DEVICE AND METHOD FOR CREATING AN EMULSION

Abstract

Device for creating an emulsion consisting of a dispersed phase in the form of drops in a continuous phase, the device comprising: a motion generator (11) in order to put into motion at least one first fluid (3) intended to form the dispersed phase; a first channel (21) inside which the first fluid (3) put into motion can flow, the first channel (21) extending towards an output orifice (23) through which the first fluid is injected into at least one second fluid (5) intended to form the continuous phase; a variation system (40) for varying the internal volume (Vi) of the first channel (21) over time.

Claims

1. A device for creating an emulsion composed of a phase dispersed in the form of drops in a continuous phase, the device comprising: a motion generator in order to put into motion at least one first fluid which is intended to form a dispersed phase; a first channel inside which the first fluid put into motion can flow, the first channel extending towards an output orifice via which the first fluid is injected into at least one second fluid which is intended to form the continuous phase; a variation system in order to make an interior volume of the first channel vary with time; and an electronic control circuit comprising: a first control unit to control the motion generator, which is configured to generate a first signal with first extrema, to make a flow of the first fluid in the first channel vary with time; a second control unit to control the variation system, which is configured to generate a second signal with second extrema, to make the interior volume of the first channel vary with time; and a coordination system connected to the control units, and configured to associate first and second extrema two by two, with a predetermined temporal offset between two associated extrema.

2. The device according to claim 1, wherein a first extremum corresponds to a temporary injection of the first fluid into the second fluid.

3. The device according to claim 1, wherein a second extremum corresponds to an increase followed by a decrease of the interior volume of the first channel.

4. The device according to claim 1, wherein the first channel is a microchannel.

5. The device according to claim 1, wherein the variation system is configured to pinch or compress a deformable portion of the first channel, in order to make the interior volume of the first channel vary.

6. The device according to claim 1, wherein the first and second control units are configured respectively such that the first signal generated is a signal wherein the main extrema appear periodically, and such that the second signal generated is a signal in which the main extrema appear periodically, the periods of these signals being equal.

7. The device according to claim 1, wherein the first and second control units are configured to generate first and second signals which vary according to the size and/or the form of the drops which are formed by the first fluid in the second fluid.

8. The device according to claim 1, further comprising a detector to detect the size and/or the form of the drops formed by the first fluid in the second fluid.

9. The device according to claim 1, wherein the motion generator comprises: a reservoir in which the first fluid is maintained under pressure, with the reservoir supplying the first channel by means of a supply duct; and a valve which is fitted between the supply duct and the first channel, said valve being controllable by the control unit of the motion generator, so as to allow the first fluid to pass intermittently into the first channel.

10. The device according to claim 1, wherein for associated first and second extrema, the predetermined temporal offset between these two extrema is between −2 s and +2 s.

11. The device according to claim 1, comprising: a second channel inside which the second fluid can flow, and another motion generator in order to put the second fluid into motion continuously in the second channel, wherein the output orifice of the first channel opens into the second channel.

12. The device according to claim 11, wherein the second channel has a widening of cross-section downstream from the output orifice of the first channel.

13. A method for creating an emulsion composed of a dispersed phase in the form of drops in a continuous phase, comprising: putting into motion a first fluid which is intended to form the dispersed phase, so that the first fluid flows inside a first channel extending towards an output orifice via which the first fluid is injected into a second fluid intended to form the continuous phase; generating a first signal with first extrema, in order to make a flow of the first fluid in the first channel vary with time; generating a second signal with second extrema, in order to make an interior volume of the first channel vary with time; and coordinating the first and second signals, so as to associate first and second extrema two by two, with predetermined temporal offset between two associated extrema.

14. The method according to claim 13, wherein a first extremum corresponds to a temporary injection of the first fluid into the second fluid.

15. The method according to claim 13, wherein a second extremum corresponds to an increase followed by a decrease of the interior volume of the first channel.

16. The method according to claim 13, wherein the first signal generated is a signal wherein the main extrema appear periodically, and the second signal generated is a signal wherein the main extrema appear periodically, the periods of these signals being equal.

17. The method according to claim 13, wherein the first fluid is aqueous and the second fluid is oily, or conversely.

18. The method according to claim 13, wherein the drops of the dispersed phase are spherical or spheroidal, with a mean diameter greater than 0.1 mm, or they have a different form, with a volume greater than that of a sphere having a diameter of 0.1 mm.

19. The method according to claim 13, wherein the drops of the dispersed phase are spherical or spheroidal, with a diameter smaller than 30 mm, or they have a different form, with a volume smaller than that of a sphere having a diameter of 30 mm.

20. An emulsion comprising a phase dispersed in the form of drops in a continuous phase, obtained by the method according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The appended drawings are schematic, and are not necessarily to scale; their objective is above all to illustrate the principles of the invention. In these drawings, from one figure (fig) to another, elements (or parts of elements) which are identical are indicated by the same reference signs.

[0067] FIG. 1 This figure represents an example of a device according to one embodiment.

[0068] FIG. 2 This figure is a detailed view of FIG. 1 representing an example of a variation system according to one embodiment.

[0069] FIG. 3 This figure is a series of graphs (A) to (D) representing respectively: (A) an example of the control signal sent to the motion generator by its control unit; (B) an example of the control signal sent to the variation system by its control unit; (C) the temporal variation of the flow of first fluid in the first channel; and (D) the temporal variation of the interior volume of the first channel.

[0070] FIG. 4 This figure is a photograph of an emulsion created by means of the device in FIG. 1, without the variation system being activated.

[0071] FIG. 5 This figure is a photograph of an emulsion created by means of the device in FIG. 1 with the variation system activated and controlled as illustrated in FIG. 4.

[0072] FIG. 6 This figure is a diagram illustrating the formation of drops at the output of the first channel in the device of FIG. 1 according to an embodiment.

[0073] FIG. 7 This figure is a diagram representing an example of the geometry of the second channel.

[0074] FIG. 8 This figure is a photograph of an example of an emulsion created by means of a device according to the invention.

[0075] FIG. 9 This figure is a photograph of another example of an emulsion created by means of a device according to the invention.

DETAILED DESCRIPTION OF EXAMPLES

[0076] Examples of the device and of the method proposed are described in detail hereinafter with reference to the appended drawings. These examples illustrate the characteristics and the advantages of the invention. It should however be remembered that the invention is not limited to these examples. FIG. 1 represents an example of a device 10 for creating an emulsion 1 composed of a phase dispersed in the form of drops 3A in a continuous phase 5A. This emulsion 1 is collected, for example, in a container 7.

[0077] The device 10 comprises: [0078] a motion generator 11 in order to put into motion at least one first fluid 3 which is intended to form the dispersed phase; [0079] a first channel 21 inside which the first fluid 3 put into motion can flow, with the first channel 21 extending from the motion generator 11 to an output orifice 23 via which the first fluid 3 is injected into at least one second fluid 5 which is intended to form the continuous phase 5A; [0080] a variation system 40 for making the interior volume of the first channel 21 vary with time; and [0081] an electronic control circuit 50 which makes it possible to command, or control, the motion generator 11 and the variation system 40.

[0082] In this example, the motion generator 11 comprises a reservoir 15 of first fluid 3.

[0083] This reservoir 15 is pressurized by means of a source of pressure 14, for example a microfluidic pressure controller (e.g. the controller sold under the name “Flow EZ” by the company Fluigent, France), and is associated with a solenoid valve 16, for example an all-or-nothing solenoid valve (e.g. the solenoid valve which is sold under the name “VX243AZ3AAXB” by the company SMC, Japan). The reservoir 15 supplies the first channel 21 by means of a supply duct 17, with the solenoid valve 16 being situated at the connection between the supply duct 17 and the first channel 21. The controlled opening and closure of the solenoid valve 16, which takes place alternately, makes it possible to make the first fluid 3 advance intermittently in the first channel 21. The first channel 21 extends from the solenoid valve 16 (which forms part of the motion generator 11) as far as the output orifice 23. The first channel 21 opens into a second channel 25 in which the second fluid 5 circulates. The injection of the second fluid 5 into the second channel 25 is symbolized by the arrow B in FIG. 1. The second channel 25 opens into the container 7. In the example, the first and the second channels 21, 25 are connected in the form of a “T”. These channels 21, 25 may be microchannels.

[0084] The variation system 40 is situated downstream from the solenoid valve 16, in the direction of circulation of the first fluid 3. An example of a variation system 40 is illustrated in FIG. 2. This system 40 compresses a deformable portion 21A of the first channel 21, in order to vary the interior volume of the first channel. This portion 21A of the first channel is elastically deformable, and can thus regain its initial form by itself, completely or partly, when it is no longer compressed. The system 40 may for example be an actuator 41 with an electromagnet comprising a rod 42 which is mobile in translation, as illustrated by the double arrow in FIG. 2. A system of this type is sold under the name “Small linear solenoid for intensive use” by the company Mecalectro. In another embodiment (not shown) the solenoid valve 16 and the variation system 40 are combined in a single system.

[0085] The controlled displacement of the rod 42 makes it possible to compress the portion 21A in a controlled manner. When the portion 21A of the first channel 21 is compressed by the rod 42, the interior volume of the first channel 21 decreases. Conversely, when it is no longer compressed, the portion 21A regains its initial form, and the interior volume of the first channel 21 increases, thus creating the required aspiration effect.

[0086] The electronic control circuit 50 comprises a control unit 56 which is configured to generate a first signal 57 with first extrema which control the generator 11 so as to generate variations of the flow of first fluid 3 in the first channel 3A, with each first extremum corresponding to a temporary injection of the first fluid 3 into the second fluid 5, via the output orifice 23 of the first channel 21. Hereinafter, reference is made to the primary pulse in order to designate the increase and decrease of the signal around a first extremum. In the example, the control unit 56 controls the opening and closure of the solenoid valve 16.

[0087] The electronic control circuit 50 also comprises a control unit 54 which is configured to generate a second signal 58 with second extrema which control the variation system, so as to generate variations of the interior volume of the first channel 21, with each second extremum corresponding to an increase followed by a decrease of the interior volume of the first channel 21. Hereinafter, reference is made to the secondary pulse in order to designate the increase and decrease of the signal around a second extremum. In the example, the control unit 54 controls the actuator 41, and thus the compression of the portion 21A of the first channel 21 by the rod 42.

[0088] The electronic control circuit 50 also comprises a coordination system 60 which is connected to the control units 54, 56, and is configured to associate a secondary pulse with a primary pulse, with predetermined temporal offset between the two associated pulses. This aspect is illustrated in FIGS. 3 to 6. In the example, a second extremum is associated with each first extremum.

[0089] The graphs A to D in FIG. 3 represent respectively:

A: an example of a first control signal sent to the solenoid valve 16 by the control unit 56, this first signal being schematized by the arrow 57 in FIG. 1;
B: an example of a second control signal sent to the variation system 40 by the control unit 54, this second signal being schematized by the arrow 58 in FIG. 1;
C: an example of variation with time of the flow of first fluid 3 in the first channel 21;
D: an example of variation with time of the interior volume of the first channel 21.

[0090] The graph A of FIG. 3 represents, on the y-axis, the first control signal 57 for the solenoid valve 16, and, on the x-axis, the time expressed in milliseconds. The control signal 57 which is sent by the control unit 56 is a square signal which varies between a first and a second value, in this case between 0 and 1. When the signal is equal to 1, it commands the opening of the solenoid valve 16, and consequently the putting into motion of the first fluid 3 in the first channel 3A (cf. graph C), and the start of the injection of the first fluid 3 into the second fluid 5. When the signal 57 is equal to 0, it commands the closure of the solenoid valve 16, and consequently the progressive stoppage of the first fluid 3 in the first channel 3A, and the end of the injection of the first fluid 3 into the second fluid 5.

[0091] The example of a first control signal 57 of the graph A in FIG. 3 is composed of a succession of first extrema according to the invention, with each first extremum corresponding to a limited time-lapse during which the signal 57 commands the putting into motion of the first fluid (i.e. during which the value of the signal 57 is maximum and, in this case, equal to 1).

[0092] The graph B in FIG. 3 represents on the y-axis the second control signal 58 for the variation system 40, and, on the x-axis, the time expressed in milliseconds. The control signal 58 which is sent by the control unit 54 is a square signal which varies between a first and a second value, in this case between 0 and 1. When the signal 58 is equal to 0, it commands the descent of the rod 42 (cf. FIG. 2), and consequently the compression of the first channel 21. When the signal is equal to 1, it commands the raising of the rod 42, and consequently the release or relaxing of the first channel 21, which regains its initial form by means of elasticity.

[0093] The example of a second control signal 58 of the graph B in FIG. 3 is composed of a succession of second extrema according to the invention, with each second extremum corresponding to a limited time-lapse during which the first channel 21 is no longer compressed (i.e. during which the value of the signal 58 is maximum and, in this case, equal to 1).

[0094] In the example of FIG. 3, each second extremum starts after the end of the associated first extremum. There is therefore a temporal offset Dt between the start of the secondary pulse and the end of the associated primary pulse. In the example, this offset Dt is less than 100 milliseconds (ms) and approximately equal to 50 ms. The variation of the first control signal 57 (graph A) results in the variation of the flow of first fluid 3 in the first channel 21 represented in graph C. Graph C represents on the y-axis the flow Dv of the first fluid 3 in the first channel 21, expressed in arbitrary flow units, and, on the x-axis, the time t expressed in ms. The variation of the flow Dv is a consequence of the pulses (graph A) of the first signal 57. The flow Dv increases when the first signal 57 is 1, and it decreases when the first signal 57 goes to 0.

[0095] The variation of the second control signal 58 (graph B) results in the variation of the interior volume of the first channel 21 represented in graph D. Graph D represents, on the y-axis, the interior volume Vi of the first channel 21 expressed as an arbitrary volume unit, and, on the x-axis, the time t expressed in milliseconds. The variation of the interior volume Vi is a consequence of the secondary extrema: during the compression of the first channel 21, the volume Vi decreases and, during the relaxation, the volume Vi increases and returns to its initial value. It will be noted that the negative flow associated with the start of a second pulse (graph C) is derived from the aspiration phenomenon previously described.

[0096] The increase of the interior volume Vi of the first channel 21 gives rise to aspiration of the first fluid 3 at the output opening 23 of the first channel 21. As a result of the coordination created between this aspiration and the movement of the first fluid 3, the aspiration at the output opening 23 intervenes rather towards the end of the injection of the drop 3A, which makes the tail of the drop 3A fragile, and the drop becomes detached sooner, with a shorter tail.

[0097] In order to better understand the phenomenon in question, a diagram representing the formation of a drop 3A of first fluid 3 at the output orifice 23 of the first channel 21 is given in FIG. 6. As illustrated, when a drop becomes detached from the output orifice 23, a tail 9 forms at the rear of the drop, which will tend to break up into a plurality of secondary drops or satellites 19 which are smaller than the main drop. FIG. 6 illustrates a “conventional” formation of drops 3A, without aspiration.

[0098] Contrary to what is illustrated in FIG. 6, the invention creates an aspiration effect at the output orifice 23, which makes the tail 9 of the drop 3A fragile. As a consequence, the drop 3A becomes detached sooner than in the absence of aspiration of this type, with a shorter tail 9. The tail is thus less liable to break up into satellite drops 19.

[0099] It will be noted that, in certain embodiments, in addition to the aspiration effect, the output orifice 23 of the channel 21 can be made of a particular material, or it can be subjected to surface treatments in order to have desired physical and chemical properties (e.g. hydrophobic or hydrophilic, etc.), according to the fluids 3, 5 used, in order to reduce the number of satellite drops 19 during the detachment of these drops 9. Similarly, the channel 25 of the second liquid 5 can also be made of a particular material, or it can be subjected to surface treatments in order to have desired chemical and physical properties (e.g. hydrophobic or hydrophilic) in order to reduce the risk of drops 3A getting caught on the interior walls of the channel.

[0100] In addition, in certain embodiments, the second channel 25 has a widening of cross-section 25A downstream from the output orifice 23 of the first channel 21, as represented in FIG. 7. A widening 25 of this type makes it possible to reduce the generation of satellite drops 19.

[0101] For example, for a second channel 25 with a circular cross-section, the ratio D2/D1 between the inner diameter D2 of the channel after widening 25A and the inner diameter D1 of the channel before widening 25A is between 1 and 20. In addition, the distance L between the center of the output orifice 23 and the start of the widening 25A is less than 50 mm. As a variant or as a complement, the distance L can be 10 times smaller than, in particular 5 times smaller than, and more particularly twice as small as the size of the drops.

[0102] The angle of widening α of the second channel 25 may be between 5° and 90°. According to a specific example, D1=3 mm, D2=8 mm, L=3 mm and α=59°.

[0103] The parameters D2, D1, D2/D1, L and α can be adjusted, inter alia, according to the size of the drops 3A, the frequency of generation of the drops, the physical and chemical properties, as well as the flows of the fluids 3, 5 implemented.

[0104] FIG. 4 is a photograph of the drops circulating in the device 10 in FIG. 1, without the variation system 40 being activated, i.e. without the portion 21A of channel being compressed, and thus without an aspiration phenomenon. In contrast, FIG. 5 is a photograph of an emulsion created by means of the device in FIG. 1 with the variation system 40 activated and controlled as illustrated in the graph B of FIG. 3. In both cases (FIGS. 4 and 5), the motion generator 11 has been activated and controlled as illustrated in the graph A of FIG. 3.

[0105] As can be seen in the photo in FIG. 4, without a variation system 40 activated, and thus without aspiration, the drops 3A have a tail 9 which breaks up into a plurality of satellite drops 19 smaller than the main drop. In contrast, as illustrated in FIG. 5, with the variation system 40 activated, the phenomena of drop tails or satellite drops disappear. Optionally, the device 10 in FIG. 1 can comprise a feedback loop which is formed in particular by a detector 70 connected to the electronic control circuit 50. The detector 70 makes it possible to detect the size and/or the form of the drops 3A formed by the first fluid 3 in the second fluid 5. Information concerning the size and/or the form of the drops 3A is sent by the detector 70 to the control units 54, 56. According to this information, the control units 54, 56 adapt the duration and/or the frequency of the first and second extrema, or/and the offset Dt between the associated extrema, or/and also the volume of variation in the variation system 40. FIGS. 8 and 9 are photographs of emulsions created by means of a device according to the invention, of the same type as the one in FIG. 1. The emulsion in FIG. 8 is such that the drops which constitute it have a mean diameter of approximately 1 mm, and the volume concentration of these drops is approximately 0.6%. In FIG. 9, the drops of the emulsion have a mean diameter of approximately 2.9 mm, and the volume concentration of these drops is approximately 35%.

[0106] The embodiments or examples which are described in the present invention are given by way of non-limiting illustration, and in the light of this invention persons skilled in the art can easily modify these embodiments or examples or envisage others, while remaining within the scope of the invention. In particular, persons skilled in the art could easily envisage variants comprising only some of the features of the embodiments or examples previously described, if these features alone are sufficient to provide one of the advantages of the invention. In addition, the different features of these embodiments or examples may be used alone or combined with one another. When they are combined, these features may be combined as described above or differently, since the invention is not limited to the specific combinations described herein. In particular, unless otherwise stated, a characteristic described in relation with one embodiment or example can be applied in an analogous manner to another embodiment or example.