in FIG. 1 along the line 5 - 5 .
- FIG. 6 is a side cross-sectional view of an analytical system shown in FIG. 7 along the line 6 - 6 .
- FIG. 7 is a top cross-sectional view of some components of an analytical assembly according to an embodiment of the invention. Boundaries forming a slot in a cover are shown by dotted lines.
- FIG. 8 is a side cross-sectional view of an analytical assembly according to an embodiment of the invention.
- FIG. 9 is a side cross-sectional view of an analytical assembly according to an embodiment of the invention.
- FIG. 10 is a top cross-sectional view showing some components of an analytical assembly according to an embodiment of the invention.
- FIG. 11 is an end cross-sectional view of an analytical assembly shown in FIG. 10 along the lines 11 - 11 . Invisible lines show boundaries of a slot in a cover.
- FIG. 12 is a schematic diagram of an analytical assembly embodiment.
- FIG. 13 is a top view of an analytical assembly according to an embodiment of the invention.
- FIG. 14 is a graph of surface potential vs. time as a probe scans fluids flowing in fluid channels in a microdevice according to an embodiment of an invention.
- Embodiments of the invention can be used to rapidly detect characteristics of a plurality of different fluids.
- the fluids may be gases or liquids.
- Exemplary liquids include biological fluids such as blood or urine, cell extracts, organic fluids, solvents, aqueous solutions, and the like.
- Exemplary gases include air samples, hydrocarbon gases, etc.
- the fluids may comprise atoms, organic or inorganic molecules such as proteins, organelles such as cells, and the like.
- the different fluids flow through a plurality of different fluid channels at a detection region of a microdevice.
- the different fluids may have distinct characteristics and may be the products of events that occur before the different fluids flow through the detection region of the microdevice.
- the different fluids may be downstream products of upstream events such as potential or actual interactions between substances. Events may include chemical or biological reactions between two substances and binding events between two substances.
- characteristics of the fluids can be detected at the detection region of the microdevice.
- the characteristics of the fluids that are detectable may be either quantitative or qualitative in nature.
- characteristics of the fluids such as emitted radiation (e.g., light), conductivity, the pH and the like of the different fluids flowing in the different fluid channels can be detected to analyze the different fluids.
- Such characteristics may correspond to the types and/or amount of substances in the fluids.
- the detected characteristics may serve as a direct or an indirect indicator of the concentration or amount of a particular substance in the fluid.
- solutions containing protons are conductive.
- the conductivity or resistance of a fluid may be an indirect indicator of the concentration of protons in the fluid.
- Interactions that can be assayed according to embodiments of the invention may be any type of interaction normally observed for biological moieties including, for example, a catalytic reaction of an enzyme, a binding event, or a translocation by a membrane protein through a lipid bilayer.
- separate fluid samples can be screened for their ability to interact with a biological moiety.
- different fluid samples containing respectively different substances can flow through separate fluid channels in a microdevice and can be delivered to separate reaction sites on the microdevice.
- Each of the reaction sites may comprise an immobilized biological moiety, and the immobilized moieties may be bound to respective surfaces of different fluid channels.
- the biological moieties may or may not interact with the different fluid samples.
- the characteristics of the different fluids may be detected, either directly or indirectly to determine if any of the fluids of the substances in the different fluids have interacted (e.g., by binding together) with the immobilized biological moiety at each reactive site.
- one or more detection devices downstream of the reactive sites may measure the concentration of the different substances in the fluids passing downstream of the reaction sites by detecting characteristics of the fluids. If the concentration of a substance in a fluid passing downstream of a reaction site is less than the concentration of the substance in a fluid upstream of the reaction site, then it is likely that the substance in the fluid is interacting (e.g., binding or reacting) with the immobilized biological moiety.
- the concentration of a substance in a fluid downstream of the reaction site is substantially equal to the concentration of the substance upstream of the reaction site, then it is likely that little or no interaction is occurring between the substance in the fluid and the immobilized biological moiety.
- upstream events may be specific conditions that are applied to different fluids in the different fluid channels to see if the fluids or substances in the fluids change as a result of the conditions.
- a plurality of different fluids may be subjected to different heating, cooling, and irradiation (e.g., with light) conditions. Characteristics in the fluids passing downstream of these events may be detected to determine if the conditions affect the fluids.
- characteristics of the different fluids in the fluid channels may be detected by using a probe.
- the probe may pass through a plurality of different fluids in respective fluid channels by passing through openings in wall members that define the fluid channels. The characteristics of the fluids in these fluid channels can be quickly detected without exposing the end of the probe to an environment outside of the flowing fluid.
- a plurality of detectors may detect characteristics of a plurality of fluids flowing through a plurality of fluid channels in a microdevice substantially simultaneously.
- a detection assembly comprising multiple detectors may be used to detect the characteristics of the fluids flowing in the fluid channels substantially simultaneously.
- the wall members defining the plurality of fluid channels may or may not have openings.
- the microdevice may include a plurality of fluid channels defined by a plurality of wall members.
- the plurality of wall members may include at least one wall member having at least one opening that communicates two adjacent fluid channels.
- An opening in the wall member may be formed by opposing beveled structures at the internal ends of portions of the wall member.
- different fluids flowing in the adjacent fluid channels may have a laminar profile and do not mix in an appreciable manner as they flow past the opening and contact each other at the opening. Intermixing between the contacting fluids is minimal, even though there is no physical barrier in the wall member at the opening.
- a slot may be formed by the aligned openings.
- a probe disposed in a fluid in a fluid channel can move laterally through the slot and from fluid channel to fluid channel. For example, the probe can contact a fluid in a fluid channel and can detect a characteristic of that fluid. The probe can then pass through an opening in a wall member defining the fluid channel to an adjacent fluid channel where a characteristic in the adjacent fluid channel may be detected.
- characteristics of the different fluids in the fluid channels can be quickly and accurately detected by the probe and subsequently analyzed. For example, in some embodiments, the characteristics of ten different fluids flowing in the different fluid channels may be accurately detected in less than one minute.
- a probe for a pH sensor may be placed in a fluid channel to detect the pH of the fluid in that channel. Then, the probe can move laterally from one fluid channel to another adjacent fluid channel through the opening in a wall member disposed between these two fluid channels. The lateral movement of the probe can take place without withdrawing the probe from the fluids. Once the probe is in contact with the fluid in the adjacent channel, the pH of the fluid in the adjacent channel can be detected. This process can be repeated as the probe moves through the slot formed by the aligned openings in the wall members.
- a probe can pass through a number of fluid channels and can detect characteristics of the fluids in the fluid channels quickly and accurately.
- the probe need not be withdrawn from the fluid flowing in a channel and then inserted into an adjacent fluid channel.
- the distance that the probe travels between adjacent fluid channels is minimized thus reducing the time needed to analyze the fluids flowing in the microdevice.
- the probe need not be aligned in a z-direction (i.e., relative to a x-y plane formed by the orientation of the microdevice) as it moves from fluid channel to fluid channel.
- the z-direction alignment step takes time and increases the chance of damaging the probe. For example, if a probe is inserted too far into a fluid channel, the probe may contact the fluid channel bottom surface potentially damaging the probe.
- the probe can be aligned in the z-direction once. To detect the characteristics of other fluid streams, the probe may move in an x- or y-direction while remaining a predetermined distance above the fluid channel bottoms. Also, by keeping the probe at a substantially constant z position, the reliability of measurements conducted by the probe can be improved in some instances. For example, the characteristics of a fluid flowing in a fluid channel may be a function of insertion depth in a fluid.
- a probe at a substantially constant z position when detecting characteristics of multiple fluids can eliminate any potential variation in any detected characteristics that may be due to different probe insertion depths.
- purging is not required between two successive detections (e.g., two successive measurements).
- different fluids to be analyzed pass through a single fluid channel. Purging fluids are needed to separate the different fluids as they flow in series through the fluid channel.
- different fluids may flow in different, parallel fluid channels at a detection region in the microdevice. The fluids in the different fluid channels may be detected in series or in parallel without using purging fluids.
- the microdevice embodiments of the invention are especially suitable for use with biosensors.
- Typical biosensors may contain biological molecules such as lipids, enzymes, or receptors. If biological molecules such as these are exposed to air, they may become inactive. Moreover, a typical biosensor may have a variable “wetting” period after a sample fluid is applied to the biosensor.
- a probe can pass between different fluid streams without exposing the probe to an external environment such as air. Accordingly, the microdevice embodiments of the invention are especially useful for containing fluids that are to be analyzed using a biosensor.
- fluid streams can contact each other yet not mix in an appreciable manner in embodiments of the invention, reactions at the interface of two flowing fluids may be analyzed.
- One or more probes may detect the characteristics of a fluid passing downstream of the interface of the two flowing fluids to study the interaction between the two fluids.
- FIG. 1 shows a microdevice 10 comprising a substrate 12 , a plurality of inner wall members 14 a - 14 e , and a plurality of outer wall members 14 o , 14 p .
- the plurality of inner wall members 14 a - 14 e is disposed between the outer wall members 14 o , 14 p .
- Both the inner wall members 14 a - 14 e and the outer wall members 14 o , 14 p are disposed on the substrate 12 .
- the inner wall members 14 a - 14 e and the outer wall members 14 o , 14 p are substantially parallel to each other.
- the wall members 14 a - 14 e , 14 o , 14 p are spaced so that each pair of adjacent wall members 14 a - 14 e , 14 o , 14 p produces a fluid channel 16 a - 16 d .
- adjacent inner wall members 14 a , 14 b produce an inner fluid channel 16 a .
- the inner wall members 14 a , 14 e and outer wall members 14 o , 14 p form outer fluid channels 16 o , 16 p .
- inner wall member 14 a and outer wall member 14 p form a fluid channel 16 p .
- FIG. 2 shows a side view of the outer wall member 14 o and the substrate 12 of the microdevice 10 .
- the outer wall member 14 o is solid along its length and does not have an opening like the inner wall members 14 a - 14 e.
- the fluid channels 16 a - d , 16 o , 16 p in the microdevice 10 shown in FIG. 1 are substantially parallel to each other.
- the fluid channels and the wall members forming those fluid channels may have any suitable configuration.
- the fluid channels in the microdevice may be fabricated so that they are perpendicular or non-linear.
- the microdevice 10 shown in FIG. 1 has six fluid channels, it is understood that in embodiments of the invention, the microdevice 10 may have any suitable number of fluid channels.
- the microdevice 10 may have more than 10, 20 or 50 fluid channels.
- Each inner wall member 14 a - 14 e can structurally discontinue at an intermediate region to form an opening 20 a - 20 e .
- FIG. 1 has one opening 20 a - 20 e per wall member 14 a - 14 e
- each wall member may have 2, 3, 4, or any suitable number of openings.
- the wall members need not have any openings in them.
- the openings 20 a - 20 e in the members 14 a - 14 e may be aligned to form a slot 140 .
- the slot 140 formed by the aligned openings 20 a - 20 e can, for example, permit a probe (not shown) to pass from one fluid channel to another fluid channel without being removed from the microdevice 10 .
- a probe (not shown) can detect a characteristic of a first fluid flowing in a first fluid channel 16 a . After detecting the characteristic, the probe may move through the opening 20 b and into a second fluid channel 16 b .
- the probe may then detect a characteristic (e.g., pH, conductivity, fluorescence, and/or temperature) in a second fluid flowing in the second fluid channel 16 b without removing the probe from the microdevice 10 .
- a characteristic e.g., pH, conductivity, fluorescence, and/or temperature
- Fluids in the other fluid channels 16 c , 16 d , 16 o may be detected in a similar manner.
- the probe need not be withdrawn from the fluids flowing in the fluid channels 16 a - 16 d , 16 o , 16 p and need not be exposed to the outside environment. By detecting the characteristics of fluids in this manner, detection occurs quickly and accurately.
- Each inner wall member 14 a - 14 e can include one or more pairs of opposing beveled structures 24 a - 24 e that form openings 20 a - 20 e in the respective wall members 14 a - 14 e .
- a fluid having a laminar profile flowing in a fluid channel formed by the wall member is more likely to retain its laminar profile at the opening formed by the beveled structures.
- the beveled structures 24 a - 24 e may have any suitable geometry. For example, two examples of beveled structures 24 a are shown in FIGS. 3 ( a ), 3 ( b ).
- a wall member 14 a includes a beveled structure 24 a .
- the beveled structure 24 a includes a pair of tapering walls 28 a .
- the tapering walls 28 a are substantially straight.
- the tapering walls 28 a converge in an inward direction to an apex 30 and may form an angle with respect to substantially parallel side surfaces 114 a of the wall member 14 a .
- the angle may be, for example, from about 1 degree to about 89 degrees. In other embodiments, the angle may be, for example, about 2 to about 20 degrees.
- FIG. 3( b ) shows another example of a beveled structure 24 a of a wall member 14 a .
- the beveled structure 24 a also has a pair of tapering walls 28 a that converge to an apex 30 .
- the beveled structure shown in FIG. 3( b ) has curved tapering walls 28 a .
- the tapering walls 28 ( a ) curve inwards towards the apex 30 .
- the beveled structure 24 a shown in FIG. 3( b ) has a generally funnel-shaped appearance when viewed from the top.
- 3( c ) is similar to the previously shown beveled structures, but includes a smooth transition between the side surfaces 114 ( a ) and the tapering walls 28 ( a ). As shown, side surfaces 114 ( a ) may be substantially parallel to each other and may then gradually curve inwardly in the region of the tapering walls 28 ( a ).
- the particular geometries of the features of the microdevice 10 may vary. Examples of features include wall member thicknesses, fluid channel heights, and fluid channel widths. Typically, the features of the microdevice 10 have at least one dimension that is less than about 1000 microns. For example, in some embodiments, the width and depth of each fluid channel may be between about 10 microns and about 500 microns. In other embodiments, the width or depth of each fluid channel may be between about 50 microns and about 200 microns. In some embodiments, the fluid channels may sometimes be referred to as “microchannels”.
- each wall member 14 a - 14 e , 14 o , 14 p may have a width “W” of less than about 1 mm (e.g., about 20 microns to about 100 microns) and a height “D” of less than about 1 mm.
- D may be from about 50 microns to about 500 microns (e.g., about 200 microns).
- Each fluid channel 16 a - 16 d , 16 o , 16 p may have a width “w” of less than about 1 mm (e.g., about 50, 100, 150, or 200 microns).
- the distance “G” of each opening 20 a formed in a wall member 14 a may be about 1 mm or less.
- G may be from about 50 microns to about 400 microns (e.g., about 200 microns).
- the wall member 14 a structurally discontinues to form an opening 20 a so that the wall member 14 a has two distinct, separated portions.
- Each portion of the wall member 14 a may have two parts. One part may have substantially parallel sidewalls and may have a length “L 1 ” or “L 2 ”. The other part may be a beveled structure that extends along the length of the wall member 14 a a distance “S”.
- the distance L 1 or L 2 is much greater than the length S.
- the distance L 1 or L 2 may be about 1 cm or more (e.g., about 1 cm to about 5 cm).
- the length S may be about 50 microns to about 750 microns.
- the dimensions of the elements of the microdevice 10 may have values that are more or less than the specifically mentioned values.
- the fluid channels 16 a - 16 d , 16 o , 16 p may have any suitable length or configuration.
- the length of each fluid channel 16 a - 16 d , 16 o , 16 p may be from about 1 to about 20 mm in length, or more.
- the length of each fluid channel 16 a - 16 d , 16 o , 16 p can be from about 2 to about 8 mm.
- the distance between the corresponding points (e.g., opposing apexes) of opposed beveled structures in a wall member may be between about 50 and about 500 microns in some embodiments.
- Any channel cross-section geometry (trapezoidal, rectangular, v-shaped, semicircular, etc.) can be employed in the microdevice 10 .
- Trapezoidal or rectangular cross-section geometries may be used in the fluid channels 16 a - 16 d , 16 o , 16 p . Such geometries may be used with standard fluorescent detection methods.
- Fluids such as liquids or gases may be supplied to the microdevice 10 in any suitable manner.
- bulk-loading dispensing devices can be used to load all fluid channels 16 a - 16 d , 16 o , 16 p of the microdevice 10 at once with the same or different fluids.
- integrated or non-integrated microcapillary dispensing devices may be used to load fluids separately into each fluid channel 16 a - 16 d , 16 o , 16 p of the microdevice 10 .
- the flow of the fluids within the fluid channels 16 a - 16 d , 16 o , 16 p can be controlled by the selective application of voltage, current, or electrical power to the substrate to induce and/or control the electrokinetic flow of the fluids.
- fluid flow may be induced mechanically through the application of, for example, differential pressure or acoustic energy to a fluid.
- fluid flow control mechanisms are used in microfluidic devices and are known in the art.
- each of the fluids flowing in the fluid channels 16 a - 16 d , 16 o , 16 p may have a laminar profile.
- the Reynolds number, Re, for the fluid streams in the fluid channels 16 a - 16 d , 16 o , 16 p may be greater than 0 to less than or equal to about 2300.
- Re is from about 100 to about 2000.
- p is the density in gm/cm 3
- ⁇ is viscosity in gm/cm ⁇ sec
- V ave is the average velocity of the fluid
- D h is the hydraulic diameter.
- adjacent fluids flowing in adjacent fluid channels may slightly intermingle (e.g., by diffusion) via the opening that communicates the adjacent fluid channels.
- the degree of intermingling between fluids in adjacent fluid channels does not typically interfere with any measurements or detections made by a probe.
- non-sample fluids such as wash fluids may be included in one or more of the fluid channels 16 a - 16 d , 16 o , 16 p .
- a wash fluid that can be used to wash a probe may flow through one or more fluid channels 16 a - 16 d , 16 o , 16 p .
- a fluid channel 16 c containing a wash solution is disposed between two fluid channels 16 b , 16 d containing sample fluids.
- a probe may be inserted into the fluid channel 16 b to detect a characteristic of a sample fluid flowing in the fluid channel 16 b .
- the probe may be, for example, positioned in fluid channel 16 b between the openings 20 b , 20 c or may be upstream or downstream of the point between the openings 20 b , 20 c .
- the probe may pass through the opening 20 c in the wall member 14 c to the fluid channel 16 c containing a wash fluid.
- the wash fluid removes any materials that may be disposed on the probe and that may impede the probe's ability to detect a characteristic in a different fluid.
- the washed probe may pass through the opening 20 d in the wall member 14 d to the other fluid channel 16 d containing the other sample fluid.
- the washed probe can then detect a characteristic of the sample fluid in the fluid channel 16 d .
- one or more of the fluid channels 16 a - 16 d , 16 o , 16 p may contain a calibration fluid that can be used to calibrate, for example, a probe.
- the probe can be calibrated while being disposed in a calibrating fluid and may move to a fluid channel with a sample fluid after the probe is calibrated.
- FIG. 6 shows an analytical assembly comprising a probe assembly 46 and a microdevice 10 .
- the microdevice 10 in FIG. 6 is similar to the previously described microdevice 10 shown in FIG. 1, except that the microdevice 10 shown in FIG. 6 includes a cover 36 .
- the cover 36 may also comprise a plurality of fluid inlets (not shown) and a plurality of fluid outlets (not shown) that provide fluids to and remove fluids from the fluid channels 16 a - 16 d , 16 o , 16 p in the microdevice 10 .
- the cover 36 is supported by the pair of outer wall members 14 o , 14 p and may include a slot 40 .
- a pair of opposed, generally parallel, boundaries may define the slot 40 in the cover 36 .
- the slot 40 in the cover 36 is aligned with and disposed over the slot 140 formed by the holes 20 a - 20 e in the inner wall members 14 a - 14 e (see FIG. 1).
- the boundaries defining the slot 40 in the cover 36 may or may not be generally aligned with apexes of the beveled structures in the wall members 14 a - 14 e .
- a probe 44 of a probe assembly 46 is inserted through the slot 40 in the cover 36 so that an end portion 47 of the probe 44 is disposed in a fluid channel 16 a and in the slot 140 in microdevice 10 .
- the probe 44 may include an intermediate portion 45 that is upright and an end portion 47 that is skewed with respect to the intermediate portion 45 .
- the end portion 47 of the probe 40 may be substantially perpendicular to the intermediate portion 45 .
- the end portion of the probe need not be perpendicular to an intermediate portion of the probe.
- the end portion of a probe may be co-linear with an intermediate portion of the probe.
- the end portion 47 of the probe 44 is directed towards the upstream direction of the fluid flowing (which flows in direction A) through the fluid channel 16 a .
- the end portion 47 of the probe 44 may receive some of the fluid flowing in the fluid channel 16 a .
- the end portion 47 may remove a portion of the fluid for sampling.
- the probe 44 associated with the probe assembly 46 may include a micro-pipe that collects some of the fluid flowing through the fluid channel 16 a . Once collected, the sample may then be transferred to a mass spectrometer, HPLC (high pressure liquid chromatography) apparatus, or a gas chromatography apparatus.
- the micro-pipe could also be used to introduce a fluid into a fluid channel.
- the introduced fluid can be added to a fluid channel without disturbing the laminar flow profile in the flowing fluid.
- the probe 44 may move in the desired direction in the slot 40 , such as in direction of arrow B (see FIG. 7). Because the end portion 47 in this example protrudes from the upright portion 45 of the probe 44 , in order to pass the end portion 47 through the slot 40 , the end portion 47 may be initially aligned with the slot 40 and may then be inserted through the slot 40 in the cover (not shown in FIG. 7). Once the end portion 47 is in the slot 140 formed by the openings 20 a - 20 e in the wall members 14 a - 14 e , it is rotated about 90° in direction of the arrow C shown in FIG.
- the boundary 40 a at slot 40 may be aligned with the apexes 30 a - 30 e of the wall members 14 a - 14 e so that the end portion 47 of the probe 40 does not contact the apexes 30 a - 30 e as the probe 44 is inserted into the slot 40 .
- FIG. 8 shows another analytical assembly embodiment of the invention.
- the microdevice 10 includes a cover 36 having slot 40 .
- a lid 50 is on the cover 36 and is spaced from the cover 36 by supports (not shown).
- the slot 40 in the cover 36 is defined by downwardly sloping planar surfaces from boundaries 40 a and 40 b that terminate in edges 58 a and 58 b , respectively.
- the lid 50 also has a slot 60 that is generally aligned with the slot 40 in the cover 36 .
- the probe 44 may pass through both the slot 60 in the lid 50 and the slot 40 in the cover 36 .
- the embodiment shown in FIG. 8 can be used when the fluids flowing through the fluid channels are gases.
- another gas such as an inert gas (e.g., a noble gas, nitrogen, etc.) flows between the lid 50 and cover 36 .
- the inert gas may flow in a direction of the arrow D and may have a higher pressure than the gases flowing through the fluid channels formed by the wall members on the substrate 12 .
- the higher pressure gas flowing between the lid 50 and the cover 36 confines gases flowing in the fluid channels between the cover 36 and the substrate 12 and prevents diffusion of the same out of the fluid channels and into the zone between the lid 50 and the cover 36 .
- the probe assembly 46 has a probe 44 with a beveled end and not a protruding end portion as in the previous examples.
- the probe assembly in the embodiment shown in FIG. 8 could also have a protruding end portion if desired.
- FIG. 9 shows another analytical assembly embodiment of the invention.
- the microdevice 10 in this embodiment has a substrate 12 , a bottom member 80 , a slide member 90 , a cover 36 , and a probe assembly 46 , and a probe 44 .
- the bottom member 80 has a passage 82 where the slide member 90 is disposed.
- the slide member 90 may slide in a direction transverse to the orientation of the fluid channels 16 a - 16 e , 16 o , 16 p (i.e., in direction of the arrow E in FIGS. 10 and 11). As shown in FIGS.
- the substances 94 disposed on the slide member 90 may be aligned with the fluid channels 16 a - 16 e , 16 o , 16 p so that the fluids flowing within the fluid channels 16 a - 16 e , 16 o , 16 p come in contact with the substances 94 .
- the slide member 90 may support substances 94 that can contact a fluid flowing through the fluid channel 16 a prior to reaching the probe 44 of the probe assembly 46 .
- the characteristic of the fluid in the fluid channel 16 a can be detected after the fluid has contacted the substances 94 on the slide member 90 .
- the substances 94 may comprise antibodies for capturing molecules contained in the fluid flowing in the fluid channel 16 a .
- the probe 44 may then contact the downstream fluid and the probe 44 can detect a characteristic of the downstream fluid.
- the concentration of the molecules in the fluid can then be determined. If the concentration of the molecules upstream of the slide member 90 is greater than the concentration of the molecules downstream of the slide member 90 , then it can be concluded that the substances 94 on the slide member 90 interact with the molecules in the fluid.
- the microdevice 10 can be used to deposit successive layers of material on a slide member 90 . This may be done by pulling the slide member 90 through the passage 82 in the microdevice 10 . The slide member 90 may be exposed to a succession of many different fluids that may deposit different materials on the slide member 90 .
- the detection methods, detection assemblies, and analytical systems used in embodiments of the invention are not limited to those described above, and may employ any suitable optical, electrical, physical, and/or chemical detection techniques. Radiation such as visible, infrared, or ultraviolet radiation from the fluids may be detected by a detection assembly being an optical detection assembly.
- the end portion of a probe may contact the fluid flowing in a fluid channel to detect a particular characteristic of the fluid, without collecting a sample of the fluid.
- the probe may be coupled to signal analyzer (such as that sold by Hewlett-Packard, for example), an oscilloscope (such as that sold by Tektronix or Hewlett-Packard), or a lock-in amplifier (such as that commercially employed by Stanford Research System or EG&G).
- the probe may comprise a physical sensor, a biological sensor, a chemical sensor, or an electrical sensor.
- physical sensors include thermocouples, pressure sensors, flow sensors, optical fibers, etc.
- biological sensors include sensors with immobilized enzymes or immunoassays.
- electrical or chemical sensors include sensors with interdigitated electrodes having optional polymer coatings, atomic force microscopes (AFMs), Ion Sensitive Field Effect Transistors (ISFETs), light addressable potentiometric sensors (LAPSs), pH meters, and scanning probe potentiometers (SPPs). These and other types of sensors are described in Manalis et al, Applied Physics Letters , Volume 76, No. 8, Feb. 21, 2000, and other references. In comparison to optical detection devices, chemical sensors and electrical sensors are desirable as they do not need to use more expensive and inconvenient fluorescent or radiochemical tagging processes.
- An atomic force microscope allows high force sensitivity mapping of biological cells and molecules such as DNA and proteins.
- the AFM can obtain stable images of individual biomolecules while operating in physiological environments.
- molecules can be imaged directly, and the dimensions of the probe can determine the spatial resolution.
- Field effect devices such as the ISFET and the LAPS can directly detect molecular and ionic charge.
- the LAPS device has been used in a microphysiometer to monitor the response of cells to chemical substances by measuring the rate of change of the pH as protons are excreted from cells during metabolism.
- LAPS devices may be commercially obtained from Molecular Devices of Sunnyvale, Calif.
- the active areas of electrical detection devices such as AFMs, ISFETs, and SPPs are small.
- the active area in such detection devices is less than about a square millimeter, or less than 100 square microns.
- the detection sensitivity and resolution is improved in comparison to detection devices with larger active areas.
- FIG. 12 shows a schematic diagram of an analytical assembly comprising a detection assembly that detects fluorescent light coming from the fluids on a microdevice.
- the microdevice 121 is positioned on a base plate 120 .
- Light from a 100 W mercury arc lamp 125 is directed though an excitation filter 124 and onto a beam splitter 123 .
- the light is then directed through a lens 122 , such as a Micro Nikkor 55 mm 1:2:8 lens and onto the fluids flowing in the fluid channels of the microdevice 110 .
- Fluorescence emission from the device returns through the lens 122 and the beam splitter 123 .
- the emission is received by a cooled CCD camera 127 , such as the Slowscan TE/CCD-10245F&SB (Princeton Instruments).
- the camera 122 is operably connected to a CPU 128 , which is, in turn, operably connected to a VCR 129 and monitor 130 .
- the analytical assembly may comprise a detection assembly comprising a plurality of detection devices and a microdevice.
- the microdevice may comprise a plurality of wall members and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members.
- the analytical assembly may be used to detect characteristics of different fluids flowing in different fluid channels substantially simultaneously.
- the wall members of the microdevice may or may not have openings that allow adjacent fluid channels to communicate with each other.
- a plurality of different biological moieties can be screened in parallel for their ability to interact with a component of a fluid sample.
- a fluid sample can be delivered to the reactive sites in fluid channels in a microdevice where each of the different biological moieties is immobilized on a different site of the microdevice. Then, characteristics of the fluids passing downstream of the reactive sites may be detected substantially in parallel with a plurality of detection devices to study the interaction of the component with the immobilized biological moieties at each reactive site.
- a slide member 90 may comprise a number of detection devices such as sensors 194 and may form a detection assembly.
- the sensors 194 on the slide member 90 may contact the fluids flowing in the fluid channels 16 a - 16 e , 16 o , 16 p and may subsequently detect characteristics of the fluids.
- the sensors 194 may be, for example, conductivity sensors, biosensors, temperature sensors, etc.
- a probe assembly with an elongated probe, and a cover with a slot for the elongated probe are not needed.
- probe assemblies like the probe assembly 46 shown in FIG. 6 can be used.
- the probe assembly may comprise two or more elongated probes 44 . These probes may be spaced so that they can be inserted into plural fluid channels simultaneously to detect characteristics of the fluids flowing in these fluid channels substantially simultaneously.
- the number of probes in the detection assembly may be equal to or less than the number of fluid channels in the microdevice. For example, if a microdevice has six fluid channels, a probe assembly with six probes that are insertable within the six fluid channels can be used to substantially simultaneously detect characteristics of the six fluids flowing in the six fluid channels.
- a plurality of optical detectors may be positioned to receive optical signals coming from a plurality of fluids flowing in their respective fluid channels on a microdevice.
- the plurality of optical detectors may comprise a charge coupled device (CCD) array or a photodiode array. These arrays may be positioned to receive optical signals coming from the fluids flowing in the fluid channels.
- CCD charge coupled device
- radiolabels or fluorescent tags on molecules in fluids flowing in the fluid channels in a microdevice may provide such optical signals.
- the microdevices according to embodiments of the invention may be made according to any suitable process.
- portions of a body of material may be removed to form a plurality of wall members.
- the wall members may be integrally formed with the substrate.
- suitable material removal processes include bulk micromachining, sacrificial micromachining, focused ion-beam milling, electrostatic discharge machining, ultrasonic drilling, laser ablation, mechanical milling and thermal molding techniques.
- Conventional photolithographic and etching processes may be used to etch a body to form a plurality of wall members and fluid channels in the body.
- Etching processes such as reactive ion etching (RIE) or deep reactive ion etching (DRIE), or wet etching may be used to etch an appropriate body of material.
- the wall members and the underlying substrate may be formed by molding.
- wall members may be formed on a substrate.
- wall members may be formed on or bonded to a body to form a plurality of fluid channels.
- wall members may be formed by electroplating (e.g., high aspect ratio plating).
- the surfaces defining the fluid channels may be coated with a material.
- the material coated on the walls or bottom surfaces defining the channels may be an adhesion layer, coupling agents, or substances that may potentially interact with fluids flowing through the fluid channels.
- any suitable material may be used as to form the substrate and the wall members in the microdevice.
- the materials used may be organic or inorganic, and may be transparent, translucent, or non-transparent. Materials that can be micromachined or microfabricated are preferred. Suitable micromachinable materials include silicon, glass, plastic and the like. Other suitable materials, and processes for forming a plurality of fluid channels in a microdevice may be found in U.S. patent application Ser. No. 09/115,397, which is assigned to the same assignee as the present application, and International Application No. PCT/US99/15968. Both of these applications are herein incorporated by reference in their entirety for all purposes.
- a microdevice having ten fluid channels was fabricated by forming nine wall members in a silicon substrate.
- the wall members were formed in a silicon substrate using a deep reactive ion etch.
- Each of the wall members had an opening and the openings in the wall members were aligned to form a slot that passed across the nine wall members.
- the height of the wall members and the corresponding channel depth was about 200 microns.
- the width of each of the fluid channels was 110 microns, and the channel pitch was about 150 microns.
- the pH values of the different fluids flowing in the ten fluid channels were measured using a scanning probe potentiometer (SPP).
- SPP scanning probe potentiometer
- the SPP had a probe was insertable into a fluid channel and had a sensitivity of less than 0.01 pH units and a spatial resolution of 10 microns.
- the pH of the ten fluids flowing in the ten fluid channels was profiled by measuring the pH in a fluid channel proximate one side of the microdevice. After the pH values in this fluid channel are measured, the probe moves through the slot to the next adjacent fluid channel without removing the pH sensitive area of the probe from the flowing fluids. The pH value of the adjacent fluid channel was then measured. The pH values of the fluids in the remaining eight fluid channels were measured in a similar manner. The travel time between the fluid channels was about 1 second. The measurement time was about 5 seconds per channel.
- a plot of sensor potential versus time during the scanning process is shown in FIG. 14.
- the relative potential difference between each fluid channel correlates closely to the actual pH values of the fluids in the channels (listed above the plot), except for the first and last edge channels.
- Each of the plateaus in the plot corresponds to a pH measurement of a fluid in a fluid channel.
- the time used to measure the pH values of the ten fluids in the ten fluid channels was less than one minute.
Abstract
Description
- This application is a continuation-in-part of U.S. patent application Ser. No. 09/353,554, filed Jul. 14, 1999, which is a continuation-in-part of U.S. patent application Ser. No. 09/115,397, filed Jul. 14, 1998. This application also claims the benefit of the filing date of U.S. provisional patent application No. 60/175,997, filed Jan. 12, 2000. All of the above U.S. provisional and non-provisional applications are assigned to the same assignee and are all herein incorporated by reference in its entirety for all purposes.
- Work is now underway to develop microfluidic devices for analyzing chemical or biological fluids. A “microfluidic” device typically includes fluid channels having microscale dimensions. For example, a fluid channel in a typical microfluidic device may have a width of less than about 1000 microns.
- In a typical application for a microfluidic device, a fluid containing a chemical compound may flow towards a reaction site on the microfluidic device. At the reaction site, the fluid may contact another fluid containing a different substance. The characteristics of the resulting fluid passing downstream of the reaction site may be detected to determine if the chemical compound reacts with the substance. The characteristics of the fluid may correspond to, for example, the concentration of the chemical compound in the fluid stream. If the concentration of the chemical compound in the fluid passing downstream of the reaction site is lower than the concentration of the chemical compound upstream of the reaction site, then it is likely that the chemical compound reacts with the substance.
- Microfluidic analytical systems have a number of advantages over other types of analytical systems. For example, microfluidic systems are particularly well suited for analyzing or reacting samples with low volumes. In a typical microfluidic system, samples on the order of nanoliters or even picoliters can be reacted or analyzed. Because of the small volumes of fluids being handled, microfluidic analytical systems may be used to rapidly assay large numbers of samples. The assays can be performed to study the effect of numerous compounds in various biological processes. For example, test compounds that may block, reduce, or enhance the interactions between different biological molecules, such as a receptor molecule and a corresponding ligand, may be identified as potential candidate drugs.
- In recent years, the number of test compounds produced by modern combinatorial chemistry techniques has dramatically increased. While conventional microfluidic systems can be used to test the increasing number of compounds, the throughput of such systems could be improved. There is a continuing need to screen large numbers of samples quickly and accurately.
- Embodiments of the invention address this and other problems.
- Embodiments of the invention can be used to quickly detect the characteristics of fluids in a microdevice. Embodiments of the invention can be used for, for example, high-throughput drug candidate screening and medical diagnostics.
- One embodiment of the invention is directed to a microdevice for supporting a flowing fluid. The microdevice comprises: a substrate; and a pair of generally parallel, spaced wall members on the substrate, wherein at least one of the wall members includes a pair of structures defining an opening.
- Another embodiment of the invention may be directed to a microdevice comprising: a substrate; a plurality of wall members; and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members, wherein each wall member comprises an opening that is formed by opposed beveled structures of the wall member and that communicates the adjacent fluid channels.
- Another embodiment of the invention is directed to a method for detecting a characteristic of a fluid, the method comprising: (a) inserting a probe into a fluid channel in a microdevice; (b) detecting a characteristic of a first fluid flowing in the first fluid channel; (c) moving the probe from the first fluid channel through an opening in one of the walls defining the first fluid channel and to a second fluid channel adjacent to the first fluid channel; and (d) detecting a characteristic of a second fluid flowing through the second fluid channel.
- Another embodiment of the invention is directed to an analytical assembly comprising: a detection assembly comprising a plurality of detection devices; and a microdevice comprising a plurality of wall members and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members.
- Another embodiment of the invention is directed to a method for detecting a characteristic of a fluid, the method comprising: flowing a plurality of different fluids through respective fluid channels in a microdevice, each of the fluid channels in the microdevice being formed by adjacent pairs of wall members; and detecting characteristics of the plurality of different fluids substantially simultaneously using a plurality of detection devices as the different fluids flow through their respective fluid channels.
- These and other embodiments of the invention are described in further detail with reference to the Figures and the Detailed Description.
- FIG. 1 shows a top view of a microdevice according to an embodiment of the invention.
- FIG. 2 shows a side view of the microdevice shown in FIG. 1 along the line2-2.
- FIGS.3(a)-3(c) show partial top views of portions of wall members with beveled ends.
- FIG. 4 shows an end cross-sectional view of the microdevice shown in FIG. 1 along the line4-4.
- FIG. 5 is a cross-sectional view of the microdevice shown in FIG. 1 along the line5-5.
- FIG. 6 is a side cross-sectional view of an analytical system shown in FIG. 7 along the line6-6.
- FIG. 7 is a top cross-sectional view of some components of an analytical assembly according to an embodiment of the invention. Boundaries forming a slot in a cover are shown by dotted lines.
- FIG. 8 is a side cross-sectional view of an analytical assembly according to an embodiment of the invention.
- FIG. 9 is a side cross-sectional view of an analytical assembly according to an embodiment of the invention.
- FIG. 10 is a top cross-sectional view showing some components of an analytical assembly according to an embodiment of the invention.
- FIG. 11 is an end cross-sectional view of an analytical assembly shown in FIG. 10 along the lines11-11. Invisible lines show boundaries of a slot in a cover.
- FIG. 12 is a schematic diagram of an analytical assembly embodiment.
- FIG. 13 is a top view of an analytical assembly according to an embodiment of the invention.
- FIG. 14 is a graph of surface potential vs. time as a probe scans fluids flowing in fluid channels in a microdevice according to an embodiment of an invention.
- Embodiments of the invention can be used to rapidly detect characteristics of a plurality of different fluids. The fluids may be gases or liquids. Exemplary liquids include biological fluids such as blood or urine, cell extracts, organic fluids, solvents, aqueous solutions, and the like. Exemplary gases include air samples, hydrocarbon gases, etc. Regardless of the form of the fluids, the fluids may comprise atoms, organic or inorganic molecules such as proteins, organelles such as cells, and the like.
- The different fluids flow through a plurality of different fluid channels at a detection region of a microdevice. The different fluids may have distinct characteristics and may be the products of events that occur before the different fluids flow through the detection region of the microdevice. For example, the different fluids may be downstream products of upstream events such as potential or actual interactions between substances. Events may include chemical or biological reactions between two substances and binding events between two substances.
- Downstream of the events, characteristics of the fluids can be detected at the detection region of the microdevice. The characteristics of the fluids that are detectable may be either quantitative or qualitative in nature. In some embodiments, characteristics of the fluids such as emitted radiation (e.g., light), conductivity, the pH and the like of the different fluids flowing in the different fluid channels can be detected to analyze the different fluids. Such characteristics may correspond to the types and/or amount of substances in the fluids. In some embodiments, the detected characteristics may serve as a direct or an indirect indicator of the concentration or amount of a particular substance in the fluid. For example, solutions containing protons are conductive. The conductivity or resistance of a fluid may be an indirect indicator of the concentration of protons in the fluid.
- Interactions that can be assayed according to embodiments of the invention may be any type of interaction normally observed for biological moieties including, for example, a catalytic reaction of an enzyme, a binding event, or a translocation by a membrane protein through a lipid bilayer. In embodiments of the invention, separate fluid samples can be screened for their ability to interact with a biological moiety. For example, different fluid samples containing respectively different substances can flow through separate fluid channels in a microdevice and can be delivered to separate reaction sites on the microdevice. Each of the reaction sites may comprise an immobilized biological moiety, and the immobilized moieties may be bound to respective surfaces of different fluid channels. At the reaction sites, the biological moieties may or may not interact with the different fluid samples. Downstream of the reaction sites, the characteristics of the different fluids may be detected, either directly or indirectly to determine if any of the fluids of the substances in the different fluids have interacted (e.g., by binding together) with the immobilized biological moiety at each reactive site. For example, one or more detection devices downstream of the reactive sites may measure the concentration of the different substances in the fluids passing downstream of the reaction sites by detecting characteristics of the fluids. If the concentration of a substance in a fluid passing downstream of a reaction site is less than the concentration of the substance in a fluid upstream of the reaction site, then it is likely that the substance in the fluid is interacting (e.g., binding or reacting) with the immobilized biological moiety. On the other hand, if the concentration of a substance in a fluid downstream of the reaction site is substantially equal to the concentration of the substance upstream of the reaction site, then it is likely that little or no interaction is occurring between the substance in the fluid and the immobilized biological moiety.
- In another example, upstream events may be specific conditions that are applied to different fluids in the different fluid channels to see if the fluids or substances in the fluids change as a result of the conditions. For instance, a plurality of different fluids may be subjected to different heating, cooling, and irradiation (e.g., with light) conditions. Characteristics in the fluids passing downstream of these events may be detected to determine if the conditions affect the fluids.
- In some embodiments of the invention, characteristics of the different fluids in the fluid channels may be detected by using a probe. The probe may pass through a plurality of different fluids in respective fluid channels by passing through openings in wall members that define the fluid channels. The characteristics of the fluids in these fluid channels can be quickly detected without exposing the end of the probe to an environment outside of the flowing fluid.
- In other embodiments of the invention, a plurality of detectors may detect characteristics of a plurality of fluids flowing through a plurality of fluid channels in a microdevice substantially simultaneously. A detection assembly comprising multiple detectors may be used to detect the characteristics of the fluids flowing in the fluid channels substantially simultaneously. In these embodiments, the wall members defining the plurality of fluid channels may or may not have openings.
- These and other embodiments are described in further detail below.
- I. Embodiments Using Microdevices
- One embodiment of the invention is directed to a microdevice. The microdevice may include a plurality of fluid channels defined by a plurality of wall members. The plurality of wall members may include at least one wall member having at least one opening that communicates two adjacent fluid channels. An opening in the wall member may be formed by opposing beveled structures at the internal ends of portions of the wall member. In embodiments of the invention, different fluids flowing in the adjacent fluid channels may have a laminar profile and do not mix in an appreciable manner as they flow past the opening and contact each other at the opening. Intermixing between the contacting fluids is minimal, even though there is no physical barrier in the wall member at the opening.
- When openings in the respective wall members in the microdevice are aligned, a slot may be formed by the aligned openings. A probe disposed in a fluid in a fluid channel can move laterally through the slot and from fluid channel to fluid channel. For example, the probe can contact a fluid in a fluid channel and can detect a characteristic of that fluid. The probe can then pass through an opening in a wall member defining the fluid channel to an adjacent fluid channel where a characteristic in the adjacent fluid channel may be detected. By analyzing different fluids in this manner, characteristics of the different fluids in the fluid channels can be quickly and accurately detected by the probe and subsequently analyzed. For example, in some embodiments, the characteristics of ten different fluids flowing in the different fluid channels may be accurately detected in less than one minute.
- Illustratively, a probe for a pH sensor may be placed in a fluid channel to detect the pH of the fluid in that channel. Then, the probe can move laterally from one fluid channel to another adjacent fluid channel through the opening in a wall member disposed between these two fluid channels. The lateral movement of the probe can take place without withdrawing the probe from the fluids. Once the probe is in contact with the fluid in the adjacent channel, the pH of the fluid in the adjacent channel can be detected. This process can be repeated as the probe moves through the slot formed by the aligned openings in the wall members.
- Embodiments of the invention provide a number of advantages. For example, in embodiments of the invention, a probe can pass through a number of fluid channels and can detect characteristics of the fluids in the fluid channels quickly and accurately. The probe need not be withdrawn from the fluid flowing in a channel and then inserted into an adjacent fluid channel. The distance that the probe travels between adjacent fluid channels is minimized thus reducing the time needed to analyze the fluids flowing in the microdevice. Moreover, since a probe need not be withdrawn from a fluid, the probe need not be aligned in a z-direction (i.e., relative to a x-y plane formed by the orientation of the microdevice) as it moves from fluid channel to fluid channel. The z-direction alignment step takes time and increases the chance of damaging the probe. For example, if a probe is inserted too far into a fluid channel, the probe may contact the fluid channel bottom surface potentially damaging the probe. In embodiments of the invention, the probe can be aligned in the z-direction once. To detect the characteristics of other fluid streams, the probe may move in an x- or y-direction while remaining a predetermined distance above the fluid channel bottoms. Also, by keeping the probe at a substantially constant z position, the reliability of measurements conducted by the probe can be improved in some instances. For example, the characteristics of a fluid flowing in a fluid channel may be a function of insertion depth in a fluid. Keeping a probe at a substantially constant z position when detecting characteristics of multiple fluids can eliminate any potential variation in any detected characteristics that may be due to different probe insertion depths. Furthermore, in embodiments of the invention, purging is not required between two successive detections (e.g., two successive measurements). In some conventional microfluidic devices, different fluids to be analyzed pass through a single fluid channel. Purging fluids are needed to separate the different fluids as they flow in series through the fluid channel. However, in embodiments of the invention, different fluids may flow in different, parallel fluid channels at a detection region in the microdevice. The fluids in the different fluid channels may be detected in series or in parallel without using purging fluids. Furthermore, the microdevice embodiments of the invention are especially suitable for use with biosensors. Typical biosensors may contain biological molecules such as lipids, enzymes, or receptors. If biological molecules such as these are exposed to air, they may become inactive. Moreover, a typical biosensor may have a variable “wetting” period after a sample fluid is applied to the biosensor. In embodiments of the invention, a probe can pass between different fluid streams without exposing the probe to an external environment such as air. Accordingly, the microdevice embodiments of the invention are especially useful for containing fluids that are to be analyzed using a biosensor. In addition, since fluid streams can contact each other yet not mix in an appreciable manner in embodiments of the invention, reactions at the interface of two flowing fluids may be analyzed. One or more probes may detect the characteristics of a fluid passing downstream of the interface of the two flowing fluids to study the interaction between the two fluids.
- A microdevice embodiment is shown in FIG. 1. FIG. 1 shows a
microdevice 10 comprising asubstrate 12, a plurality ofinner wall members 14 a-14 e, and a plurality ofouter wall members 14 o, 14 p. The plurality ofinner wall members 14 a-14 e is disposed between theouter wall members 14 o, 14 p. Both theinner wall members 14 a-14 e and theouter wall members 14 o, 14 p are disposed on thesubstrate 12. In this example, theinner wall members 14 a-14 e and theouter wall members 14 o, 14 p are substantially parallel to each other. - The
wall members 14 a-14 e, 14 o, 14 p are spaced so that each pair ofadjacent wall members 14 a-14 e, 14 o, 14 p produces a fluid channel 16 a-16 d. For example, adjacentinner wall members inner fluid channel 16 a. Theinner wall members outer wall members 14 o, 14 p form outerfluid channels 16 o, 16 p. For example,inner wall member 14 a andouter wall member 14 p form afluid channel 16 p. FIG. 2 shows a side view of the outer wall member 14 o and thesubstrate 12 of themicrodevice 10. In this example, the outer wall member 14 o is solid along its length and does not have an opening like theinner wall members 14 a-14 e. - The fluid channels16 a-d, 16 o, 16 p in the
microdevice 10 shown in FIG. 1 are substantially parallel to each other. However, in other embodiments of the invention, the fluid channels and the wall members forming those fluid channels may have any suitable configuration. For example, the fluid channels in the microdevice may be fabricated so that they are perpendicular or non-linear. Moreover, while themicrodevice 10 shown in FIG. 1 has six fluid channels, it is understood that in embodiments of the invention, themicrodevice 10 may have any suitable number of fluid channels. For example, in some embodiments, themicrodevice 10 may have more than 10, 20 or 50 fluid channels. - Each
inner wall member 14 a-14 e can structurally discontinue at an intermediate region to form anopening 20 a-20 e. Although the embodiment shown in FIG. 1 has oneopening 20 a-20 e perwall member 14 a-14 e, it is understood that embodiments of the invention are not limited to microdevices with one opening per wall member. For example, each wall member may have 2, 3, 4, or any suitable number of openings. Moreover, as will be explained in further detail below, in some embodiments, the wall members need not have any openings in them. - In some embodiments, the
openings 20 a-20 e in themembers 14 a-14 e may be aligned to form aslot 140. Theslot 140 formed by the alignedopenings 20 a-20 e can, for example, permit a probe (not shown) to pass from one fluid channel to another fluid channel without being removed from themicrodevice 10. Illustratively, a probe (not shown) can detect a characteristic of a first fluid flowing in afirst fluid channel 16 a. After detecting the characteristic, the probe may move through theopening 20 b and into asecond fluid channel 16 b. The probe may then detect a characteristic (e.g., pH, conductivity, fluorescence, and/or temperature) in a second fluid flowing in thesecond fluid channel 16 b without removing the probe from themicrodevice 10. Fluids in the otherfluid channels - Each
inner wall member 14 a-14 e can include one or more pairs of opposingbeveled structures 24 a-24 e that formopenings 20 a-20 e in therespective wall members 14 a-14 e. By using beveled structures in a wall member, a fluid having a laminar profile flowing in a fluid channel formed by the wall member is more likely to retain its laminar profile at the opening formed by the beveled structures. Thebeveled structures 24 a-24 e may have any suitable geometry. For example, two examples ofbeveled structures 24 a are shown in FIGS. 3(a), 3(b). - In FIG. 3(a), a
wall member 14 a includes abeveled structure 24 a. Thebeveled structure 24 a includes a pair of tapering walls 28 a. In this example, the tapering walls 28 a are substantially straight. Also, the tapering walls 28 a converge in an inward direction to an apex 30 and may form an angle with respect to substantially parallel side surfaces 114 a of thewall member 14 a. The angle may be, for example, from about 1 degree to about 89 degrees. In other embodiments, the angle may be, for example, about 2 to about 20 degrees. - FIG. 3(b) shows another example of a
beveled structure 24 a of awall member 14 a. Thebeveled structure 24 a also has a pair of tapering walls 28 a that converge to an apex 30. However, unlike the embodiment shown in FIG. 3(a), the beveled structure shown in FIG. 3(b) has curved tapering walls 28 a. In this example, the tapering walls 28(a) curve inwards towards the apex 30. Thebeveled structure 24 a shown in FIG. 3(b) has a generally funnel-shaped appearance when viewed from the top. Thebeveled structure 24 a shown in FIG. 3(c) is similar to the previously shown beveled structures, but includes a smooth transition between the side surfaces 114(a) and the tapering walls 28(a). As shown, side surfaces 114(a) may be substantially parallel to each other and may then gradually curve inwardly in the region of the tapering walls 28(a). - The particular geometries of the features of the
microdevice 10 may vary. Examples of features include wall member thicknesses, fluid channel heights, and fluid channel widths. Typically, the features of themicrodevice 10 have at least one dimension that is less than about 1000 microns. For example, in some embodiments, the width and depth of each fluid channel may be between about 10 microns and about 500 microns. In other embodiments, the width or depth of each fluid channel may be between about 50 microns and about 200 microns. In some embodiments, the fluid channels may sometimes be referred to as “microchannels”. - Referring to FIG. 4, each
wall member 14 a-14 e, 14 o, 14 p may have a width “W” of less than about 1 mm (e.g., about 20 microns to about 100 microns) and a height “D” of less than about 1 mm. In some embodiments, D may be from about 50 microns to about 500 microns (e.g., about 200 microns). Each fluid channel 16 a-16 d, 16 o, 16 p may have a width “w” of less than about 1 mm (e.g., about 50, 100, 150, or 200 microns). - Referring to FIG. 5, the distance “G” of each opening20 a formed in a
wall member 14 a may be about 1 mm or less. For example, in some embodiments, G may be from about 50 microns to about 400 microns (e.g., about 200 microns). As shown in FIG. 5, thewall member 14 a structurally discontinues to form anopening 20 a so that thewall member 14 a has two distinct, separated portions. Each portion of thewall member 14 a may have two parts. One part may have substantially parallel sidewalls and may have a length “L1” or “L2”. The other part may be a beveled structure that extends along the length of thewall member 14 a a distance “S”. Typically, the distance L1 or L2 is much greater than the length S. For example, the distance L1 or L2 may be about 1 cm or more (e.g., about 1 cm to about 5 cm). The length S may be about 50 microns to about 750 microns. Of course, the dimensions of the elements of themicrodevice 10 may have values that are more or less than the specifically mentioned values. - Again referring to FIG. 1, the fluid channels16 a-16 d, 16 o, 16 p may have any suitable length or configuration. The length of each fluid channel 16 a-16 d, 16 o, 16 p may be from about 1 to about 20 mm in length, or more. For example, the length of each fluid channel 16 a-16 d, 16 o, 16 p can be from about 2 to about 8 mm. The distance between the corresponding points (e.g., opposing apexes) of opposed beveled structures in a wall member may be between about 50 and about 500 microns in some embodiments. Any channel cross-section geometry (trapezoidal, rectangular, v-shaped, semicircular, etc.) can be employed in the
microdevice 10. Trapezoidal or rectangular cross-section geometries may be used in the fluid channels 16 a-16 d, 16 o, 16 p. Such geometries may be used with standard fluorescent detection methods. - Fluids such as liquids or gases may be supplied to the
microdevice 10 in any suitable manner. For example, bulk-loading dispensing devices can be used to load all fluid channels 16 a-16 d, 16 o, 16 p of themicrodevice 10 at once with the same or different fluids. Alternatively, integrated or non-integrated microcapillary dispensing devices may be used to load fluids separately into each fluid channel 16 a-16 d, 16 o, 16 p of themicrodevice 10. - The flow of the fluids within the fluid channels16 a-16 d, 16 o, 16 p can be controlled by the selective application of voltage, current, or electrical power to the substrate to induce and/or control the electrokinetic flow of the fluids. Alternatively or additionally, fluid flow may be induced mechanically through the application of, for example, differential pressure or acoustic energy to a fluid. Such fluid flow control mechanisms are used in microfluidic devices and are known in the art.
-
-
- Although the fluids in the channels preferably have a laminar profile, adjacent fluids flowing in adjacent fluid channels may slightly intermingle (e.g., by diffusion) via the opening that communicates the adjacent fluid channels. However, the degree of intermingling between fluids in adjacent fluid channels does not typically interfere with any measurements or detections made by a probe.
- Although many of the previously described examples have different sample fluids flowing through the fluid channels16 a-16 d, 16 o, 16 p in the
microdevice 10, in other embodiments of the invention, non-sample fluids such as wash fluids may be included in one or more of the fluid channels 16 a-16 d, 16 o, 16 p. For example, a wash fluid that can be used to wash a probe may flow through one or more fluid channels 16 a-16 d, 16 o, 16 p. For example, afluid channel 16 c containing a wash solution is disposed between twofluid channels fluid channel 16 b to detect a characteristic of a sample fluid flowing in thefluid channel 16 b. To detect a characteristic, the probe may be, for example, positioned influid channel 16 b between theopenings openings opening 20 c in thewall member 14 c to thefluid channel 16 c containing a wash fluid. In thefluid channel 16 c, the wash fluid removes any materials that may be disposed on the probe and that may impede the probe's ability to detect a characteristic in a different fluid. After the probe is washed, the washed probe may pass through theopening 20 d in thewall member 14 d to the otherfluid channel 16 d containing the other sample fluid. The washed probe can then detect a characteristic of the sample fluid in thefluid channel 16 d. Alternatively or additionally, one or more of the fluid channels 16 a-16 d, 16 o, 16 p may contain a calibration fluid that can be used to calibrate, for example, a probe. The probe can be calibrated while being disposed in a calibrating fluid and may move to a fluid channel with a sample fluid after the probe is calibrated. - FIG. 6 shows an analytical assembly comprising a
probe assembly 46 and amicrodevice 10. Themicrodevice 10 in FIG. 6 is similar to the previously describedmicrodevice 10 shown in FIG. 1, except that themicrodevice 10 shown in FIG. 6 includes acover 36. Thecover 36 may also comprise a plurality of fluid inlets (not shown) and a plurality of fluid outlets (not shown) that provide fluids to and remove fluids from the fluid channels 16 a-16 d, 16 o, 16 p in themicrodevice 10. - The
cover 36 is supported by the pair ofouter wall members 14 o, 14 p and may include aslot 40. A pair of opposed, generally parallel, boundaries may define theslot 40 in thecover 36. When thecover 36 is disposed on the wall members, theslot 40 in thecover 36 is aligned with and disposed over theslot 140 formed by theholes 20 a-20 e in theinner wall members 14 a-14 e (see FIG. 1). The boundaries defining theslot 40 in thecover 36 may or may not be generally aligned with apexes of the beveled structures in thewall members 14 a-14 e. Aprobe 44 of aprobe assembly 46 is inserted through theslot 40 in thecover 36 so that anend portion 47 of theprobe 44 is disposed in afluid channel 16 a and in theslot 140 inmicrodevice 10. - In the analytical assembly shown in FIG. 6, the
probe 44 may include anintermediate portion 45 that is upright and anend portion 47 that is skewed with respect to theintermediate portion 45. Theend portion 47 of theprobe 40 may be substantially perpendicular to theintermediate portion 45. In other embodiments, the end portion of the probe need not be perpendicular to an intermediate portion of the probe. For example, in some embodiments, the end portion of a probe may be co-linear with an intermediate portion of the probe. - In this example, the
end portion 47 of theprobe 44, is directed towards the upstream direction of the fluid flowing (which flows in direction A) through thefluid channel 16 a. As the fluid flows through thefluid channel 16 a, theend portion 47 of theprobe 44 may receive some of the fluid flowing in thefluid channel 16 a. Once the fluid is received, theend portion 47 may remove a portion of the fluid for sampling. For example, theprobe 44 associated with theprobe assembly 46 may include a micro-pipe that collects some of the fluid flowing through thefluid channel 16 a. Once collected, the sample may then be transferred to a mass spectrometer, HPLC (high pressure liquid chromatography) apparatus, or a gas chromatography apparatus. In some embodiments, the micro-pipe could also be used to introduce a fluid into a fluid channel. The introduced fluid can be added to a fluid channel without disturbing the laminar flow profile in the flowing fluid. Other suitable detection assemblies, detection devices, and analytical systems according to embodiments of the invention are described in further detail below. - Referring to FIGS. 6 and 7, to move the
probe 44 from fluid channel to fluid channel, theprobe 44 may move in the desired direction in theslot 40, such as in direction of arrow B (see FIG. 7). Because theend portion 47 in this example protrudes from theupright portion 45 of theprobe 44, in order to pass theend portion 47 through theslot 40, theend portion 47 may be initially aligned with theslot 40 and may then be inserted through theslot 40 in the cover (not shown in FIG. 7). Once theend portion 47 is in theslot 140 formed by theopenings 20 a-20 e in thewall members 14 a-14 e, it is rotated about 90° in direction of the arrow C shown in FIG. 7 so that theend portion 47 is directed toward the flowing fluid in the fluid channel in which it is disposed. Theboundary 40 a atslot 40 may be aligned with theapexes 30 a-30 e of thewall members 14 a-14 e so that theend portion 47 of theprobe 40 does not contact theapexes 30 a-30 e as theprobe 44 is inserted into theslot 40. - FIG. 8 shows another analytical assembly embodiment of the invention. In this embodiment, the
microdevice 10 includes acover 36 havingslot 40. Alid 50 is on thecover 36 and is spaced from thecover 36 by supports (not shown). Theslot 40 in thecover 36 is defined by downwardly sloping planar surfaces fromboundaries edges lid 50 also has aslot 60 that is generally aligned with theslot 40 in thecover 36. Theprobe 44 may pass through both theslot 60 in thelid 50 and theslot 40 in thecover 36. - The embodiment shown in FIG. 8 can be used when the fluids flowing through the fluid channels are gases. As gases flow through the fluid channels defined by the wall members and the substrate, another gas such as an inert gas (e.g., a noble gas, nitrogen, etc.) flows between the
lid 50 andcover 36. The inert gas may flow in a direction of the arrow D and may have a higher pressure than the gases flowing through the fluid channels formed by the wall members on thesubstrate 12. The higher pressure gas flowing between thelid 50 and thecover 36 confines gases flowing in the fluid channels between thecover 36 and thesubstrate 12 and prevents diffusion of the same out of the fluid channels and into the zone between thelid 50 and thecover 36. In the embodiment shown in FIG. 8, theprobe assembly 46 has aprobe 44 with a beveled end and not a protruding end portion as in the previous examples. The probe assembly in the embodiment shown in FIG. 8 could also have a protruding end portion if desired. - FIG. 9 shows another analytical assembly embodiment of the invention. The
microdevice 10 in this embodiment has asubstrate 12, abottom member 80, aslide member 90, acover 36, and aprobe assembly 46, and aprobe 44. Thebottom member 80 has apassage 82 where theslide member 90 is disposed. Theslide member 90 may slide in a direction transverse to the orientation of the fluid channels 16 a-16 e, 16 o, 16 p (i.e., in direction of the arrow E in FIGS. 10 and 11). As shown in FIGS. 10 and 11, thesubstances 94 disposed on theslide member 90 may be aligned with the fluid channels 16 a-16 e, 16 o, 16 p so that the fluids flowing within the fluid channels 16 a-16 e, 16 o, 16 p come in contact with thesubstances 94. - Illustratively, with reference to FIG. 9, the
slide member 90 may supportsubstances 94 that can contact a fluid flowing through thefluid channel 16 a prior to reaching theprobe 44 of theprobe assembly 46. The characteristic of the fluid in thefluid channel 16 a can be detected after the fluid has contacted thesubstances 94 on theslide member 90. For example, thesubstances 94 may comprise antibodies for capturing molecules contained in the fluid flowing in thefluid channel 16 a. Theprobe 44 may then contact the downstream fluid and theprobe 44 can detect a characteristic of the downstream fluid. The concentration of the molecules in the fluid can then be determined. If the concentration of the molecules upstream of theslide member 90 is greater than the concentration of the molecules downstream of theslide member 90, then it can be concluded that thesubstances 94 on theslide member 90 interact with the molecules in the fluid. - In some embodiments, the
microdevice 10 can be used to deposit successive layers of material on aslide member 90. This may be done by pulling theslide member 90 through thepassage 82 in themicrodevice 10. Theslide member 90 may be exposed to a succession of many different fluids that may deposit different materials on theslide member 90. - II. Detection Assemblies and Analytical Systems
- The detection methods, detection assemblies, and analytical systems used in embodiments of the invention are not limited to those described above, and may employ any suitable optical, electrical, physical, and/or chemical detection techniques. Radiation such as visible, infrared, or ultraviolet radiation from the fluids may be detected by a detection assembly being an optical detection assembly.
- In many of the embodiments described above, detection assemblies and analytical systems using probes that comprise micropipes are described in detail. However, embodiments of the invention are not limited to the use of such micropipes. For example, the end portion of a probe may contact the fluid flowing in a fluid channel to detect a particular characteristic of the fluid, without collecting a sample of the fluid. The probe may be coupled to signal analyzer (such as that sold by Hewlett-Packard, for example), an oscilloscope (such as that sold by Tektronix or Hewlett-Packard), or a lock-in amplifier (such as that commercially employed by Stanford Research System or EG&G).
- The probe may comprise a physical sensor, a biological sensor, a chemical sensor, or an electrical sensor. Examples of physical sensors include thermocouples, pressure sensors, flow sensors, optical fibers, etc. Examples of biological sensors include sensors with immobilized enzymes or immunoassays. Examples of electrical or chemical sensors include sensors with interdigitated electrodes having optional polymer coatings, atomic force microscopes (AFMs), Ion Sensitive Field Effect Transistors (ISFETs), light addressable potentiometric sensors (LAPSs), pH meters, and scanning probe potentiometers (SPPs). These and other types of sensors are described in Manalis et al,Applied Physics Letters, Volume 76, No. 8, Feb. 21, 2000, and other references. In comparison to optical detection devices, chemical sensors and electrical sensors are desirable as they do not need to use more expensive and inconvenient fluorescent or radiochemical tagging processes.
- An atomic force microscope allows high force sensitivity mapping of biological cells and molecules such as DNA and proteins. The AFM can obtain stable images of individual biomolecules while operating in physiological environments. In an AFM, unlike optical detection devices, molecules can be imaged directly, and the dimensions of the probe can determine the spatial resolution.
- Field effect devices such as the ISFET and the LAPS can directly detect molecular and ionic charge. For example, the LAPS device has been used in a microphysiometer to monitor the response of cells to chemical substances by measuring the rate of change of the pH as protons are excreted from cells during metabolism. LAPS devices may be commercially obtained from Molecular Devices of Sunnyvale, Calif.
- Preferably, the active areas of electrical detection devices such as AFMs, ISFETs, and SPPs are small. In some embodiments, the active area in such detection devices is less than about a square millimeter, or less than 100 square microns. When the active area is small, the detection sensitivity and resolution is improved in comparison to detection devices with larger active areas.
- Other detection devices may be used instead of or in addition to one or more probes. In some embodiments, detection devices such as one or more optical detection devices may be used to detect the characteristics of fluids flowing in the fluid channels in a microdevice. For example, FIG. 12 shows a schematic diagram of an analytical assembly comprising a detection assembly that detects fluorescent light coming from the fluids on a microdevice. In the illustrated detection assembly, the
microdevice 121 is positioned on abase plate 120. Light from a 100 Wmercury arc lamp 125 is directed though anexcitation filter 124 and onto abeam splitter 123. The light is then directed through alens 122, such as a Micro Nikkor 55 mm 1:2:8 lens and onto the fluids flowing in the fluid channels of the microdevice 110. Fluorescence emission from the device returns through thelens 122 and thebeam splitter 123. After also passing though anemission filter 126, the emission is received by a cooledCCD camera 127, such as the Slowscan TE/CCD-10245F&SB (Princeton Instruments). Thecamera 122 is operably connected to aCPU 128, which is, in turn, operably connected to aVCR 129 and monitor 130. - In some embodiments of the invention, the analytical assembly may comprise a detection assembly comprising a plurality of detection devices and a microdevice. The microdevice may comprise a plurality of wall members and a plurality of fluid channels, wherein each of the fluid channels is defined by adjacent wall members in the plurality of wall members. The analytical assembly may be used to detect characteristics of different fluids flowing in different fluid channels substantially simultaneously. In these embodiments, the wall members of the microdevice may or may not have openings that allow adjacent fluid channels to communicate with each other. By using multiple detection devices, the characteristics of fluid flowing in the fluid channels of a microdevice may be detected in parallel, thus increasing the speed of detection and analysis.
- In one example, a plurality of different biological moieties can be screened in parallel for their ability to interact with a component of a fluid sample. A fluid sample can be delivered to the reactive sites in fluid channels in a microdevice where each of the different biological moieties is immobilized on a different site of the microdevice. Then, characteristics of the fluids passing downstream of the reactive sites may be detected substantially in parallel with a plurality of detection devices to study the interaction of the component with the immobilized biological moieties at each reactive site.
- Illustratively, referring to FIG. 13, a
slide member 90 may comprise a number of detection devices such assensors 194 and may form a detection assembly. Thesensors 194 on theslide member 90 may contact the fluids flowing in the fluid channels 16 a-16 e, 16 o, 16 p and may subsequently detect characteristics of the fluids. Thesensors 194 may be, for example, conductivity sensors, biosensors, temperature sensors, etc. In these embodiments, a probe assembly with an elongated probe, and a cover with a slot for the elongated probe are not needed. - Other detection assemblies with multiple detection devices may be used in embodiments of the invention. For example, probe assemblies like the
probe assembly 46 shown in FIG. 6 can be used. The probe assembly, however, may comprise two or moreelongated probes 44. These probes may be spaced so that they can be inserted into plural fluid channels simultaneously to detect characteristics of the fluids flowing in these fluid channels substantially simultaneously. In some embodiments, the number of probes in the detection assembly may be equal to or less than the number of fluid channels in the microdevice. For example, if a microdevice has six fluid channels, a probe assembly with six probes that are insertable within the six fluid channels can be used to substantially simultaneously detect characteristics of the six fluids flowing in the six fluid channels. - In another example, a plurality of optical detectors may be positioned to receive optical signals coming from a plurality of fluids flowing in their respective fluid channels on a microdevice. For example, the plurality of optical detectors may comprise a charge coupled device (CCD) array or a photodiode array. These arrays may be positioned to receive optical signals coming from the fluids flowing in the fluid channels. In some embodiments, radiolabels or fluorescent tags on molecules in fluids flowing in the fluid channels in a microdevice may provide such optical signals.
- III. Exemplary Methods of Manufacture
- The microdevices according to embodiments of the invention may be made according to any suitable process. For example, in some embodiments, portions of a body of material may be removed to form a plurality of wall members. In these embodiments, the wall members may be integrally formed with the substrate. Examples of suitable material removal processes include bulk micromachining, sacrificial micromachining, focused ion-beam milling, electrostatic discharge machining, ultrasonic drilling, laser ablation, mechanical milling and thermal molding techniques. Conventional photolithographic and etching processes may be used to etch a body to form a plurality of wall members and fluid channels in the body. Etching processes such as reactive ion etching (RIE) or deep reactive ion etching (DRIE), or wet etching may be used to etch an appropriate body of material. In some embodiments, the wall members and the underlying substrate may be formed by molding. In other embodiments, wall members may be formed on a substrate. For example, wall members may be formed on or bonded to a body to form a plurality of fluid channels. For example, wall members may be formed by electroplating (e.g., high aspect ratio plating).
- If desired, after the fluid channels are formed in the microdevice, the surfaces defining the fluid channels may be coated with a material. The material coated on the walls or bottom surfaces defining the channels may be an adhesion layer, coupling agents, or substances that may potentially interact with fluids flowing through the fluid channels.
- Any suitable material may be used as to form the substrate and the wall members in the microdevice. The materials used may be organic or inorganic, and may be transparent, translucent, or non-transparent. Materials that can be micromachined or microfabricated are preferred. Suitable micromachinable materials include silicon, glass, plastic and the like. Other suitable materials, and processes for forming a plurality of fluid channels in a microdevice may be found in U.S. patent application Ser. No. 09/115,397, which is assigned to the same assignee as the present application, and International Application No. PCT/US99/15968. Both of these applications are herein incorporated by reference in their entirety for all purposes.
- A microdevice having ten fluid channels was fabricated by forming nine wall members in a silicon substrate. The wall members were formed in a silicon substrate using a deep reactive ion etch. Each of the wall members had an opening and the openings in the wall members were aligned to form a slot that passed across the nine wall members. The height of the wall members and the corresponding channel depth was about 200 microns. The width of each of the fluid channels was 110 microns, and the channel pitch was about 150 microns.
- Buffered solutions with pH values of 4, 7, and 10 were fed to the different fluid channels in the microdevice. Because the fluid channel volumes were low, the Reynolds number for the solutions in the fluid channels was sufficiently low to maintain laminar flow at reasonable flow rates. With laminar flow, the solutions flowing in the ten fluid channels did not mix in the slot region of the microdevice. The flow rates for the solutions in the fluid channels were set for a maximum value of 500 nanoliters/minute.
- The pH values of the different fluids flowing in the ten fluid channels were measured using a scanning probe potentiometer (SPP). The SPP had a probe was insertable into a fluid channel and had a sensitivity of less than 0.01 pH units and a spatial resolution of 10 microns.
- The pH of the ten fluids flowing in the ten fluid channels was profiled by measuring the pH in a fluid channel proximate one side of the microdevice. After the pH values in this fluid channel are measured, the probe moves through the slot to the next adjacent fluid channel without removing the pH sensitive area of the probe from the flowing fluids. The pH value of the adjacent fluid channel was then measured. The pH values of the fluids in the remaining eight fluid channels were measured in a similar manner. The travel time between the fluid channels was about 1 second. The measurement time was about 5 seconds per channel.
- A plot of sensor potential versus time during the scanning process is shown in FIG. 14. The relative potential difference between each fluid channel correlates closely to the actual pH values of the fluids in the channels (listed above the plot), except for the first and last edge channels. Each of the plateaus in the plot corresponds to a pH measurement of a fluid in a fluid channel. As shown in the plot, the time used to measure the pH values of the ten fluids in the ten fluid channels was less than one minute.
- All patents, patent applications, and publications mentioned above are herein incorporated by reference in their entirety. The citation of such documents is not an admission such patents, patent applications, and publications are prior art.
- The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed. Moreover, any one or more features of any embodiment of the invention may be combined with any one or more other features of any other embodiment of the invention, without departing from the scope of the invention. For example, any feature of the embodiments using multiple detection devices may be used with any feature of the embodiments using wall members with openings without departing from the scope of the invention.
Claims (28)
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US7615190B2 (en) | 2009-11-10 |
US6794197B1 (en) | 2004-09-21 |
US20040197931A1 (en) | 2004-10-07 |
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