WO2014154711A1

WO2014154711A1 - Method for producing an object comprising at least one thread, said object being made of a hardened inorganic or organic material

Info

Publication number: WO2014154711A1
Application number: PCT/EP2014/055990
Authority: WO
Inventors: Tarek Fathallah
Original assignee: Commissariat à l'énergie atomique et aux énergies alternatives
Priority date: 2013-03-28
Filing date: 2014-03-25
Publication date: 2014-10-02
Also published as: FR3003789A1; FR3003789B1

Abstract

The invention relates to a method for producing a moulded object comprising at least one thread, said object being made of a hardened organic or inorganic material, said method successively comprising the following steps: a) a step of entirely filling the inner cavity (29) of a mould (27), said inner cavity (29) having a shape corresponding to that of the desired object (37), with a liquid composition (33) hardenable by chemical reaction in order to form said hardened organic or inorganic material, said composition comprising a solvent; b) a step of hardening said composition by chemical reaction inside said mould; and c) a step of drying, inside said mould, the object (37) produced in b).

Description

METHOD FOR MANUFACTURING AN OBJECT COMPRISING AT LEAST ONE FILET, SUCH OBJECT BEING IN A CURED INORGANIC OR ORGANIC MATERIAL

DESCRIPTION TECHNICAL FIELD

The present invention relates to a process for manufacturing an object molded from an inorganic or organic hardened material, said object comprising at least one net, said process being carried out in a medium comprising at least one solvent, in particular an organic solvent, water or a mixture comprising water and an organic solvent, said hardened inorganic material being conventionally a material resulting from a sol-gel process, whereas the hardened organic material is conventionally a polymeric organic material.

This method can find application in the manufacture of objects for the field of detection, such as optical detection, electrical detection, these objects can thus constitute waveguides. In such applications, the object is intended to be contacted with an analyte circulating in a fluid along said net. The presence of the net then makes it possible to increase the surface of the object that can be brought into contact with the analyte, whereby the detection efficiency is increased.

STATE OF THE PRIOR ART

The preparation of an object made of an organic polymeric material can take place mainly according to two processes, which are as follows:

polymerization chain; and

the stepwise polymerization, such as polycondensation.

In the context of the polymerization chain, this involves at least one step of polymerization of precursors of the material, these precursors may be monomers or oligomers that will react together, after having formed active centers (such as radicals or ions ), to form constituent polymeric chains of said material. In the context of the stepwise polymerization, this involves at least one step of polymerization of precursors of the material by reaction between functional groups carried by these precursors, one of the classic examples of the step polymerization being polycondensation.

As a variant, the preparation of an object made of a polymeric material may involve, in place of a polymerization step stricto sensu, a step of crosslinking of pre-existing polymeric chains, which means, in other words, that these chains At the end of this crosslinking step, the polymers will form a three-dimensional network consisting of polymer chains linked to one another via crosslinking bridges. In other words, the pre-existing polymer chains comprise functions that are capable of reacting with a crosslinking agent during the crosslinking step, to form said three-dimensional network (this is known as chemical crosslinking) or else comprise functions capable of reacting between them, spontaneously or following a physical stimulation (one speaks then of physical cross-linking).

Whether for the polymerization step or the crosslinking step, when they are carried out in a medium comprising a solvent, the object resulting from these steps is an object, which can trap, within it, at least one part of the solvent, which must be removed to complete the realization of the object.

Drying techniques, such as evaporative drying, produce a dry (i.e., solvent-free) object, which can be disadvantageously cracked and cracked due to the presence of high surface tension. at the level of the pores trapping the solvent. Moreover, when this technique is implemented with a polymerizable solution cast in an open mold on the outside (when it is particularly necessary to produce an object of more complex shape than a monolith), it turns out that the drying of the object is not homogeneous in all directions, which can lead to an object whose shape does not match the original mold. Finally, non-homogeneous drying of the object induces, moreover, additional mechanical stresses, which promote the appearance of cracks within the object. As for the preparation of a sol-gel object, it consists in preparing a solution containing precursors based on metal or metalloid elements (which may be organometallic compounds or metal salts) and one or more solvents. organic, the resulting solution thus forming a soil (which can also be called sol-gel solution). Due to the addition of water to the formulation, the precursors contained in this sol-gel solution undergo, in part, a hydrolysis step and a condensation step, to form an oxide network trapping the solvent, so as to form a gel. The gel is then dried, to form at the end of this drying a monolithic object.

At present, two drying techniques predominate:

evaporative drying; and

supercritical drying.

Evaporative drying consists of removing the organic solvent or solvents present in the sol-gel solution by heating at atmospheric pressure or under reduced pressure (ie, a pressure below atmospheric pressure). At the end of this drying, a dry gel (also called xerogel) is obtained in the form of a porous monolith, which can disadvantageously present cracks and fissures due to the presence of high tensions. superficial in the pores. Moreover, when this technique is implemented with a sol-gel solution cast in an open mold on the outside (when it is particularly necessary to make an object of more complex shape than a monolith), it is shows that the drying of the gel is not homogeneous in all directions, which can lead to an object whose shape does not match the original mold. Finally, non-homogeneous drying of the gel induces, moreover, additional mechanical stresses, which favor the appearance of cracks within the object.

As for the supercritical drying, it consists, as its name suggests, in subjecting the sol-gel solution to supercritical conditions, whereby the gas phase and the liquid phase become indistinguishable. This drying principle is used, in particular, in the process described in US Pat. No. 7,216,509. If this drying technique can make it possible to obtain a drying of the object in its mold without volume shrinkage, the use of an open mold on the outside does not however make it possible to obtain a control on all the faces of the mold. object obtained, especially on the face which is directly in contact with the outside.

Thus, in summary, whether for the polymerization, the crosslinking or the sol-gel route, when they are carried out in a medium comprising a solvent, the drying of the object is conventionally not homogeneous in all directions; which can lead to an object whose shape does not correspond to the original mold, which prevents the manufacture of objects of complex shape. Finally, non-homogeneous drying of the object induces, moreover, additional mechanical stresses, which promote the appearance of cracks within the object.

In view of what exists, the authors of the present invention have therefore set themselves the objective of proposing a method of manufacturing a molded object of specific shape of a hardened inorganic or organic material not having the aforementioned drawbacks, namely, in particular, the disadvantages associated with a non-uniform drying which induces a deformation of the object with respect to the shape that it is initially desired to obtain as well as a non-homogeneous microstructure.

STATEMENT OF THE INVENTION

To overcome these drawbacks, the authors of the present invention propose a method of manufacturing a molded object comprising at least one thread, said object being made of a hardened organic or inorganic material, said method comprising successively the following steps:

a) a step of completely filling the internal cavity of a mold, said internal cavity having a shape corresponding to that of the object, which it is desired to obtain, by a liquid composition curable by chemical reaction to form said organic material or hardened inorganic, said composition comprising a solvent;

b) a step of hardening by chemical reaction of said composition within said mold;

c) a drying step within said mold of the object obtained in b), characterized in that said mold, at least during the implementation of step c), is a closed chamber, whose walls forming a boundary between the internal cavity and the outside of the mold are in at least one material suitable for allow the evacuation of the gases from step c) and possibly step b).

Before going into more detail in the description of the invention, we specify the following definitions.

"Mold consisting of a closed chamber" means a mold, the internal cavity of which is not in direct communication with the outside of said mold (or, in other words, with the ambient atmosphere of said mold) at less during the implementation of step c), which means, in other words that the internal cavity is isolated from the ambient atmosphere surrounding said mold at least during the implementation of step c ). Moreover, the walls forming a boundary between the internal cavity and the outside of the mold are made of a material capable of evacuating the gases resulting from stage c) and possibly from stage b) (these gases being derived, in any case or part of the evaporation of the solvent or solvents), which allows homogeneous evacuation of said gases at all the external faces of the object. This results in a uniform control of the dimensions of the object.

The mold may comprise, within the internal cavity, several separate compartments, which allows the realization of objects of complex shape. This is the case, in particular, when the mold comprises, within said internal cavity, inserts, such as removable parts, such as parts in the form of cylinders or integrated beams for producing objects that may have holes. corresponding to the shape of the elements reported. In this case, it can be provided a withdrawal system of these inserts with or without opening the mold, it being understood that the mold must be a closed enclosure at least during the implementation of step c).

The mold may further comprise at least one inlet port allowing communication between the outside and the internal cavity, with a view to implementing step a), it being understood that this orifice will be closed in order to of the setting at least in step c), preferably using a material capable of allowing the evacuation of the gases produced during step c) and possibly step b).

As mentioned above, the mold is a closed-chamber specific mold as defined above at least for the implementation of step c). In the same way, it can be applied for the implementation of step b) (in particular, when steps b) and c) take place simultaneously) or even for the implementation of step a ), in which case step a) can be implemented, as will be explained below, by introducing a syringe comprising the curable composition into the inner cavity of the mold by simply passing through the wall. A mold adapted to this case is a mold consisting of a closed chamber formed of a single block (also called monobloc), whose walls delimiting the internal cavity of the outside consist solely of a block of said material able to evacuate the gases formed during step c) and possibly step b). It is understood that the material capable of evacuating the gases formed during step c) and possibly during step b) is an integral part of the mold and thus does not result from a filler element, such as a lid added later.

Through the use of a closed-chamber mold (at least for the implementation of step c)) whose walls delimiting the internal cavity of the outside of the mold are made of a material able to evacuate the formed gases during step c) and optionally step b), the method of the invention fills the gaps encountered in the processes of the prior art and makes it possible in particular to obtain:

objects capable of having a complex geometry on all sides;

a control of the drying making it possible to standardize the latter, which results in a uniform retraction of the hardened object and thus a respect for the relative ribs of the object that one wishes to obtain with respect to the mold of this object and this also translates into better control of the microstructural features of the object; in other words, the method of the invention allows retention of the proportionality between the dimensions of the object, when the object contracts under the effect of drying; and a confinement of the atmosphere existing in the mold, which makes it possible to preserve the object from the outside and thus to prevent any cracking and also to effect drying at a pressure below atmospheric pressure and therefore decrease the duration of this drying.

Preferably, the thickness of the walls of the mold is identical over the entire mold, which ensures a uniform drying rate at all points of the mold.

By object comprising a net is meant an object having a helical structure, for example, wound around a solid cylinder (in which case the object may be called a threaded rod, such as a screw-shaped object) or rolled up. in the hollow of a cylinder (in which case the object can be called a tapped hole, such as a nut-shaped object).

As mentioned above, the method of the invention comprises a step of completely filling the inner cavity of the mold with a curable composition intended to constitute the material constituting the aforementioned object.

This step a) is, conventionally, by injecting said composition into the internal cavity of the mold until complete filling thereof, for example, via a syringe passing through the wall of the mold (especially when the mold is based on an elastomeric material), this step a) being able to be done in several times, in particular, when the internal cavity of the mold is divided into several compartments.

During the implementation of step a), the mold may be a closed-chamber mold, in particular when the walls of the mold are made of an elastomeric material, which allows the introduction of a syringe into the internal cavity without opening. of the mold, the elastomeric material retracting during withdrawal of the syringe, which keeps the closed chamber mold for at least the implementation of step c).

The walls forming a boundary between the internal cavity and the outside of the mold are made of a material capable of allowing the evacuation of the gases produced during step c) and possibly of step b), these gases being, in particular, those resulting from the evaporation of the solvent during the aforementioned drying step. They can also result from other products of the reaction mixture, such as by-products from the curing step.

A material meeting these specificities may be an elastomeric material, for example an elastomeric material of the family of polysiloxanes.

More particularly, such a material may be an elastomeric material belonging to the family of polydimethylsiloxanes, this family being characterized by the presence of a sequence of repeating units of formula (I) below:

(I)

In addition to the ability to allow the evacuation of gases from step c) and possibly from step b), such as the gases resulting from the evaporation of the organic solvent or solvents, the elastomeric materials have the advantage of absorbing the mechanical stresses generated during the curing step and the drying step. On the other hand, these elastomeric materials have excellent molding properties, which makes it possible to perfectly respect the dimensions of the initial object.

Certain elastomeric materials, as is the case with polydimethylsiloxanes, are transparent to UV rays, which makes them interesting when it is desired to induce by UV rays the polymerization or crosslinking of the composition introduced into the mold during step a) .

The mold may be based on other organic materials than those mentioned above or other inorganic materials, provided that they are capable of allowing evacuation of the gases produced during at least the drying step.

Prior to step a), the method of the invention may comprise a step of preparing the mold of the object to be manufactured.

This preparation step may consist in molding a piece of shape corresponding to the object that one wishes to manufacture, whereby it results from this stage a mold having an internal cavity having the shape of the object to be manufactured (here, an object comprising at least one thread), it being understood that the walls delimiting the outside of the mold of the internal cavity thereof are in one material capable of allowing the evacuation of the gases formed during step c) and possibly step b).

Depending on the nature of the constituent material of the mold, this preparation step can take place according to different variants.

For example, when the mold comprises a polydimethylsiloxane material, the mold preparation step may comprise the following operations:

an operation of bringing into contact a piece of shape corresponding to the object that it is desired to manufacture with a solution comprising:

a polymer comprising, in its main chain, a repeating unit sequence of formula (I) as defined above and at least two ethylenic end groups; and

a crosslinking agent;

an operation for crosslinking said solution;

a removal operation of the starting piece, whereby it remains said mold comprising an internal cavity whose shape corresponds to the impression of the original part.

The contacting operation can be carried out in a container in which the above-mentioned part is placed, this container being filled with a solution as defined above.

The aforementioned polymer may correspond to a polymer of formula (II) below:

(M) where n is the repetition number of the repeating pattern taken in square brackets. The crosslinking agent can be of various types.

In the case of hot crosslinking, the crosslinking agent may be one or more organic peroxides, such as benzoyl peroxide, dicumyl peroxide and mixtures thereof.

When it comes to cold crosslinking, which is particularly the case with two-component elastomers, the crosslinking agent may be:

a tetrafunctional alkyl silicate in the presence of an organostannous catalyst and a platinum salt;

a crosslinking agent of the R-SiX ₃ or SiX _{4 type} in the presence of a metal salt, in which R may be an alkyl group and X may be a hydrolysable group, such as an acetoxy, alkoxy, amino or amido group.

The aforementioned solution may be commercially available, for example, in the form of a kit comprising two parts, a first part comprising said polymer and a second part comprising said crosslinking agent, these two parts to be mixed to form the solution.

The crosslinking operation may consist, when the crosslinking is to be carried out hot, to heat the assembly formed by the part and the solution to a suitable temperature and duration (it is called, then thermrocellulation) to obtain the transformation of the solution in a solid material surrounding the piece of shape corresponding to the object that one wishes to manufacture.

The crosslinking operation can also be carried out at room temperature, when the crosslinking can be carried out cold.

At the end of this crosslinking operation, the part is removed so as to leave only the mold of the object to be manufactured. This removal operation may be preceded by a cutting operation of the solid material in at least two parts so as to remove the piece. In this case, it is understood that the cut parts will be reassembled after removal of the part, while sparing, if necessary is an entry for the subsequent introduction of the curable composition into the mold.

It is also possible to envisage the manufacture of the mold in several distinct parts (for example, in two parts), to assemble these parts by simple mechanical pressure or by electromagnetism and to disassemble these parts without it being necessary to proceed to a cutting operation.

As mentioned above, it is introduced into the internal cavity until complete filling of the latter, a liquid composition curable by chemical reaction.

This liquid composition curable by chemical reaction can be:

a polymerizable and / or crosslinkable organic composition, in which case the final material of the object will be a polymerized or polymeric organic material; or

a composition consisting of a sol-gel solution, to which the final material of the object will be a sol-gel material.

This composition may also be prepared prior to step a).

When this composition is a polymerizable and / or crosslinkable composition, this preparation step may consist in bringing into contact the ingredients necessary for the manufacture of a polymerized or polymeric organic material in a solvent medium.

More specifically, when the composition is a polymerizable organic composition, the reagents contained in this composition can be:

at least one polymerizable monomer;

optionally, at least one polymerization initiator; and

at least one solvent, for example an organic solvent, water or a mixture comprising water and an organic solvent.

When the polymerization is carried out according to a so-called "chain" radical mechanism, vinyl monomers, that is to say monomers comprising at least one carbon-carbon double bond, may be mentioned as monomers, such monomers being olefinic monomers, monomers styrenics, (meth) acrylate monomers (such as methacrylic acid, ethylene glycol dimethacrylate).

As a polymerization initiator, it may be, in particular, a free radical initiator (in particular, when the polymerization proceeds by a radical mechanism), such as nitrile compounds such as azoisobutyronitrile (symbolized by the abbreviation AiBN).

When the polymerization is carried out according to a stepwise polymerization mechanism, the monomers used may be monomer pairs such as:

a pair comprising at least one diamine monomer and at least one dicarboxylic monomer;

a pair comprising at least one monomer carrying at least one -OH group (for example, resorcinol) and at least one monomer bearing at least one aldehyde group (for example, formaldehyde).

Finally, when the composition is a crosslinkable composition, it may comprise:

at least one polymer comprising at least one crosslinkable functional group;

a crosslinking agent, when the crosslinking is carried out chemically and not physically; and

Those skilled in the art, depending on the material constituting the object to be manufactured, will suitably choose the ingredients necessary for the manufacture of said object, whether in terms of monomers, possible polymerization initiators, solvents , crosslinkable polymers, optional crosslinking agents.

In addition to the presence of the aforementioned ingredients and one or more solvents, the composition may comprise other adjuvants, such as:

-the water ; catalysts for accelerating the polymerization and / or crosslinking reaction;

organic or inorganic pigments;

organic compounds with optical properties, such as fluorophore compounds, phosphorescent compounds, anti-UV agents, antireflection agents or compounds having a function that is reactive with analytes (for the purpose of ensuring, for example, the detection of 'analytes); and

more specifically, compounds capable of facilitating the detection of compounds, such as those described in FR 2 960 799.

When the composition is a sol-gel solution, this preparation step may consist in bringing into contact one or more molecular precursors of metal or metalloid with a medium comprising one or more organic solvents and optionally other adjuvants, such as water, a catalyst.

The metal may be selected from a group consisting of transition metals, lanthanide metals and so-called post-transitional metals of columns NIA and IVA of the Periodic Table of Elements. The transition metal element may be selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt. The lanthanide element may be chosen from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb. The post-transitional metal element may be chosen from the elements of the NIA group Al, Ga, In and TI and the elements of group IVA Ge, Sn and Pb.

The metalloid element is advantageously chosen from Si, Se and Te.

It can also be any combination of transition metals, lanthanide metals, post-transition metals and metalloids.

Molecular precursors of metal or metalloid may be in the form of inorganic metal or metalloid salts such as halides (fluorides, chlorides, bromides, iodides), alkaline salts (such as, for example, sodium silicate).

The molecular precursors of metal or metalloid may also be in the form of organometallic compounds of metal or metalloid, such as, in particular, alkoxides, for example those having the formula (RO) _n M, in which M denotes the metal or the metalloid, n represents the number of ligands bonded to M, this number also corresponds to the degree of oxidation of M and R represents a linear or branched alkyl group which may contain from 1 to 10 carbon atoms; carbon or a phenyl group.

Molecular precursors of metal or metalloid, as described above, are contacted with a medium comprising an organic solvent, so as to form a sol-gel solution.

Preferably, the solvent is an organic solvent chosen from:

saturated or unsaturated aliphatic or aromatic monoalcohols, for example those of formula R ¹ -OH, in which R ¹ represents a linear or branched alkyl group comprising from 1 to 30 carbon atoms, preferably from 1 to 10 atoms carbon or a phenyl group;

diols, for example those having the formula HO-R ² -OH, in which R ² represents a linear or branched alkylene group comprising from 1 to 30 carbon atoms, preferably from 1 to 10 carbon atoms, or a phenylene group.

As examples of diols, mention may be made of ethylene glycol, diethylene glycol or else triethylene glycol.

In addition to the presence of one or more molecular precursors and one or more organic solvents, the sol-gel solution may comprise other adjuvants, such as:

water, which can contribute to facilitating the gelling process of the sol-gel solution;

catalysts making it possible to accelerate the kinetics of the hydrolysis and condensation reactions during the transformation of the sol-gel solution into a gel (these catalysts can be an inorganic acid, such as hydrochloric acid, an organic acid, such as as acetic acid);

organic or inorganic pigments;

organic compounds with optical properties, such as fluorophore compounds, phosphorescent compounds, anti-UV agents, anti-reflective agents or compounds having a reactive function with analytes (to ensure, for example, the detection of analytes);

Prior to step a), the mold may be subjected to a treatment step of its inner surface (i.e. the surface of the internal cavity intended to be in contact with the curable composition), so to minimize the adhesion of the cured object and thus facilitate the removal of this object from the mold. It is understood that this treatment must not modify, or in any case not substantially, the permeability of the mold vis-à-vis the gas. This surface treatment step may consist of hydrophobic silanization of the inner surface of the mold (for example, by means of reagents such as a perfluorinated silane, trichloromethylsilane).

The mold, in which the composition is introduced, can be fixed on a mobile system, for example rotary, which will make it possible to obtain objects of better quality, the movement induced by the system, for example, a rotational movement, to avoid a phenomenon of collapse of the hardened material during the drying process or in other words to counter the effect of gravity. Advantageously, the mobile system is operated only after the introduction of the composition and after the curing of the composition concomitantly with the implementation in the drying step c). This applied movement can also contribute to facilitating the subsequent demolding operation especially for microstructured objects in contact with one of the faces of the mold, in particular the lower face, the viscoelasticity of the mold being able to absorb shocks during the step rotary drying.

Once step a) has been completed, the method comprises a step of hardening by chemical reaction of the composition introduced into said mold.

If the curable composition is a polymerizable and / or crosslinkable composition, the curing step will consist of a polymerization and / or crosslinking step, while, if the curable composition is a sol-gel solution, the curing step will consist of a gelling step of the sol-gel solution. From a practical point of view, this step may consist in placing the mold thus filled at rest for a time and a temperature sufficient for the transformation of the sol-gel solution into a gel or at a temperature and duration suitable for cause polymerization or crosslinking of the composition. This time and temperature can be determined by those skilled in the art by routine experiments and can vary in particular depending on the volume of the composition, proportions and amounts of ingredients used in this composition. Preferably, the duration of this step is short, in particular less than 20 minutes, and preferably less than 5 minutes, so as to limit the evaporation of the solvent during this step. Indeed, if the aforementioned step is slow (ie, if the fixed time is long), it could lead to a deformation of the polymer and thus a form thereof that does not conform to the internal cavity of the mold.

Furthermore, for the implementation of the polymerization or crosslinking step, the mold can be placed in an environment, which limits the evaporation of the solvent through the wall of the mold, such an environment can consist of an enclosed space saturated with solvent vapor or can be obtained by lowering the temperature.

After step b), the process of the invention comprises a drying step (step c), whereby the gases (including those resulting from the evaporation of the solvent or solvents) are removed by evaporation through the walls of the mold. .

This drying step can be carried out simultaneously in step b) or, at the very least, can start while step b) is not completed.

This drying step may be carried out according to various variants, among which may be mentioned:

supercritical fluid drying, such as supercritical carbon dioxide;

drying by heating;

vacuum drying;

drying under a controlled atmosphere; and

a combination of the above-mentioned drying methods. It is not excluded that the drying step can be implemented by a combination of the aforementioned variants. In particular, when the drying step combines both heating drying and vacuum drying, this can substantially reduce the drying time or the drying temperature compared to heating drying.

By way of example, the drying step may include placing the mold in a rotary kiln and heating the mold to a suitable temperature and duration (eg, 45 ° C for 5 days) to allow removal by evaporation of the solvent or solvents, this heating can be combined with a vacuum, the gases from the evaporation through the walls of the mold.

In addition, at the end of the process, it is conventionally implemented a step of removing the mold object, this removal step can be done by cutting the mold so as to release the object.

The object obtained according to the method of the invention has, compared to the mold, dimensions consistent with the original part without deformation of its shape. In other words, the relative proportions are conserved.

The object formed by the process of the invention can in turn be used as a model to form a mold, which can be used, then, in a process comprising steps according to the invention (steps a), b) and c) above), these operations can be repeated as many times as possible until an object having the desired dimensions is obtained. This may be particularly advantageous for producing microstructured micrometric objects, without having to resort to microstructuring means.

The constituent material of the object is a polymeric material (such as a xerogel, an airgel), when the starting composition is a polymerizable and / or crosslinkable composition, while the material constituting the object is a solid material. gel (such as a xerogel, an airgel) resulting from the drying of the gel, this material can be converted into ceramic or glass by a subsequent heat treatment.

With regard to the production of microstructured devices, thanks to the method of the invention, it is thus possible to avoid the use of microstructuring such as etching, the latter may leave a state of uncontrolled surface.

For that :

a microstructured piece is used, intended to be reproduced, so as to form a mold;

this part is reproduced by the method of the invention, which makes it possible to obtain a part having microstructures with reduced dimensions.

It is possible to repeat these operations, forming a mold from the piece previously obtained by the method of the invention. By multiplying the iterations, it is possible to obtain a micrometric part without having to resort to means of microstructuring.

In addition to the advantages already mentioned above, the method of the invention is also easy to implement.

Because of its shape which makes it possible to confer a large active surface area, the object resulting from the process of the invention can naturally find its application in the field of detection, in particular the detection of an analyte circulating in a fluid. , along the net. The fluid can be a liquid or a gas. In particular, the material constituting the object may be able to capture said analyte, which causes the modification of its optical properties (such as coloring, fluorescence). The realized object can be used as a sensor, whose detection surface (or more precisely, the active surface) is the helix described by the net. This detection surface, subjected to the scanning of the fluid, confers a high contact surface between the analyte and the object to capture the analyte. This helps to improve the detection efficiency of the sensor.

For example, the material constituting the object may be porous.

The object can advantageously be arranged between a light source and a detector, the detector being able to detect the light signal transmitted by the object, when the latter is subjected to illumination by the light source. The object then serves as a waveguide. The method of the invention can therefore be used to design sensors for guiding electromagnetic waves. More specifically, the objects acting as waveguides are made using a material obtained by the sol-gel technique or by polymerization and / or crosslinking according to the method of the invention.

The modification of the optical properties of the object may be due either to the material constituting the object or to the presence within the material of chemical sensors.

For example, if an object in the form of a screw having an average diameter of 4.5 mm, a length of 10 mm and an average perimeter of 14.13 mm is used, the path traveled by a gas or Liquid snaking in the thread of the screw is (10 * 14,13) +10 mm, or 141.4 mm, or a gain of a factor 14 compared to an unthreaded rod and other dimensions equal. This gain can be significantly greater, if one takes into account in the calculation of the improvement induced by the confinement of the fluid in contact with the object.

The flow of the fluid (gas or liquid) along the thread can be facilitated by a confinement element, intended to be applied opposite the thread, so as to define a fluidic channel, in which the fluid, comprising the analyte, can circulate. Injection or suction means may be arranged upstream or downstream of this channel, to facilitate the flow.

Thus an aspect of the invention is a device for capturing an analyte present in a fluid comprising:

an object made of a hardened organic or inorganic material capable of capturing said analyte, said object being advantageously produced by the method of the invention as defined above;

a confinement element, for example an enclosure surrounding said object, capable of defining a fluidic channel for the flow of said fluid along the object, and in particular along the net.

Thus, the device can act as an extractor or concentrator of the analyte from the fluid to the object. It can then be used to purify the fluid (for example, a gas or a liquid) of certain molecules, macromolecules or even pathogenic organisms (such as bacteria, viruses). The device may also act as a detector of said analyte, in which case it will also comprise a photodetector capable of collecting light radiation transmitted by the object, when the latter is illuminated by a light source, the optical properties of the object being then able to be modified following the capture of the analyte by the object. The source can then be included in said device.

Such a device is shown in FIG. 1, which comprises:

an object 1 in the form of a screw made according to the method of the invention, this object being made of a porous sol-gel material;

an enclosure 3 enclosing said object because the internal diameter of the enclosure corresponds to the diameter of the object, said enclosure being provided with:

an inlet 5 for the gas or the liquid to be analyzed, this gas or liquid being intended to traverse the helical structure of said object;

an outlet 7 for said gas or the liquid having traversed said helical structure;

an input 9 for the light source, which is arranged on the same side as the input 5; and

an output 11 for the light source for receiving the light after crossing the object.

The outgoing light is then analyzed for the detection or not of an analyte present in the gas or liquid that it is desired to analyze.

Other features and advantages of the invention will become apparent from the additional description which follows which relates to an example of preparation of a threaded object according to the method of the invention.

Of course, this additional description is only given as an illustration of the invention and does not in any way constitute a limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an optical detector comprising a screw-shaped object filling the waveguide function, this object being produced in accordance with the method of the invention. Figure 2 shows the different steps (respectively parts a) to i)) of the preparation of an object according to the method of the invention (Example 1).

Figure 3 shows a photograph in top view of the object obtained from Example 1 (right view) and its model (left view).

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

EXEM PLE 1

This example illustrates the preparation of an object from the method of the invention, this object being a screw having a diameter of 5 mm and a length of 10 mm and having a thread of 10 turns of screw per centimeter and a thread depth of 1 mm. a) Manufacture of the mold The threaded model used for the manufacture of the mold is illustrated by part a) of FIG. 2, which is a screw 13 having a diameter of 10 mm and a length of 20 mm.

The mold is prepared by the following succession of operations: 1-Preparation using a spatula of a mixture (20 g) of two components, respectively polydimethylsiloxane (PDMS) and a crosslinking agent according to a ratio of 10/1 (these components being available from Dow-Corning under the name SylGard 184);

2- Pouring of this mixture 15 into a plexiglass container 17 over a height of 5 mm thickness (part b) of Figure 2);

3- Vacuuming the whole set for 20 minutes by breaking the vacuum followed by baking at 70 ° C for 2 hours; 4- After cooking the mixture (thereby generating the crosslinking of the PDMS), placement of the threaded model 13 (having a diameter of 10 mm) on the resulting PDMS layer (part c) of Figure 2);

5. Preparation with a spatula of a mixture (30 g) of two components, respectively polydimethylsiloxane (PDMS) and a crosslinking agent at a ratio of 10/1 (these components being available from Dow Corning under the name of SylGard 184) followed by degassing under high vacuum (20 minutes by breaking the vacuum);

6. Pouring of the mixture 21 onto the threaded model 13 (placed on the layer of PDMS previously used) up to a height of 5 mm above the threaded model (part d) of FIG. 2);

7- Application of a high vacuum for 30 minutes to degass the assembly;

8- Heating the assembly at 70 ° C for 2 hours, so as to cause crosslinking of the polydimethylsiloxane, whereby a solid layer is formed around the model;

9- Manual demoulding of the mold plexiglass container 23 thus obtained (part e) of Figure 2);

10- Cutting the surplus of PDMS until a uniform mold thickness of 5 mm is obtained;

11- Opening the PDMS mold in two parts using a scalpel according to a dotted cutting plane 25 on part f) of Figure 2 to remove the starting threaded model 13 taken in the PDMS mold .

The two parts of the PDMS mold are then re-glued after plasma activation according to the following conditions:

The two parts of the mold are placed in a 0 ₂ plasma (Plasma 0 ₂ AST Product Inc), the following conditions being applied to activate the surface functions of the PDMS (PO ₂ 1 bar, Power 20 Watt, Duration 20 sec; Adaptation network 50-50%, Gas 120, Gas flow 60, Operating point 0.5); 2- After application of the plasma, the two surfaces of the mold to be bonded are brought into contact. Pressure is exerted to improve the contact between the two surfaces and thus improve the bonding;

3- The whole is put in the oven at 80 ° C for 4 hours.

The two parts of the mold are thus bonded, whereby a mold 27 is obtained having an internal cavity 29 corresponding to the shape of the object to be molded (part g) of FIG. 2). b) Manufacture of the sol-gel solution

The sol-gel solution is prepared by the following succession of operations:

1- Preparation of Solution 1: Mixture at room temperature with stirring of 4.66 ml (0.0208 mol) of tetraethylorthosilicate (78-10-4 Sigma-Aldrich) and 1.6 ml (0.068 mol) of water, to which 4 mL of anhydrous ethanol is added followed by 4 mL of 1M hydrochloric acid with stirring;

2- Putting the solution obtained in 1 in a pillbox hermetically sealed in an oven at 80 ° C for 4 hours for hydrolysis;

3- After 4 hours of hydrolysis, removal of solution 1 from the oven and cooling to room temperature;

4- Adding to the solution obtained in 3, 0.5 ml of a solution prepared by dissolving 30 μl of an ammonia solution in 5 ml of anhydrous ethanol, the resulting sol-gel solution to be injected into the mold just after this step. c) Manufacture of the object as such

The object is prepared according to the following sequence of operations:

1- Introduction of a needle 31 in the upper part of the mold to allow the evacuation of air, when the sol-gel solution will be injected (part h) of Figure 2);

2- 5 mL sample of the previously prepared sol-gel solution;

3- Insertion of the needle of the syringe 33 containing the sol-gel solution (which has just been taken) into the mold followed by a slow injection of the solution to avoid having a turbulent regime at the exit of the needle and prevent the formation of air bubbles on the walls of the mold (part h of Figure 2);

4- Removal of the needle 33 when the mold is filled with the sol-gel solution and removal of the needle 31 of air evacuation;

5- Resting the mold containing the sol-gel solution at room temperature for 1 hour until a gel is obtained;

Drying of the assembly in a rotary kiln (Agilent Technologies, model GA) at 70 ° C. for 7 days at a rotation speed less than one rotation per minute, whereby a hardened object 37 is obtained (part i ) of Figure 2) of smaller dimensions than those of the original model;

After drying, opening the two-part PDMS mold to remove the sol-gel monolith thus produced.

The object obtained has smaller dimensions than those of the original part (50% necking, hence a diameter of 5 mm), without this affecting the shape with respect to the original part.

Figure 3 shows a photograph in top view of the object obtained (right view entitled "sol-gel") and its model (left view entitled "master").

Claims

A method of manufacturing a molded article comprising at least one thread, said object being made of a hardened organic or inorganic material, said method comprising successively the following steps:

c) a step of drying within said mold of the object obtained in b), characterized in that said mold, at least during the implementation of step c), is a closed chamber, whose walls forming the boundary between the internal cavity and the outside of the mold are at least one material capable of allowing the evacuation of the gases from step c) and possibly from step b).

2. The method of claim 1, wherein the boundary walls between the inner cavity and the outside of the mold are of an elastomeric material.

3. Method according to claim 1 or 2, wherein the boundary walls between the inner cavity and the outside of the mold are made of a material of the family of polysiloxanes.

4. Method according to any one of the preceding claims, wherein the boundary walls between the inner cavity and the outside of the mold are made of a material of the polydimethylsiloxane family.

5. Method according to any one of the preceding claims, comprising, before step a), a step of preparing the mold of the object to be manufactured.

6. Method according to any one of the preceding claims, comprising, before step a), a step of preparing the curable liquid composition.

7. Method according to any one of the preceding claims, wherein the mold is a closed chamber for the implementation of step a) and / or step b).

8. Method according to any one of the preceding claims, wherein the object is an object capable of performing the function of waveguide.

The method of any one of the preceding claims, wherein the curable liquid composition is:

a polymerizable and / or crosslinkable organic composition, in which case the hardened organic material of the object is a polymeric organic material; or

a composition consisting of a sol-gel solution, in which case the hardened inorganic material of the object is a sol-gel material.

10. Device for capturing an analyte present in a fluid comprising:

an object made of a hardened organic or inorganic material capable of capturing said analyte, said object being produced by the method of the invention as defined according to any one of Claims 1 to 9;

a confinement element able to define a fluidic channel for the flow of said fluid along the object.

11. Device according to claim 10, which is an extractor or a detector of said analyte.