ASSEMBLY FOR PRESSURE CONTROLLED FLUID RELEASE AND ITS METHOD THEREFORE

Abstract

The invention relates to an assembly for contactless pressure-controlled release of a fluid comprising a non-compressible compartment, at least two fluids in fluidic contact and enclosed inside the non-compressible compartment, one of the two fluids being compressible, and one channel for fluid flow.

Claims

1. An assembly comprising: a gas and a fluid, the fluid having a density greater than a density of the gas, a non-compressible compartment, the gas and the fluid being in fluidic contact and enclosed inside the non-compressible compartment, and a microfluidic channel for fluid flow, wherein the channel comprises a first end connected to a side of the non-compressible compartment and a second end which is free, wherein the microfluidic channel has a Bond number Δρ×g×s2/σ strictly less than 1, wherein: Δρ is a difference in kg/m.sup.3 of a density of the gas and a density of the fluid, S.sub.2 is a section of the microfluidic channel in m.sup.2, g is the gravitational acceleration, and σ a is a surface tension in N/m between the gas and the fluid.

2. The assembly of claim 1, wherein the non-compressible compartment is a macrofluidic reservoir having a Bond number $\frac{\Delta \rho \times g\times S1}{\sigma }$ strictly greater than 1, wherein S.sub.1 is a section of the non-compressible compartment in m.sup.2.

3. The assembly of claim 2, wherein the section of the non-compressible compartment is greater than 10 mm.sup.2.

4. The assembly of claim 1, wherein the gas is air.

5. The assembly of claim 1, wherein the fluid is a liquid.

6. The assembly of claim 1, wherein the non-compressible compartment comprises a cap and a fluid receiving vessel, wherein the cap comprises a base and a lateral wall external surface and the fluid receiving vessel comprises the microfluidic channel and a lateral wall internal surface, the cap being fitted to the fluid receiving vessel such that the lateral wall external surface of the cap and the lateral wall internal surface of the fluid receiving vessel form a fluid tight seal.

7. The assembly of claim 6, wherein the base of the cap has a flat external surface so as to be stable on a horizontal surface for easy filling of the fluid.

8. A device comprising at least one array of assemblies according to claim 1, said assemblies being linked to one another by connecting means.

9. The device of claim 8 comprising a plurality of parallel arrays of assemblies, said parallel arrays of assemblies being linked together by at least one connecting bridge.

10. The device of claim 8, further comprising a seal on the microchannel to prevent the fluid from escaping before pressure control.

11. An apparatus comprising the assembly of claim 1, further comprising a pressure controller provide to provide the gas enclosed in the non-compressible compartment with a predetermined pressure so as to release the fluid through the microchannel from a fluid receiving vessel to a well.

12. A method for forming the assembly of claim 6 comprising the following steps: filling the cap with the fluid, fitting said cap with the fluid receiving vessel, so that the lateral wall external surface of the cap and the lateral wall internal surface of the fluid receiving vessel form a fluid tight seal.

13. A method comprising the steps of: setting the assembly (A) of claim 6 into an apparatus comprising a pressure controller in a configuration where the cap is on top of the receiving vessel, and implementing a pressure cycle so as to release the fluid from the fluid receiving vessel to a well.

14. The method of claim 13, wherein the pressure cycle comprises the following steps: increasing a pressure by at least 20 mbar from atmospheric pressure for gas inlet into the non-compressible compartment; and then decreasing by the back to initial atmospheric pressure for gas expansion so as to release fluid from the fluid receiving vessel to a well.

15. The method of claim 13, wherein the pressure cycle comprises the following steps: decreasing a pressure by at least 20 mbar from atmospheric pressure for fluid aspiration from the fluid receiving vessel to a well, and then increasing the pressure increase back to initial atmospheric pressure.

16. The assembly of claim 1, wherein the section of the microfluidic channel is less than 1 mm.sup.2.

17. The assembly of claim 1, wherein the fluid is an oil.

18. An apparatus comprising the assembly of claim 8, further comprising a pressure controller provide to provide the gas enclosed in the non-compressible compartment with a predetermined pressure so as to release the fluid through the microchannel from a fluid receiving vessel to a well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0084] FIG. 1 is a schematic representation of the assembly according to the invention.

[0085] FIG. 2 is a perspective view of an array of caps for an embodiment of assembly according to the invention.

[0086] FIG. 3 is a cross sectional view of an array of assemblies according to the invention.

[0087] FIG. 4 is a perspective cross sectional view of an array of assemblies according to the invention.

[0088] FIG. 5 is a top view of an array of parallel fluid receiving vessels.

[0089] FIG. 6 is a top view of an array of parallel fluid receiving vessels one array being an assembly according to the invention.

[0090] FIG. 7 is a top view of an array of parallel loading wells.

[0091] FIG. 8 is a perspective view of the assembly according to the invention operatively coupled with a microfluidic chip.

[0092] FIG. 9 is a perspective cut view along the line AA of FIG. 8 with the loading well on top of a microfluidic chip shown for clarity.

[0093] FIG. 10 illustrates the process steps according to an embodiment of the invention.

[0094] FIG. 11 illustrates process steps according to an embodiment of the invention for fluid release.

[0095] FIG. 12 illustrates process steps according to another embodiment of the invention for fluid release.

DETAILED DESCRIPTION

[0096] The following detailed description will be better understood when read in conjunction with the drawings. For the purpose of illustrating, the assembly is shown in the preferred embodiments. It should be understood, however that the application is not limited to the precise arrangements, structures, features, embodiments, and aspect shown. The drawings are not drawn to scale and are not intended to limit the scope of the claims to the embodiments depicted. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims.

[0097] As shown in FIG. 1, this invention relates to an assembly A for contactless pressure-controlled release of a fluid 3 comprising a non-compressible fluid compartment 1. This compartment is actually non-compressible and configured to contain fluids. By non-compressible, it is meant that its volume does not change under a variation of outside pressure of 1 atm of more than the volume of one droplet of fluid 3 to be delivered through surface 20a. In other words, when outside pressure increases of 1 atm, mechanical deformation of the compartment is negligible as compared to the volume of a droplet of fluid 3 to be delivered through surface 20a. It will be designated as non-compressible compartment thereafter. At least two fluids 3 and 4 in fluidic contact are enclosed inside the non-compressible compartment 1, one of the two fluids: 4, being a gas and wherein the fluid 3 to be released has a density superior to the gas 4. Said non-compressible compartment 1 is connected to one channel 20 for fluid flow. The channel 20 extends outward said non-compressible compartment on side 20a and has a free end at the other side 20b.

[0098] With this assembly, pressure inside the non-compressible compartment can be adjusted by external pressure, without connection to a pressure source via a channel. Indeed, ambient gas may be introduced in the non-compressible compartment through the channel and fluid 3, thus increasing pressure within the non-compressible compartment. Reversely, gas 4 contained in the non-compressible compartment may expand if external pressure is lowered, thus forcing fluid 3 out of the non-compressible compartment. Finally, fluid 3 delivery from assembly is controlled by ambient gas pressure, without requiring any connector with the non-compressible compartment and fluid 3 is delivered—just dripping—on any device or chip below the non-compressible compartment, without requiring a specific connector. This mode of operation is referred to as contactless.

[0099] The channel 20 is unable to allow a simultaneous double flow. It has section S2 in m.sup.2 and a Bond number

[00005]$\frac{\Delta \rho \times g\times S2}{\sigma }$

strictly lower than 1, where: [0100] Δρ is the difference in kg/m.sup.3 of the densities between the gas 4 and the fluid 3 to be released, [0101] g is the gravitational acceleration which value is 9.80665 m/s.sup.2, [0102] σ is the surface tension in N/m between the gas 4 and the fluid 3 to be released.

[0103] In such a configuration, the fluid 3 to be released in a controlled manner does not flow through the channel 20 under gravitational forces only. Fluid 3 is trapped within the compartment 1 with gas 4 on top.

[0104] The section S2 of the channel 20 is of course preferably constant, however, if it is not the case and the section evolves as in a cone, it should be taken the lowest section of the channel 20. Preferably, the channel 20 has a hollow cylindrical shape. The section S2 to take into account is the internal one through which the fluid will flow in a controlled manner under pressure. Usually, section S2 of the channel 20 is less than 1 mm.sup.2.

[0105] As to the non-compressible compartment 1, it has a rectangular shape but can have any other shape as long as the compartment itself is not compressible. The non-compressible compartment 1 is a macrofluidic reservoir with a section S1 in m.sup.2 and a Bond number

[00006]$\frac{\Delta \rho \times g\times S1}{\sigma }$

strictly greater than 1, where: [0106] Δρ is the difference in kg/m.sup.3 of the densities between the gas 4 and the fluid 3 to be released, [0107] g is the gravitational acceleration which value is 9.80665 m/s.sup.2, [0108] σ is the surface tension in N/m between the gas 4 and the fluid 3 to be released.

[0109] The section S1 of the non-compressible compartment 1 is of course preferably constant, however, if it is not the case and the section evolves as in a cone or an amphora, it should be taken the lowest section of the non-compressible compartment 1. Preferably, the non-compressible compartment 1 has a hollow cylindrical shape. The section S1 to take into account is the internal one through which the fluid will flow. Usually, section S1 of the non-compressible compartment 1 is greater than 10 mm.sup.2.

[0110] In an embodiment, the fluid 3 to be released is a solution, i.e. it does not contain any dispersed solid particles.

[0111] In an embodiment, fluid 3 to be released is non-volatile, which means here that boiling point under pressure of 1 atm is greater than 80° C. Boiling point under pressure of 1 atm is preferably greater than 100° C., more preferably greater than 150° C., even more preferably greater than 150° C. Fluids 3 having boiling point under pressure of 1 atm greater than 200° C. or 250° C. are especially preferred.

[0112] In particular, fluid 3 is a single pure liquid, such as perfluoro-hexane, perfluoro-cyclohexane, perfluoro-decaline, perfluoro-perhydrophenantrene, poly-hexafluoropropylene oxide (such as poly-hexafluoropropylene oxide with carboxylic end group), perfluoro polytrimethylene ether, poly perfluoroalkylene oxide, fluorinated amines (such as N-bis(perfluorobutyl)-N-trifluoromethylamine, tri(perfluoropentyl)amine, mixture of perfluorooctane amine and perfluoro-1-oxacyclooctane amine, or perfluorotripropylamine), fluorinated ethers (such as mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether), 3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl)-hexane, or 2,3,3,4,4-pentafluorotetrahydro-5-methoxy-2,5-bis[1,2,2,2-tetrafluoro-1-trifluoromethyl) ethyl]-furan. In this embodiment, assembly is suitable to release a fluid on any device and prevent evaporation of liquids already contained in said device.

[0113] Thanks to this design a precise pressure-controlled fluid release is obtained, in a contactless manner, dispensing a known liquid quantity without any moving part in the assembly according to the invention and without any contact between the fluids to manipulate and the human controller of the process to which it can be applied. This assembly is suitable to release fluid, in particular oils and non-volatile oils, in any kind of chip, with an accurate control of volume of fluid released and/or with an accurate control of fluid release step during a process.

[0114] Besides, liquid dispensing may be implemented in parallel to deliver fluid simultaneously on several locations of a chip, as will be disclosed below.

[0115] For example, such assembly can be used for PCR, in such case, the fluid 3 to be release could be an oil and the gas 4 is preferably air. In that case, the channel 20 is in contact with oil on one side and with air on the other side where a well 112 for microfluidic chip could be positioned.

[0116] FIG. 2 is a perspective view of an array of caps C for an embodiment of assembly according to the invention. Each cap C is connected to the other thanks to two ring-shaped plastic connectors 13 placed on each side with reference to the direction of alignment of the array of caps C. The cap C is preferably in a polymeric material. It has base 11 with preferably a flat surface so as to allow the array of caps C to be set upside down laying on the base 11 in a stable position. Such stable position will permit filling the fluid 3 to be released by simply pouring it into the internal hollow part of the cap C. Another advantage of such flat base 11 is to serve as a support for mechanical stabilization of the assembly according to the invention if a stabilizing mean needs support to avoid assembly deformation during heating for example during thermocycles of a particular type of PCR using a microchip mechanically coupled to the assembly according to the invention. The cap C preferably ha a cylindrical shape but it can also have a conical shape. In a preferred embodiment, the walls 12 of the cap C have an elastic behavior so as to facilitate coupling with another part such as a fluid receiving vessel 2 in a fluid tight manner as depicted in FIG. 3.

[0117] FIG. 3 depicts a cross sectional view of an array of assemblies according to the invention with caps C mechanically coupled to a fluid receiving vessel 2. Two arrays of assemblies are represented, the plurality of parallel arrays of assemblies A are linked to one another by one longitudinal bridge 71. The longitudinal bridge 71 extends perpendicularly to the longitudinal alignment of assemblies A joining two parallel arrays to facilitate manipulation of multiple assemblies. This is useful if different analytes must be analyzed or processed for PCR for instance and a fluid must be released on the well 112.

[0118] In FIG. 3, which is a preferred embodiment, the non-compressible compartment 1 is obtained by fitting the cap C with its base 11 and lateral wall external surface 12, to a fluid receiving vessel 2 comprising its base 21, the channel 20 for fluid flow and lateral wall internal surface 22. The fitting is done so that the cap lateral wall external surface 12 and the fluid receiving vessel lateral wall internal surface 22 form a fluid tight seal, contacting each other via the wall surfaces. The channel 20 in in contact on one side with the fluid 3 to be released and on the other side with air in the volume of the loading well 112.

[0119] FIG. 4 is simply a perspective view of FIG. 3 for better understanding the double array of assemblies A according to the invention.

[0120] FIG. 5 focuses on the fluid receiving vessel 2 and its channel 20 for fluid flow. It represents two parallel arrays of fluid receiving vessel 2. The channel 20 is preferably located in the central position of the cylindrical base of fluid receiving vessel 2. It must not be facing the loading well outlet 111. Indeed, since the loading well 112 may contain droplets to be analyzed, it must be avoided to release a fluid directly in the loading well outlet 111 unless we want the fluid to be released to enter directly in the distribution area of the microfluidic chip microchannels (cf. FIG. 9).

[0121] In FIG. 5, one can also distinguish the two connecting bridges 71 and 72, that are here longitudinal bridges extending perpendicular to the parallel alignment array of assemblies A. each bridge has a projection perpendicular to the longitudinal extending bridge plane. Such projection presents a central section small than the extremities to improve flexibility of the connection. Indeed, deformations may take place when the assembly according to the invention is submitted to thermal cycles or high pressure and the connecting bridge must be able to accommodate such deformation.

[0122] FIG. 6 depicts two parallel arrays of fluid receiving vessel 2, one of the arrays being coupled with a corresponding array of caps according to the invention.

[0123] In FIG. 7, one can see an array of individual loading wells 112 along with their associated loading well outlet 111. Each loading well outlet 111 is offset with regards to the output of the fluid receiving vessel channel 20 output. This avoids releasing the fluid 3 directly into the microfluidic chip microchannels. It is here reminded that in a preferred embodiment according to the invention, the fluid to be released is not the one to be analyzed. If that was the case, aligning vertically the channel 20 and the loading well outlet 111 would be a preferred embodiment.

[0124] In FIG. 8 is depicted a microfluidic chip M with its networks 6. An array of assemblies according to the invention is set on top of the microfluidic chip M so to release a fluid 3 if necessary.

[0125] FIG. 9 is a perspective cut view along the line AA of FIG. 8 with the loading well 112 on top of a microfluidic chip M shown for clarity. An air tank 5 is also represented. Basically, the loading well 112 is configured to reduce the dead volume of a drop of sample (droplet) to be loaded in the microfluidic chip M. Typically, in a biphasic microfluidic chip, a continuous phase is loaded first and fills at least partially the microfluidic network. For instance, in the presence of an air tank 5, the microfluidic chip M is only partially filled with the continuous phase and the air tank 5 is globally filled with air, before placing a drop of dispersed phase (typically, a sample to analyze) in the loading well 112, at the continuous phase/air interface. Moving the sample to analyze to a defined location within the loading well 112 and trapping it at said defined location is required to perform a reproducible loading of the sample to analyze into the microfluidic network, while reducing the dead volume of the sample upon loading.

[0126] The air tank 5 is operatively coupled to the droplet chamber where the microfluidic channels 6 lead to the samples to be processed/analyzed.

[0127] We will now describe a method according to the invention where oil is the fluid to be released, the gas is gas and a layer of oil is to be dispensed in the volume of the loading well 112 where a droplet is to be processed/analyzed.

[0128] For instance; a droplet (not represented) is placed in a loading well 112 and is covered with a continuous phase that is here the same as the oil to release. The oil touches the bottom wall part of the loading well while deforming the continuous phase/air interface. Such deformation increases the continuous phase/air contact area, forming a meniscus. Due to surface tension, the system ultimately evolves toward lowering said continuous phase/air contact area.

[0129] This phenomenon moves and traps the droplet (not represented) towards the position of higher depth of the loading well 112, which is the loading well outlet. This droplet will be later injected into the loading well outlet, then the chip, by application of an external pressure. To prevent any evaporation phenomenon that may take place during subsequent thermal cycle due to a PCR process for example, a film of non-volatile oil has to be deposited in the loading well. This is done with assembly A.

[0130] Thus, to do so, the invention relates also to a method for forming an assembly A according to the invention, comprising the successive following steps: [0131] Filling a cap C comprising a base 11 and a lateral wall external surface 12 with the fluid 3 to be released, [0132] Fitting said cap C with a receiving vessel 2 comprising a channel 20 for fluid flow and lateral wall internal surface 22, so that the cap lateral wall external surface 12 and the fluid receiving vessel lateral wall internal surface 22 form a fluid tight seal.

[0133] Such method is detailed in FIG. 10 where, from top to bottom, a fluid to release 3 is first poured inside the cap C. One can notice that the cap C is laid base facing down on its basis 11 thanks to the flat surface of said base 11.

[0134] Then the complementary fluid receiving vessel 2 is coupled to the cap C so that the cap lateral wall external surface 12 and the fluid receiving vessel lateral wall internal surface 22 form a fluid tight seal as in FIG. 3, thus trapping the fluid to release 3 with gas 4 inside the non-compressible compartment 1.

[0135] In a further preferred embodiment, the array of assemblies according to the invention comprising a droplet to analyze/process is put into an apparatus comprising a pressure controller in a configuration where the cap C is on top of the receiving vessel 2. Then a pressure cycle is implemented so as to release the fluid 3 from the fluid receiving vessel 2 to the loading well 112 and simultaneously to inject droplet into the loading well outlet. Finally, a layer of fluid 3 is deposited in the loading well and prevent evaporation of the injected droplet.

[0136] As a first example of cycle, one can refer to FIG. 11 where: the initial pressure is defined as Pinit. In configuration A, the oil does not drop because the channel 20 does not allow a simultaneous double flow (air in, liquid out) and this is also due to the volume of the compartment 1 that is non compressible. In configuration B, the pressure is increased and the compartment 1 being non compressible, some ambient gas from the loading well 112 gets injected into the compartment 1 through the channel 20.

[0137] As soon as it enters into the compartment 1, the injected gas turns into bubbles and rises up thanks to gravity.

[0138] During subsequent pressure decrease back to initial pressure Pinit (configuration C), the compressible volume 4 (gas) expands and the compartment 1 being non compressible, the fluid 3 to be released, i.e. the oil, gets ejected out of the compartment 1 through the channel 20 down to the loading well 112.

[0139] This first example of cycle may be repeated several times. In particular, a cycle may be designed according to fluid 3 viscosity and surface tension, according to channel 20 and non-compressible compartment 1 dimensions so as to release one drop of fluid 3. Then, repeating the determined cycle allows to deliver a given number of drops, for instance two drop, three drops, four drops or five drops, depending on the size of the loading well 112 in which fluid 3 is released.

[0140] As a second example of cycle, instead of a cycle of pressure increase followed by pressure decrease down to the initial pressure Pinit, the pressure will first be decreased followed by pressure increase up to the initial pressure Pinit.

[0141] Referring to FIG. 12, at configuration A, the oil does not drop because the channel 20 does not allow a simultaneous double flow (air in, liquid out) and this is also due to the volume of the compartment 1 that is non compressible. In configuration B, the pressure is decreased, the compressible gas volume 4 inflates and since compartment 1 is non compressible nor extensible, the fluid to be released, i.e. oil, gets ejected out of the compartment 1 through the channel 20 down to the loading well 112.

[0142] During subsequent pressure increase back to initial pressure Pinit (configuration C), gas bubbles flow through channel 20. Since the compartment 1 is non compressible nor extensible, some ambient gas from the loading 112 get sucked into the compartment 1 through the channel 20. As soon as it enters into the compartment 1, the injected gas become bubbles and rise up thanks to gravity.

[0143] This second example of cycle may be repeated several times. In particular, a cycle may be designed according to fluid 3 viscosity and surface tension, according to channel 20 and non-compressible compartment 1 dimensions so as to release one drop of fluid 3. Then, repeating the determined cycle allows to deliver a given number of drops, for instance two drop, three drops, four drops or five drops, depending on the size of the loading well 112 in which fluid 3 is released.

[0144] With both cycles, a layer of oil is formed on the loading well surface covering it so as to prevent subsequent evaporation phenomenon.

[0145] As demonstrated, the method of contactless pressure-controlled fluid releasing according to the invention has the strong advantage of working with a thermocycler no matter if the cycle requires first a pressure increase or decrease. This offers significant flexibility in choosing the apparatus for the pressure cycle to release the fluid 3.

[0146] While various embodiments have been described and illustrated, the detailed description is not to be construed as being limited hereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the claims.

REFERENCES

[0147] 1—non-compressible compartment [0148] 11—Cap base [0149] 12—Cap lateral wall [0150] 13—connecting means [0151] 2—fluid receiving vessel [0152] 20—channel [0153] 21—fluid receiving vessel base [0154] 22—fluid receiving vessel lateral wall [0155] 3—fluid to be released [0156] 4—compressible fluid [0157] 5—Air tank [0158] 6—Microfluidic chip network [0159] 111—loading well outlet [0160] 112—well [0161] 71,72—connecting bridge [0162] M—Microfluidic chip