WO2005107946A2

WO2005107946A2 - Device for the production of microdroplets by means of liquid ejection and method of producing one such device

Info

Publication number: WO2005107946A2
Application number: PCT/FR2005/000908
Authority: WO
Inventors: Brice Lopez
Original assignee: Brice Lopez
Priority date: 2004-04-19
Filing date: 2005-04-14
Publication date: 2005-11-17
Also published as: WO2005107946A3; FR2868966B1; FR2868966A1; EP1765499A2

Abstract

The invention relates to a device for the production of microdroplets by means of liquid ejection. The inventive device consists of a sealed chamber (1) comprising a liquid inlet (2) and at least one liquid outlet (3) and, for example, an actuating piezoelectric plate (7) which causes droplets (10) to be ejected through the outlet (3). The chamber (1) is defined mainly by lower (5) and upper (6) rigid plates and an essentially-annular, thin deformable seal (4) which is disposed between the plates (5, 6) and which forms a lateral wall of the chamber (1). The piezoelectric plate (7) causes a relative movement between all of the lower (5) and upper (6) plates in terms of bending and/or translation, by compressing the deformable seal (4). According to the invention, the lower (5) and upper (6) plates are stiffer than the deformable seal (4).

Description

Device for producing micro-drops by ejecting liquid and method for producing such a device

Technical field of the invention

The invention relates to a device for producing micro-drops by liquid ejection comprising a sealed chamber delimited mainly by lower and upper plates and by a side wall, the chamber having at least one liquid inlet and at least one liquid outlet. , the device comprising actuating means acting on at least one of the lower and upper plates to modulate the volume of the chamber so as to form drops at the outlet.

State of the art

The devices for producing micro-drops by ejecting liquid through an orifice make it possible to generate drops of liquid whose volume is typically between a few picoliters and a few nanoliters depending mainly on the size of the orifice. The formation of the drops is conventionally ensured by the generation of a pressure by means of a piezoelectric element. There are typically two modes of drop formation: A first mode works by breaking a continuous jet of liquid, where the natural instability of the jet is controlled by the generation of a pressure modulated at a frequency to obtain a train droplets, uniform in size. This mode of gout formation is presented, for example, in the document US5337071. A second mode works by ejecting a single drop on each pulse of a pressure generation system (drops on demand), where a filament of liquid is rapidly propelled out of the device. This filament contracts under the effect of surface tension forces to form a drop of liquid. This mode of formation of single drops is presented, for example, in the document US6367925. Such devices find applications in many fields such as chemistry, pharmacy, biology, optics, micro-machining, etc. Among the different applications, one can cite the manufacture of micro-beads, the synthesis of DNA or the manufacture of micro-lenses by polymer ejection. The devices are often based on the technologies used for inkjet printing, in particular on the implementation of silicon, glass and ceramics by micro-machining or photoengraving. These technologies lead to complex and expensive devices.

Furthermore, the use of various industrial liquids, containing several phases or even solid particles, leads to blockage of outlet nozzles, which often requires replacement of the entire device.

The document US Pat. No. 6,367,925 describes a device for ejecting micro-drops comprising a tube of rectangular section having a flat side on which a piezoelectric material is disposed. Applying voltage pulses to the piezoelectric material allows micro-drops to be ejected. The tube has particular geometric shapes, the manufacture of which is expensive and difficult.

Document DE19617924 describes a liquid micro-droplet ejection system comprising a sealed chamber having a liquid inlet and liquid outlets. A liquid excitation device causes the drops to be ejected through the outlets. This system is complex and difficult to implement.

Document WO03089138 describes a microfluidic system comprising an elastomer layer in which channels are molded. The walls in contact with the fluid mainly consist of elastomer. The actuation by piezoelectric means modulates the passage of the liquid in the channels. This system makes it possible to move a liquid by pumping. The walls of the chambers in which the fluid is located, mainly made of flexible materials, dampen the pressure waves and do not allow the ejection of drops of liquid. The document US5828394 describes a drop ejection device comprising a substrate, a cylindrical side wall and an upper elastic membrane, defining a fluid reservoir. A piezoelectric plate having an ejection orifice is disposed on the membrane. A fluid inlet is formed in the side wall.

Other operating principles, for example by radial deformation, have been proposed. The document EP1116590, for example, describes an ink jet writing head using a stack of piezoelectric annular bodies and intermediate elements. The stack is arranged between a lower plate comprising an ink outlet and an upper plate comprising an ink inlet, so as to form a chamber. The actuation of the piezoelectric structure causes a radial deformation, allowing to modulate the interior volume of the chamber.

Subject of the invention

The object of the invention is to remedy these drawbacks and, in particular, to make it possible to produce a simple and effective device for producing micro-drops by ejection of liquid, at low cost and facilitating the change of components of the device.

According to the invention, this object is achieved by the appended claims and, in particular, by the fact that the side wall is constituted by a substantially annular deformable seal of small thickness, disposed between the plates so as to allow the relative displacement of the all of the plates, in flexion and / or in translation, by crushing the joint, the lower and upper plates being more rigid than the deformable joint. Brief description of the drawings

Other advantages and characteristics will emerge more clearly from the description which follows of particular embodiments of the invention given by way of nonlimiting examples and represented in the appended drawings, in which:

Figures 1 and 2 show, respectively in top view and in section along the axis A-A, a particular embodiment of a device according to the invention.

Figures 3 and 4 show, in section, two other particular embodiments of a device according to the invention.

FIG. 5 illustrates a particular embodiment of a liquid outlet of a device according to the invention.

FIG. 6 illustrates a particular embodiment of a substantially annular deformable joint of a device according to the invention.

Figure 7 schematically illustrates the operation of a device according to the prior art.

Figures 8 and 9 schematically illustrate two particular modes of operation of the device according to the invention.

Description of particular embodiments

The device for producing micro-drops by ejection of liquid shown in FIGS. 1 and 2 comprises a sealed chamber 1, having an inlet 2 for liquid and an outlet 3 for liquid. Chamber 1 is delimited mainly by rigid lower 5 and upper 6 plates and by a side wall constituted by a deformable seal 4 substantially annular of small thickness. The deformable seal 4 is disposed between the rigid lower 5 and upper 6 plates and has a flexibility allowing the relative displacement of all of the plates 5 and 6, in bending and or in translation, by crushing the deformable seal 4. The lower plates 5 and upper 6 are more rigid than the deformable seal 4, which in particular ensures that the deformable seal 4 is deformed and crushed between the plates 5 and 6. In FIG. 2, the rigid lower 5 and upper 6 plates are parallel. The deformable seal 4 is substantially annular and disposed between the plates 5 and 6.

The deformable seal 4 shown in Figure 2 is constituted by an elastomer ring. The sealed chamber 1 is then formed by the lower face of the upper plate 6, by the upper face of the lower plate 5 and by the internal lateral walls of the deformable seal 4. The height of the chamber 1, corresponding to the thickness of the deformable joint 4, is very small compared to the diameter of the chamber 1, defined by the inside diameter of the substantially annular joint 4. Thus, the sealed chamber 1 is mainly constituted by rigid materials, in particular by the plates 5 and 6. In FIGS. 1 and 2, the lower rigid plate 5 serves as a support for the other elements of the device and the outlet 3 for liquid is formed in the bottom plate 5.

The device according to the invention comprises an actuator, preferably piezoelectric, acting on at least one of the lower 5 and upper 6 plates to modulate the volume of the chamber so as to form drops 10 at the outlet 3. Thus, the liquid is excited, for example by displacement of at least one of the lower 5 and upper 6 plates.

In the particular embodiment shown in Figures 1 and 2, the upper plate 6 is constituted by a piezoelectric plate 7, electrically excited on its lower and upper faces by means of lower 8 and upper 9 electrodes to which a voltage is applied electric Vex excitation. Thus, the piezoelectric plate 7 moves towards the interior of the chamber 1 and causes the formation of the drops 10 at the outlet 3 by a volume modulation of the chamber 1 and, possibly, by generation of a propagating pressure wave. , in bedroom 1, from top to bottom. The piezoelectric plate 7 then causes relative displacement of the rigid plates lower 5 and upper 6 and, thus, the excitation of the liquid. In the particular embodiment shown, this movement is transverse, that is to say perpendicular to the plates. When the excitation of the liquid is caused on the side of the upper plate 6, the liquid outlet 3 is preferably formed in the lower plate 5, which has in particular the advantage of obtaining better control of the drops. Indeed, if a liquid outlet is formed in the piezoelectric plate 7, drops of liquids can deposit around the orifice and, by their inertia, modify the behavior of the piezoelectric plate 7 and, for example, change the frequency and the size of the drops ejected.

The lower 8 and upper 9 electrodes can be connected to the upper face of the piezoelectric plate 7. The lower plate 5 is preferably made of a thermoplastic material possibly comprising a metal insert into which the outlet orifice 3 will be drilled. lower plate 5 preferably has a thickness of the order of 3 mm and sides of the order of 30mm. In the particular embodiment shown in Figures 1 and 2, the deformable seal consists, for example, of an elastomer ring. The thickness of the deformable joint 4 is preferably between 0.02mm and 2mm.

The application of a controlled pressure at the inlet 2 of chamber 1 makes it possible to control the position of the meniscus (in the drop-on-demand mode) or the liquid flow rate (in the jet break mode) at the outlet 3. The inlet 2 can, for example, be connected to a tank of liquid in slight depression or under pressure, for example of the order of 1 bar. Inlet 2 and outlet 3 have, for example, a cross section between 0.003 and 3 mm ² . The geometry of the inlet 2 is calculated in order to allow a sufficient flow of the liquid to supply the chamber 1 as the drops 10 are ejected through the outlet 3. Furthermore, the geometry of the inlet 2 is such that the quantity of liquid emerging through the inlet 2 during the generation of pressure does not affect the ejection of the drops 10 through the outlet 3.

In Figure 3, the upper plate 6 is constituted by a flat metal plate 1 1 on which is disposed the piezoelectric plate 7, which is thus protected from the liquid, possibly chemically aggressive. The metal plate is traditionally made of brass. For certain applications, it can be covered with a protective layer (in Teflon for example) or else be made up of a chemically resistant material (stainless steel for example). The assembly of the piezoelectric plate 7 and the flat metal plate 11 can be constituted by a sound vibrator (English term: "buzzer") as used for signaling devices. In the particular embodiment shown in Figure 3, the lower plate 5 has a groove 12, substantially annular in the plane of the plate 5, in which is positioned the deformable seal 4, constituted, for example, by an elastomer O-ring . The groove 12 can, for example, be machined in the lower plate 5 or in the upper plate 6, before assembly of the device. It is also possible to machine grooves 12 in each of the lower 5 and upper 6 plates. In the embodiment shown in FIG. 3, the inlet 2 for liquid is formed in the lower plate 5.

In Figures 1 to 3, the device comprises a clamping ring 13 disposed on the upper plate 6 and making it possible to disassemble and reassemble the ejection device quickly, for example to exchange parts. The clamping ring 13 and the bottom plate 5 can be fixed, for example, by screws 14, as shown in Figures 1 and 2, by a latching mechanism 15, as shown in Figure 3, or by any other means fixing, preferably reversible, without gluing or welding.

In FIG. 4, five orifices formed in the lower plate 5 constitute a plurality of liquid outlets 3. A stack (English term: "stac") of piezoelectric plates 7 is placed in contact with the upper plate 6.

In FIG. 5, the liquid outlet 3 is constituted by a groove 16 disposed at the interface between the deformable seal 4 and the lower plate 5, in particular in the lower plate 5. The groove 16 can also be disposed in the upper plate 6 or in the deformable joint 4.

In FIG. 6, the liquid outlet 3 is constituted by an opening 17 formed in the deformable joint 4 and having, for example, a square section of 70 micrometers on the side. The two particular embodiments of the liquid outlet 3 shown in FIGS. 5 and 6 make it possible to superpose several devices for producing micro-drops of liquid, the drops of liquid being ejected laterally. The device obtained has a small spacing between the outlets 3. It is preferably arranged vertically. The applications of such a device can, for example, be inkjet printing or high throughput screening.

The invention is not limited to the embodiments shown. In particular, the sealed chamber 1 can comprise several liquid outlets 3, produced in the lower plate 5 and / or the upper plate 6 and / or in the deformable joint 4. The liquid inlet 2 can comprise one or more orifices and can be formed both in the lower plate 5 than in the upper plate 6 or in the deformable joint 4. Furthermore, the actuation or pressure means can be constituted by any actuator or mechanism making it possible to exert pressure perpendicularly to the upper plate 6 and preferably placed above the upper plate 6. The actuator can, for example, be glued, so as to obtain a displacement in bending, or be in free contact, so as to transmit a longitudinal and or transverse movement to the plate. The relative displacement of the lower 5 and upper 6 rigid plates is preferably a relative displacement transverse to the planes of the plates. However, one can also consider a displacement of one of the plates in its plane, so as to cause a shearing effect of the liquid.

The device allows the ejection of liquids whose viscosity and surface tension can vary over a wide range thanks to the large contact surface between the liquid and the upper plate 6 and, thus, the piezoelectric plate 7 or the actuator d pressure excitation. The drops produced by the device according to the invention can be obtained for example by breaking a capillary jet (continuous jet) or else by punctual ejection of a drop (drops on request).

The piezoelectric plate 7 constitutes an actuator or a transducer making it possible to generate a vibration. The device can operate outside the resonant frequency of the transducer. The performance of the device is thus not very sensitive to variations in loads on the transducer. Consequently, the device can operate at very low frequency for applications where it is desired to deposit a drop occasionally. For example, a single voltage window of a amplitude of 50V and a width of 100 μs produces the ejection of a single drop through an orifice of 150y / m.

Thanks to better efficiency at low frequency of the device according to the invention, the diameter of the liquid outlet 3 can be greater than the diameter of a device according to the prior art, which makes it possible to generate larger drops of liquid. The outlet orifice preferably has a diameter of between 0.03mm and 0.3mm for the drop-on-demand mode and between 0.03 and 3mm for the continuous jet mode. In drop-on-demand mode, the ejected drops can thus have a volume of up to 25nl.

According to document US5828394, as shown in FIG. 7, the upper membrane 18 being elastic and the side wall 19 being rigid, the actuating means cause a deformation represented by an arrow 20. The rest position of the membrane 18 is shown by a dotted line 21. It is a deformation only of the central part 18a of the membrane 18, while the side wall 19, the substrate 22 and the periphery 18b of the membrane 18 remain stationary and do not deform. There is an embedding connection between the periphery 18b of the membrane 18 and the side wall 19. This effect is notably due to the elasticity of the membrane 18 which is greater than the elasticity of the side wall 19 which is rigid and which thus immobilizes the periphery 18b of the membrane 18.

In the device according to the invention, the rigid lower 5 and upper 6 plates are more rigid than the deformable joint 4, which allows a displacement in translation and / or in bending of all of one of the plates 5 and 6 under the action of / of the transducer and, thus, a relative displacement of all of the plates 5 and 6 in bending and / or in translation, accompanied by a deformation and a crushing of the deformable joint 4. As shown in FIGS. 8 and 9, thanks at the deformable joint 4, the entire upper plate 6 can be bent easily. There is a pivot connection between the upper plate 6 and the deformable seal 4. The force applied to the plates 5 and / or 6 can thus be lower than in the device according to document US5828394. The bending of the whole of the upper plate 6 is represented by an arrow 23, in FIG. 8, and the position of rest of the upper plate 6 is represented by a dotted line 24. The translation of the whole of the upper plate 6 is represented by an arrow 25, in FIG. 9, and the rest position of the upper plate 6 is represented by a dotted line 26.

The rigid plate or plates 5 and / or 6 moving under the action of the transducer (s) is preferably made of a material whose elastic modulus is between 1 and 300GPa (metal, ceramic, glass, thermoplastic ,. ..). The deformable joint preferably consists of a material whose elastic modulus is between 0.0005 and 0.1GPa, for example by an elastomer.

Unlike the device according to the invention, in order to obtain an effective volume modulation, the side wall of the chamber described in document EP1116590 must not have a small thickness.

Claims

claims

1. Device for producing micro-drops by ejection of liquid comprising a sealed chamber (1) delimited mainly by lower (5) and upper (6) plates and by a side wall, the chamber (1) having at least one inlet (2) of liquid and at least one outlet (3) of liquid, the device comprising actuating means acting on at least one of the lower (5) and upper (6) plates to modulate the volume of the chamber so as to forming drops (10) at the outlet (3), device characterized in that the side wall is constituted by a deformable seal (4) substantially annular of small thickness, disposed between the plates (5, 6) so as to allow the relative displacement of all the plates (5, 6), in flexion and / or in translation, by crushing the deformable joint (4), the lower (5) and upper (6) plates being more rigid than the deformable joint (4 ).

2. Device according to claim 1, characterized in that the actuating means comprise a piezoelectric plate (7).

3. Device according to claim 2, characterized in that the upper plate

(6) is constituted by the piezoelectric plate (7).

4. Device according to claim 2, characterized in that the upper plate

(7) is constituted by a metal plate (11) on which the piezoelectric plate (7) is disposed.

5. Device according to any one of claims 1 to 4, characterized in that the outlet (3) of liquid is formed in the lower plate (5).

6. Device according to any one of claims 1 to 4, characterized in that the outlet (3) of liquid consists of a groove (16) disposed at the interface between the deformable seal (4) and one of lower (5) and upper (6) plates.

7. Device according to any one of claims 1 to 4, characterized in that the outlet (3) of liquid is constituted by an opening (17) formed in the deformable seal (4).

8. Device according to any one of claims 1 to 7, characterized in that it comprises a clamping ring (13) disposed on the upper plate (6) and means for fixing the clamping ring (13) and of the lower plate (5).

9. Device according to any one of claims 1 to 8, characterized in that the deformable seal (4) is constituted by an O-ring or by an elastomer ring.

10. Device according to any one of claims 1 to 9, characterized in that at least one of the lower (5) and upper (6) plates has a groove (12) in which is positioned the deformable seal (4).