EP2076781A1

EP2076781A1 - Fluid flow device, assembly for determining at least one characteristic of a physicochemical system comprising such a device, corresponding determination process and screening process

Info

Publication number: EP2076781A1
Application number: EP07858431A
Authority: EP
Inventors: Mathieu Joanicot; Philippe Laval; Jean-Baptiste Salmon
Original assignee: Centre National de la Recherche Scientifique CNRS; Rhodia Operations SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Rhodia Operations SAS
Priority date: 2006-10-13
Filing date: 2007-10-12
Publication date: 2009-07-08
Also published as: FR2907228A1; WO2008046989A1; US20110032513A1; JP5261391B2; FR2907228B1; US8420397B2; JP2010506185A

Abstract

This device comprises: - a small plate (2), - at least one flow channel (20) cut into this small plate; - at least one storage channel (221-226) extending from this connection channel; and - a set of valves (V1-V6), each of which is suitable for allowing or stopping the flow of fluid in a corresponding storage channel.

Description

FLUID FLOW DEVICE, ASSEMBLY FOR DETERMINING AT LEAST ONE CHARACTERISTIC OF A PHYSICO-CHEMICAL SYSTEM COMPRISING SUCH A DEVICE, METHOD OF

DETERMINATION AND CORRESPONDING SCREENING METHOD

The present invention relates to a fluid flow device, a set of determination of at least one characteristic of a physico-chemical system comprising such a device, a determination method implementing this set, as well as a screening method. corresponding.

Within the meaning of the invention, a physicochemical system, which is intended to determine at least one characteristic, may be a pure body, but also a compound, such as for example one or more solute (s) dissolved in a solvent or a mixture of several pure bodies. Within the meaning of the invention, a characteristic of this physico-chemical system is in particular a characteristic curve of such a system, in particular a thermodynamic limit, in particular a phase diagram, such as a solubility curve, or even the miscibility limit for a mixture of two liquids.

The present invention aims more particularly, but not exclusively, the study of the solubility of such a physicochemical system. It is recalled that the solubility of a solute in a solvent is the maximum concentration of this solute that can be dissolved in this solvent at a given temperature. The solubility curve of this solute, which therefore forms a physicochemical system according to the invention, corresponds to the variation of this solubility as a function of temperature.

The methods conventionally used to determine this solubility curve are various. They involve different measures, during which at least one parameter is changed, especially the solute concentration and / or the temperature. In general, the methods used in the state of the art are of a systematic nature, so that they prove to be particularly lengthy to implement.

Under these conditions, the invention proposes to remedy this drawback. It aims in particular to provide a solution for reliably determining at least one characteristic of a physicochemical system, which is accompanied by a significantly reduced handling time compared to the prior art.

For this purpose, it relates to a fluid flow device according to claim 1 attached.

Other advantageous features of this device are the subject of appended claims 2 to 12.

The invention also relates to a set of determination of at least one characteristic of a physico-chemical system according to claim 13 attached. The invention also relates to a method for determining at least one characteristic of a physico-chemical system according to claim 14 attached.

Other advantageous features of this process are the subject of the appended claims 15 to 29. The invention finally relates to a screening method according to the appended claim 30.

The invention will be described below, with reference to the accompanying drawings, given solely by way of non-limiting example, in which: - Figure 1 is a front view, schematically illustrating a set of determination according to 1; invention, FIGS. 2A and 2B are side views, illustrating two positions of a valve fitted to the determination assembly of FIG. 1;

FIG. 3 is a graph illustrating a solubility curve that the invention proposes to determine;

FIGS. 4A to 4C are front views, similar to FIG. 1, illustrating various steps of implementation of the determination method according to the invention;

FIG. 5 is a view on a larger scale of FIG. 4; and

- Figure 6 is a graph, similar to Figure 3, on which is reported a curve obtained according to the invention.

FIG. 1 illustrates a determination assembly according to the invention, which firstly comprises a fluid flow device, designated as a whole by reference numeral 1. This latter comprises a wafer 2, which is produced in a known manner in FIG. for example PDMS (poly (dimethylsiloxane)). However, as an alternative, it may be provided to form it in any other suitable material, such as glass, silicon, PMMA (polymethyl methacrylate), or a photoresist of SU-8 type MicroChem company, or NOA type from Nordland.

This wafer 2 has a length and a typical width of between 5 and 10 cm, and a typical thickness of 5 mm. It is etched with different microchannels, according to the conventional procedures of the state of the art, which are described in particular in "D. C DUFFY, J. C. McDONALD, Olivier J. SCHUELLER, George M. WHITESIDES, ANAL. CHEN, 70, p.4974-4984, 1998. " In the example illustrated, the characteristic section of these microchannels is typically between 100 μm ²

(for example 10 μm by 10 μm) and 1 mm ² (for example 1 mm by

1 mm). Typically, this dimension causes a laminar flow within these microchannels, with a Reynolds number of less than 10. As an indication, in order to illustrate the properties of these microchannels, mention will be made of the work of Stéphane COLIN, microfluidic (treated

EGEM microsystems series, published by HERMES SCIENCES PUBLICATION).

However, it will be noted that, by way of an alternative, the invention also finds application in millifluidic flow channels, ie whose cross-section is greater than the values mentioned above. Thus, the cross section of these millifluidic channels may reach a value close to 9 mm ² , for example 3 mm by 3 mm, or even close to 25 mm ² , for example 5 mm by 5 mm.

FIG. 1 illustrates more particularly the design of the microchannels, which are etched on the wafer 2. There are firstly two microchannels 4 and 6 for supplying two first components, which are associated with two inputs 8 and 10. the latter is adapted to receive a first end of a nonrepresented tube, the other end is connected to a syringe also not shown. In a conventional manner, the flow rate of the component administered by each syringe is controlled by means of a syringe pump, also not shown. There is further provided a microchannel 12, associated with an inlet 14 which cooperates with a tube, with a syringe, and with a not shown syringe driver. This microchannel 12 is divided into two branches 16, affecting approximately a square shape, which meet at an intersection 18. A microchannel 19 mixing, in which open the downstream ends of the two microchannels 4 and 6, is put in communication with this intersection 18. Downstream of the intersection 18, namely below this in Figure 1, a so-called connecting channel 20 extends longitudinally, in this case vertically. This connecting channel 20 is provided with an output 20 ', which will be noted that it is optional. It is put in communication with several so-called storage channels 22χ to 22β. For the purposes of the invention, the term "several" means "at least two".

In the illustrated example, these storage microchannels extend horizontally, namely that they are parallel to each other, while being perpendicular to the connecting channel 20. However, it can be expected that these storage channels are not perpendicular to the link channel and are not parallel to each other. Thus, it is possible to arrange them around a circle. As shown in Figure 1, the connecting channel 20 and the various storage channels 22i 22 ₆ define a comb, whose base is formed by the connecting channel and the teeth are formed by the storage channels. By analogy with electricity, the different storage channels thus extend in parallel from this link channel.

It may further be noted that this link channel and these storage channels define a quadrilateral, one side of which is formed by the link channel 20, two additional sides are defined by the end storage channels 22χ and 22ε, and one The last side is defined by a segment parallel to the link channel 20, which connects the downstream outputs of the different storage channels. In the illustrated example, the aforementioned quadrilateral is a rectangle.

In the illustrated example, the storage microchannels 22i to 22ε are represented in number of six. However, in practice, a number of these channels is advantageously used which is between two and fifteen, preferably between five and ten. One can also consider using a single microchannel storage.

At their downstream end, situated on the right in FIG. 1, the storage microchannels cooperate with valves V ₁ to V ₆ , illustrated in a schematic manner, one of which V ₁ is shown more precisely in FIGS. 2A and 2B. The outlet 22 'x of the microchannel 22χ is placed in communication with a rigid tube 24, made for example of ethylene-propylene fluorinate (Teflon FEP) or Polyetheretherketone (PEEK ^® ), namely that it does not deform substantially radially. during the flow of a fluid. Then, this rigid tube 24 opens into a flexible tube 26, made for example of PVC or silicone, which is associated with the valve Vi. The latter is a tube-clamping solenoid valve of a type known per se.

It should be noted that the tubes 24 and 26 form a connecting member, connecting the outlet 22 'i of the microchannel 22i with the valve Vi. This connecting member is independent of the wafer, namely that it can be reported, including removably, on the walls of the aforementioned outlet. This is advantageous, insofar as it is possible to make the wafer 2 of any material, regardless of the nature of the valve and its connecting member.

This solenoid valve Vi is conventionally provided with a piston 28 adapted to be actuated by a not shown coil, capable of crushing the tube 26 against a support 30. It should be noted that the length 1 of the flexible tube 26, between its connection with the rigid tube 24 and the pinching zone by the piston 28, is very small, for example close to 2 mm. This makes it possible to limit the parasitic displacements of the fluid in the different channels during the maneuvers of the valve.

The structure of the valve shown in Figures 2A and 2B is advantageous. Indeed, this valve is physically isolated, thanks to the presence of the flexible tube 26, relative to the fluid present in the microchannel storage. Furthermore, this valve is reliable, while having a relatively low cost.

As will become more clearly apparent from the following, the invention provides for imposing two gradients according to the two dimensions x and y, respectively defined by the storage microchannels 22 and the connecting microchannel 20. In this case, according to FIG. direction x, it is in particular to impose a gradient of operating condition, including temperature, humidity, illumination, or concentration of another compound.

Under these conditions, the entire determination according to the invention comprises means for imposing such a gradient along the channels 22. In the example illustrated, these means comprise two Peltier modules 32i and 32 ₂ for d impose a temperature gradient. In a manner known per se, a Peltier effect module is capable of causing temperature variations as a function of an electric current imposed on it. For purely non-limiting reasons, it is possible to use modules conforming to those marketed by Melcor under the reference CPI 4-71-06L.

The first 32i of these modules is placed in the vicinity of the upstream end of the storage microchannels 22, illustrated on the left of FIG. 1. Moreover, the second 32 ₂ of these modules is provided near the downstream end of these same channels, namely that to the right of this figure, where these two modules are shown in phantom. As will be seen more precisely in what follows, each of these modules 32χ and 32 ₂ may constitute a hot source or a cold source, .according to the steps of the method according to the invention.

Finally, the determination unit is provided with means capable of analyzing the contents of the different microchannels formed in the wafer 2. In the example illustrated, these are means of visual analysis, namely a microscope 34 shown The microscope 34, which is associated with an unrepresented camera, is connected in a conventional manner to a processing computer 36.

The implementation of the determination set according to the invention, described above, will now be explained in the following. In the example, it is desired to determine the solubility curve of a solute in a solvent, such as that shown in FIG. 3. On the latter, the ordinates correspond to the solute concentration C in the solvent, whereas the temperature T is plotted on the abscissa. Thus, below and to the right of this solubility curve CS, the solute is entirely liquid whereas, at the top left of this same curve, crystals of this solute can form in the solution.

For the purposes of the invention, this solute A constitutes a physicochemical system that the invention proposes to study, which can be introduced into the microchannel 4. Furthermore, the abovementioned solvent B can be admitted via the microchannel 6, so that the mixture of the solute and the solvent forms a physicochemical set within the meaning of the invention. Finally, a carrier phase P, such as oil, which is not miscible with the solute mixture ^• and solvent, is admitted by the microchannel 12.

In a preliminary step, it is a question of filling the various microchannels 20 and 22, as well as the tubes 24 and 26, by means of oil or of any appropriate liquid, which makes it possible to overcome the problems due to the compressibility of the air. The different valves Vi to V ₆ are also closed. Then, only the first valve V ₁ (FIG. 4A) is opened, while admitting solute A and solvent B via microchannels 4 and 6, as well as oil via microchannel 12.

As shown in FIG. 4A, downstream of the intersection 18, a succession of drops Gi, which are directed towards the first storage channel 22i, is formed in a manner known per se. Each drop is formed by the mixture of solute A and solvent B, namely the physicochemical set defined above. In the usual way, these drops Gi are separated from each other by sections of oil, forming a carrier phase P immiscible with these drops. It will be noted that, during this step, a sufficiently high temperature is imposed so that the solute is entirely in liquid form in the drops Gi, that is, at the bottom and to the right of the curve CS of the figure 3.

The values of the respective flow rates of solute and solvent, admitted via channels 4 and 6, make it possible to know the concentration Ci of solute in the different drops Gi. In this respect, the sum of the flow rates of the solute and the solvent is between 0.1 mL / hr and 5 mL / hr, in particular between 0.5 and 1 mL / hr. The oil flow admitted by the microchannel 12 is between 0.5 and 10 mL / hr, especially between 1 and 5 mL / hr. Once the first microchannel 22i is filled with first drops Gi, it closes the first valve Vi, according to the procedure explained in Figure 2B, while opening the second valve V ₂ (Figure 4B), according to the procedure of Figure 2A . Moreover, the respective flow rates of solute and solvent are modified so as to form drops G ₂ in which the solute concentration C2 is different from that mentioned above.

This then makes it possible to fill the second storage microchannel 22 ₂ _. by means of a second type of drops G ₂ , as shown in Figure 4B. Iteratively, the different microchannels 22i to 22e are filled by means of different drops Gi to Ge, for which the solute concentrations vary from Ci to Ce. It is advantageous for this concentration to vary along the y axis in the various microchannels. 22. This concentration can thus vary determinably with the ordinates of the microchannels, especially monotonically, for example linearly, exponentially, or logarithmically.

At the end of these different steps (see FIG. 4C), all the storage microchannels 22 ±, where i = 1 to 6, were filled by means of drops G 1. Moreover, for the same microchannel 22i, the concentration C 1 of solute in the set of drops G 1 is identical while, in the different channels 22 ₁ to 22 ₆ , the concentrations C 1 to C ₆ are different.

As mentioned above, the filling of the various microchannels 22 has been performed at a high temperature, so that the different drops Gi to G ₆ are in the fully liquid state. Then it is a question of lowering the temperature prevailing in these microchannels 22, so as to move towards the part situated at the top left of the curve C of FIG. 3, and so as to crystallize the solute present in all of these drops. This change in temperature is obtained by modifying, as appropriate, the electric current supplied to the Peltier modules 32 ₂ and 32 _2. Next, it is a matter of imposing a temperature gradient along the various storage channels 22 ₁ to 22. . For this purpose, the left Peltier module 32 _X is controlled so as to generate a relatively low temperature on its surface, for example around 10 ⁰ C, while the right module 322 is controlled so as to generate a relatively high temperature for example of the order of 60 ^° C. Given the nature of the wafer 2, the application of these different temperatures leads to a substantially linear gradient along each microchannel 22. Thus, at the upstream end, the temperature is close to that imposed by the module 32i while at the downstream end, the temperature is close to that imposed by the module 322-

The fact of filling the various microchannels 22 ₁ to 22 ₆ with different physicochemical assemblies makes it possible to vary the concentration of solute along the y axis. Furthermore, the implementation of Peltier 32χ, 32 ₂ modules makes it possible to continuously vary the temperature along the x axis. In accordance with the invention, an orthogonal reference mark similar to that of the graph represented in FIG. 3 has thus been recreated, as illustrated in FIG. 5, where the concentration values Ci to Cc are plotted on the y-axis.

It is then necessary to carry out an analysis step, so as to identify the drops of storage microchannels 22 where crystals are present. This analysis is conducted visually through the microscope 34. Advantageously, this microscope 34 has a wide field of view, to observe at the same time time the entire wafer. This is for example a binocular microscope.

By way of example, an observation can be made through a crossed analyzer and polarizer to easily detect the presence of crystals that are birefringent. If the crystals are large enough, it is possible not to use birefringence.

For each microchannel of storage, namely for i = 1 to 6, we note in Figure 5 Gi 'the drops in which are present crystals and Gi' 'drops that are lacking. For the same storage channel, the drops with crystals are located on the left, namely on the side of the lowest temperature.

For each i of 1 to 6, Gi (1) and Gi (1) respectively denote the two adjacent drops having different states, one of which is crystallized and the other of which is not crystallized. In other words, the drop Gi '(1) is the drop having the highest temperature among all those crystallized, while the drop Gi''(1) is the drop with the lowest temperature among all those not crystallized. We then deduce two temperatures, respectively noted T ₁ 'and Ti'', which correspond to the drops thus identified.

We then deduce the solubility temperature Ti, for each concentration Ci, where i = 1 to 6:

Ti = (Ti '+ T ₁ ") / 2.

The computer 36 then places, on the graph of FIG. 6, the different values Ti to Tβ thus obtained for the concentrations Ci to C ₆ . From these different points, we thus obtain a solubility curve CS ', represented in FIG. 6, which is close to that CS of FIG.

In the example described above, the solubility curve a. been plotted from six points, corresponding to six microchannels of storage. It will be understood that, if it is desired to improve the accuracy of the method of the invention, it is a question of increasing the number of microchannels of storage, which will make it possible to correspondingly increase the number of points from which performed the solubility curve. It is also possible to increase the number of drops present in the same storage channel, which contributes to reducing the distance between two adjacent drops. This improves the accuracy of the solubility temperature.

At the end of the implementation of the steps described above, it was possible to determine a characteristic of the physico-chemical system to be studied, namely its solubility curve. It is then possible to repeat this sequence of steps with another physico-chemical system, while associating it with the same solvent and keeping the same concentrations and the same temperature gradient. Iteratively, these steps are carried out for a whole range of physico-chemical systems so that, at the end of the screening method thus implemented, one can then identify at least one physicochemical system of interest depending on the application. referred.

The invention is not limited to the example described and shown. Thus, in this example, the concentration of the solute varies along the y-axis, ie for different channels. However, another parameter of the physico-chemical system that the invention proposes to study can be varied. Thus, it is possible to admit, via the microchannel 4, a first fluid comprising a solute and a first type of solvent and, via the microchannel 6, a second fluid formed from this same solute and a second solvent miscible with the first solvent. . By adjusting injected flow rates in these microchannels, the storage channels are filled by means of a physicochemical unit, for which the concentration of solute is constant but the proportion of the two aforementioned solvents is variable. As a further variant, it is also possible to vary, along the y axis, the percentage of impurities present in the physicochemical assembly consisting of the solute and the solvent. In this case, a solution is injected at a given concentration of solute in the channel 4. Moreover, in the channel 6, the same solution is injected, which additionally comprises a given concentration of impurities, such as nanoparticles or molecules. Thus, according to the ratio of flow rates, the concentration of impurities in the drops tends to vary.

As a further example, it is possible to study diagrams of liquid-liquid equilibrium phases, for example ethanol-hexadecane. According to the y axis, the proportion of one liquid is varied with respect to the other and a temperature gradient is imposed along the x axis. A limit is then observed between homogeneous drops and drops consisting of two immiscible liquids.

In the example taken and shown, the temperature was varied along the different storage channels, namely along the x axis. However, it is possible to vary another operating condition, such as the hygrometric degree, the illumination or the concentration variation of another compound. In the example described and shown, the analysis is of a visual type, thanks to the use of the microscope 34. However, as a variant, other types of analysis may be provided, especially of the Rarαan spectroscopy type, spectroscopy. infrared, UV or visible spectroscopy. As a further variant, it is possible to probe each drop by means of an analysis apparatus, for example of the RAMAN spectroscope type. This can be done automatically, by placing the wafer on a table (x, y) motorized and programmable, known type, so as to successively place each drop next to the analysis apparatus.

In the example described and shown, there are identified drops having two different states, namely a crystallized state and a non-crystallized state. However, these different states, identified according to the invention, may be of another type, namely for example a simple liquid state on the one hand, and the presence of two immiscible liquids on the other hand. It is thus possible to access a characteristic curve different from a solubility curve, namely the miscibility limit in the case of liquid-liquid equilibria.

As a further alternative, it is also possible to perform a two-dimensional mapping of a chemical reaction. Reagents at different concentrations are introduced into the microchannels of storage, while the temperature or illumination is varied along the x axis. The product of the corresponding reaction is then observed, for example by Raman spectroscopy.

In the example described and shown, a succession of drops, forming plugs, are directed in the different microchannels of storage. However, it is possible to directly inject a mixture of solute and solvent, without using a carrier phase.

The invention achieves the previously mentioned objectives.

Indeed, the filling operations of the various storage channels, made according to the invention, are reveal significantly faster than successive manipulations, which should be carried out in the state of the art. Furthermore, it is possible, thanks to the invention, to perform a direct reading of the desired characteristic, including a simple visual analysis.

In addition, the possibility of forming, thanks to the invention, drops of particularly small volume, is advantageous .. Indeed these drops are real microreactors which, given their scale, are homogeneous and therefore do not require agitation, as might be the case for macroscopic systems. This size of drops also ensures a rapid thermal equilibrium. Moreover, the use of this microscopic scale makes it possible to limit the inadvertent presence of impurities, which confers great precision on the determination thus made.

Finally, it will be noted that the use of plugs is advantageous in terms of the accuracy of the determination of the desired characteristic. Indeed, the various plugs present in the storage channels are individual entities, likely to retain their original properties, especially their initial concentration.

Claims

Fluidic Flow Device, comprising:

- a wafer (2), - at least one connecting channel (20) formed in this wafer; a plurality of storage channels (22i ~ 22 ₆₎ extending from this connecting channel; a plurality of valves (Vi-V ₆ ), each of which is adapted to allow or stop the flow of fluid in a corresponding storage channel; and means (32χ, 32 ₂ ) for imposing a gradient of at least one condition along each storage channel (22 _x -22 ₆ ).

2. Fluidic flow device according to claim 1, characterized in that this device further comprises means (4, 6, 12, 18) for forming a succession of plugs (Gi-Ge) in a carrier phase ( P), in the connecting channel (20) and each storage channel (22).

3. fluid flow device according to claim 2, characterized in that the plug forming means comprise at least a first supply channel (4, 6) of the component (s) of said plugs, and a second supply channel (12) of the carrier phase, forming an intersection with the or each first supply channel.

4. Fluid flow device according to any one of the preceding claims, characterized in that the cross section of the connecting channel (20) and each storage channel (22 _x -22 ₆ ) is between 100 microns and ² 25 mm ² .

Fluidic flow device according to claim 4, characterized in that the connecting channel and each storage channel are microchannels (20, 22 22χ- _6), whose cross section is between 100 microns ² and 1 mm ^2.

6. Fluid flow device according to any one of the preceding claims, characterized in that each valve (V ₁ -V ₆ ) is of the tube clamp type.

7. Fluidic flow device according to any one of the preceding claims, characterized in that the outlet (22 'i) of each storage channel (22 _X - 22 ₆ ) is placed in communication with a corresponding valve (Vi- V ₆ ) via a connecting member (24, 26) independent of the wafer (2).

8. Fluidic flow device according to claim 6 and 7, characterized in that the end of each storage channel (22i-22 ₆ ) opposite the connecting channel - (20) is placed in communication with a rigid tube ( 24), which opens into a flexible tube (26) adapted to cooperate with a corresponding valve (Vi-Vβ) pinching tube.

9. fluid flow device according to one of the preceding claims, characterized in that the storage channels (22 _! -22 ₆ ) are parallel to each other.

10. Fluidic flow device according to claim 9, characterized in that the parallel storage channels (22i-22s) are perpendicular to the connecting channel (20).

11. Fluid flow device according to any one of the preceding claims, characterized in that it is provided between two and fifteen, preferably between five and ten storage channels (22! -22 ₆ ).

12. Fluidic flow device according to the preceding claim, characterized in that the means for imposing a gradient comprise a first source (32χ), placed in the vicinity of a first end of each storage channel, and a second source

(322), placed in the vicinity of a second end of each storage channel, the first and second sources being adapted to impose different conditions, in particular different temperatures.

13. An assembly for determining at least one characteristic of a physicochemical system, comprising a fluid flow device according to any one of the preceding claims, means of analysis (34) suitable for identifying at least one two different states of the physicochemical system, or a physico-chemical unit comprising said physico-chemical system, in each storage channel, as well as processing means (36) related to the analysis means (34). ).

A method for determining at least one characteristic of a physico-chemical system, implementing a determination set according to claim 13, wherein

different fractions of said physicochemical system (A) are injected into the different storage channels

(22χ-22 ₆ ), by varying at least one parameter of this physico-chemical system (A) or of a physico-chemical unit (Gi-Gβ) comprising this physicochemical system, in the different channels, while now this invariant parameter in the same storage channel;

said fractions of the physicochemical system are immobilized; - we impose a gradient of at least one condition along the different storage channels (22i-22 _6);

at least two different states of the physico-chemical system, or of said physicochemical set (Gx-Gβ), are identified in the storage channels; and - We deduce the or each characteristic of this physico-chemical system.

15. Determination method according to claim

14, characterized in that the parameter that is varied is the composition of the physico-chemical system or the physico-chemical complex comprising this system.

16. Determination method according to the claim

15, characterized in that the parameter that is varied is the concentration of the physico-chemical system in the physico-chemical complex.

17. Determination method according to claim 14, characterized in that the physico-chemical unit is formed by the mixture of the physicochemical system, which is in particular a solute, and an adjuvant, in particular a solvent, and the parameter that one varies is the nature of the adjuvant, while maintaining the same concentration in physicochemical system in the physicochemical set.

18. Determination method according to any one of claims 14 to 17, characterized in that the parameter of the system or of the physicochemical unit is varied proportionally, in particular linear, with respect to the distance separating the different channels. storage (22χ-22 ₆ ).

19. Determination method according to one of claims 14 to 18, characterized in that the condition which is imposed a gradient is an operating condition, including the temperature, the hygrometric degree or the intensity of illumination.

20. Determination method according to one of claims 14 to 19, characterized in that the two different states correspond to different phases of the system and / or the physicochemical set.

21. Determination method according to claim 20, characterized in that the different phases correspond respectively to the presence and absence, in the physicochemical set, of crystals formed by the physicochemical system.

22. Determination method according to one of claims 14 to 21, characterized in that the system and / or the physicochemical set is injected in the form of plugs, in particular drops (Gi-G ₆ ), into a carrier phase (P) immiscible with these plugs.

23. Determination method according to one of claims 14 to 22, characterized in that injects the physico-chemical system with a first value of the parameter in a first storage channel (22i), while keeping open a first valve (Vi) associated with this channel and keeping the other valves closed (V ₂ -V ₅ ), then closing said first valve while opening a second valve (V ₂ ), and injecting the physicochemical system with a second value of parameter in the second storage channel (22 ₂ ), then iteratively injects the physicochemical system with other values of said parameter in the other storage channels.

24. Determination method according to one of claims 14 to 23, characterized in that fills the various storage channels (22i ~ 22 ₆ ) with a physicochemical system and / or a physicochemical set in a first state, in particular liquid, this system and / or this set is brought into a second state, in particular crystallized, and said condition gradient is applied, so as to bring back to the first initial state only a part of the system and / or all.

25. Determination method according to one of claims 14 to 24, characterized in that said at least two different states are identified by analysis of the different fractions of the physico-chemical system injected into the storage channels.

26. A method of determination according to claim 25, characterized in that a visual analysis is carried out, in particular by means of a microscope (34) associated with a camera.

27. Determination method according to claim 25, characterized in that a spectroscopy-type analysis is carried out, in particular RAMAN or infrared.

28. A method of determination according to any one of claims 22 to 27, characterized in that, for each storage channel (22i-22g), two adjacent values are identified (T'i (1), T''i ( l)) of the parameter which correspond to two different states of the plugs (G ₁ -G ₆ ) and an average of these two values is obtained to access a characteristic value (Ti) of this parameter, for each storage channel.

29. Determination method according to claim 28, characterized in that the characteristic of the physicochemical system is a characteristic curve of this system, and this characteristic curve is deduced from the different characteristic values (Ti-Tg).

30. A method for screening several physicochemical systems, in which several physico-chemical systems are prepared, determining at least one characteristic of each physicochemical system according to any one of claims 14 to 29 and identifying at least one physicochemical system. preferred chemistry having at least one preferred characteristic.