EP0737273B1 - Micropump - Google Patents

Description

The present invention relates to a micropump comprising at least one base plate, at least one plate upper and an intermediate insert between the two other plates and made up of one material capable of being machined so as to define a pumping chamber, at least one inlet control member fluid to connect the pumping chamber with at minus one inlet of the micropump, and at least one organ fluid outlet control to connect the pumping with at least one micropump outlet, the pumping chamber comprising a movable wall machined in the intermediate plate which can be moved in two opposite directions when aspirating a fluid from entering the pumping chamber or during expulsion of this fluid from the pumping chamber to the outlet, actuation means being provided for moving said movable wall to cause periodic variation of the volume of the pumping chamber, of the second elements being intended to limit the movement of expulsion fluid from the pumping chamber.

We know a micropump of this type from the document EP 0.392.978 which corresponds to the most prior art close. The intermediate plate of the micropump described in this document includes a stop limiting movement during the expulsion of the fluid. A piezoelectric chip is fixed on the opposite side of the plate intermediate and intended to move the latter. The suction movement of this intermediate plate is therefore also produced by the piezoelectric chip, but the amplitude of this movement cannot be precisely controlled. Because of this, the volume of subtance pumped with each reciprocating movement of the insert intermediate is not precisely defined and may vary depending on the performance and aging of the tablet piezoelectric.

Pumps of this type can be used in particular for in situ drug administration, miniaturization of the pump allowing a patient to wear it on oneself, or even possibly to receive a pump directly implanted in the body. Furthermore, such pumps allow dosing of small amounts of fluid to inject.

In an article titled "A piezoelectric micropump based on micromachining of silicon "published in" Sensors and Actuators "No 15 (1988), pages 153 to 167, H. Van Lintel and al. give a description of two embodiments of a micropump, each comprising a stack of three wafers, i.e. one silicon wafer machined placed between two glass plates.

The silicon wafer is etched to form a cavity, which with one of the glass plates defines the pumping chamber, an inlet or suction valve and at least one outlet or discharge valve putting the pumping chamber in communication respectively with a input channel and an output channel. The part of the plate forming a wall of the pumping chamber can be deformed by a control element constituted by example by a pellet or a piezoelectric crystal. This is equipped with two electrodes which, when they are connected to a source of electrical voltage, cause the deformation of the pellet and, consequently, the deformation of the wafer, which causes variation the volume of the pumping chamber. This movable wall or deformable of the pumping chamber can thus be moved between two positions.

The operation of the micropump is as follows. When no electrical voltage is applied to the piezoelectric pellet, inlet and outlet valves are in the closed position. When an electrical voltage is applied there is an increase in pressure in the pumping chamber which causes the opening of the outlet valve. The fluid contained in the pumping is then pumped back to the outlet channel by the displacement of the deformable wall from a first position to a second position. During this phase, the valve inlet is kept closed by the pressure prevailing in the pumping chamber.

On the contrary, when we decrease the tension electric, the pressure in the pumping chamber decreases. This closes the discharge valve and opening the inlet valve. Then there is aspiration fluid in the pumping chamber through the inlet channel as a result of the displacement of the deformable wall of the second position to the first position.

As already mentioned, these micropumps are used especially for the administration of drugs. he it is therefore important that the flow rate of the micropump is good determined, so that the drug to be injected is very precisely dosed. Now, the known micropumps present certain imperfections on this point.

Indeed, the flow rate of the micropump depends on the variation volume of the pumping chamber between the two deformable wall positions. This variation of volume depends on several parameters, among which the electrical voltage applied to the piezoelectric chip and the physical characteristics of the piezoelectric chip (thickness, diameter, dielectric constant) and of the deformable wall (material, thickness). So a same voltage applied to micropumps apparently identical may cause different deformations pumping chambers for these micropumps which, therefore, will have different flow rates.

Furthermore, for the same micropump, the flow rate may evolve over time due to the aging of materials of the piezoelectric pad and glue with which is fixed. Finally, the flow rate of the micropump depends on the pressure in the outlet channels and entry.

H. Van Lintel et al. have described in the article already cited a micropump with an additional valve which makes the flow less dependent on pressure in the outlet channel. However, this micropump does not not solve the other drawbacks mentioned upper.

The invention aims to solve the drawbacks mentioned and to obtain a micropump whose flow is very precise and constant, independent of variations in the performance and aging of the motor element and independent of pressures in the inlet pipe or Release.

The invention is characterized for this purpose, in that the micropump includes first stop elements limiting the suction movement of the fluid in the chamber pumping, the first and second stop elements being arranged so as to define the range of motion of the movable wall in the two opposite directions.

By limiting the range of motion in the two opposite directions, the volume of substance pumped at each reciprocating movement of the movable wall or membrane of pumping is clearly defined and remains constant. It does depend no variations in organ performance motor which is preferably a piezoelectric chip. Aging or other deterioration of this pellet piezoelectric does not influence the flow of substance pumped. It is therefore not necessary to provide a performance compensation circuit based on time in the control of the micropump.

Calibration of the micropump according to variations performance of the piezoelectric chip used is also not necessary.

The flow rate of the pumped substance is also appreciably independent of the pressure prevailing in the duct entry and exit. It only depends on the machining micropump and pumping frequency.

According to an advantageous variant, the movable wall comprises a rigid central part surrounded by a border thinner elastic coming from a piece with the rigid central part, the latter projecting with respect to the face of the movable wall which is opposite to the pumping chamber and intended to come into contact with the plate which is arranged opposite it to constitute said first abutment elements limiting the fluid suction movement of the movable wall.

The rigid central part of the movable wall ensures precise movement of this wall, comparable to movement of a piston. Pressure differences in the chamber only a small change in volume thanks to the smaller area of the elastic border surrounding the rigid central part.

According to a preferred mode, the actuation means comprise a drive member movably mounted on one base or top pads and an intermediate piece disposed between the movable wall and the drive member.

Advantageously, the drive member is mounted so movable on the outer face of said upper plate, said intermediate piece passing through the wafer upper by an opening.

Considering that the driving organ, preferably a piezoelectric chip, is not directly bonded to the membrane, variations in shape and in deformation of the piezoelectric chip have no influence on the shape of the deformable wall, so on the debit.

According to an advantageous variant, the movable wall is constituted by a membrane having a central part projecting so as to constitute with the plate upper said first stop elements, this part central being surrounded by a piezoelectric element attached to the membrane and having a central bore allowing the passage of the central room.

This arrangement allows a simple construction, everything by obtaining a double limitation of the movements of the deformable wall.

Finally, according to another favorable variant, the first stop elements consist of an adjustable screw crossing the upper plate and one end of which is arranged opposite the movable wall.

In this type of micropump, the volume of substance pumped with each reciprocating movement of the movable wall, therefore the flow rate can be adjusted by acting on one of the elements stop formed by the screw.

Other advantages emerge from the characteristics expressed in dependent claims and description setting out the invention below in more detail at using drawings which represent schematically and at As an example, three embodiments and a variant.

FIG. 1 illustrates a first embodiment of the invention in section along line I-I of FIG. 2.

Figure 2 is a horizontal sectional view along the line II-II of figure 1.

FIG. 3 represents a second embodiment of the invention in section according to FIG. III-III of the figure 4.

Figure 4 is a horizontal sectional view along the line III-III of Figure 3.

FIG. 5 represents a third embodiment of the invention in section along the line V-V in FIG. 6.

Figure 6 is a horizontal sectional view along the line VI-VI of figure 5.

Figure 7 illustrates a variant of the first mode of execution.

In these figures, the same element represented on several figures is designated on each of these by the same reference number. In the embodiments which will be described, the micropump is equipped with a valve inlet and outlet valve. It is right to note however that the invention also applies to micropumps comprising several valves arranged between the inlet and the pumping chamber and / or several valves arranged between the pumping chamber and the outlet. The micropump can also be provided with a plurality of inputs and a plurality of outputs. The inlet valves and output may be replaced by any other body fluid inlet or outlet control, such as flow limiters.

It should be noted that, for the sake of clarity, the thicknesses various platelets making up the micropump have were greatly exaggerated in the drawings.

Referring to Figures 1 and 2, the micropump according to the first embodiment comprises a basic plate 2, preferably in glass. This base plate 2 is breakthrough of a channel 4 forming the outlet duct of the pump. This conduit can for example be connected to a needle injection (not shown).

The base plate 2 is surmounted by a plate intermediate 6 made of silicon or another machinable material by etching using photolithographic techniques. It is attached to the base plate 2 by known bonding techniques, such as the technique known by the English term "anodic bonding" or welding anodic with heating to around 300 ° C and applying a potential difference of around 500V between the pads.

An upper plate 8, preferably made of glass, is joined by the same techniques to the intermediate plate 6. It is pierced with an inlet channel 10 which can be connected to a tank not shown in which is the liquid substance to be pumped, for example a drug to be administered with a precise dosage. In this application, the micropump can be worn on the body of the patient, or even be implanted.

By way of example, the intermediate silicon wafer 6 can have a crystal orientation <100>, in order to lend itself successfully to etching. The inserts 2, 6 and 8 are preferably carefully polished. These plates, 2,6 and 8 are then advantageously made hydrophilic, in particular in the case where the substance used in the micropump is an aqueous solution. To this end, the silicon wafer 6 can be immersed in boiling HNO ₃ .

To fix the ideas, the thicknesses of the plates 2, 6 and 8 can be approximately 1mm, 0.3mm and 0.8mm for a surface dimension of the pads around 10 by 20mm.

The inlet or suction 10 and outlet ducts or backflow 4 are mainly connected by a first inlet valve 12, a pumping chamber 50 and a second outlet valve 28.

The first valve 12 is of the machined non-return type in the silicon wafer 6 and formed by a membrane 14 of generally circular shape carrying an annular rib 16. The latter separates two compartments 18.20 provided on the upper part of the membrane 14 and cooperates, for this purpose, with the lower surface of the plate upper 8.

The first compartment 18 is in annular form and in communication with the inlet duct 10. The second compartment 20 occupies a substantially central position. It communicates via an orifice 22 slightly off center with a third compartment 24 located under the membrane 14.

The rib 16 is coated with a thin layer of oxide 26 also obtained by photolithography techniques and gives the membrane 14 a prestress or pretension stressing the top of the rib 16 against the plate upper glass 8 which serves as a valve seat.

Of course, other known types of valves or further flow limiters may be used at the place of the valve described.

The outlet valve 28 is also machined in the silicon wafer 6 and has a membrane 30 carrying an annular rib 32 coated with an oxide layer 34 giving the membrane 30 a preload stressing the top of the rib 32 against the lower plate 2 which serves as a valve seat. Oxide layers 33 applied on the other side of the membrane 30 reinforce this prestress.

The rib 32 defines a fourth behavior 36 communicating with outlet conduit 4 and a fifth compartment 38 outside the substantially shaped rib annular. A sixth compartment 40 is located above of the membrane 30 and is in communication with the outside of the pump through an opening 42. Electrical contacts or electrodes 44,46 are arranged opposite one another on the upper plate 8 and on a projecting part 48 of the membrane 30. These contacts allow an adequate control of the expulsion fluid. It is understood that other types known valves or flow limiters may replace the outlet valve 28.

The pumping chamber 50 is substantially shaped circular and connected by two passages 52 and 54 on the one hand to the third compartment 24 of the first valve 12 and on the other hand to the fifth compartment 38 of the second valve 28. The pumping membrane 56 constituting a wall movable or deformable of the pumping chamber 50 is machined in the silicon wafer 6 and has a part rigid central 58 relatively wide compared to the total width of the pumping membrane 56. The diameter of this central part 58 varies between 20 and 90% of the diameter pumping membrane 56, preferably between 50 and 80%. This rigid central part 58 includes a thickness significantly greater than the annular edge 61 of the pumping membrane. To fix ideas, the edge 61 has a thickness between 10 and 100 μm, while the rigid central part 58 has a thickness which is 10 to 50 µm less than the total thickness of the plate 6, which gives for example a thickness of 300 µm.

The pumping membrane 56 has on its lower surface facing the base plate 2, elements of stop 60, which are for example three in number. These stop elements 60 protrude from the bottom surface membrane and can consist of a silicon oxide layer. They are intended to come into contact with the upper surface of the base plate 2 to limit the movement of expulsion or repression of the pumping membrane 56. Similarly, the central part rigid 56 thicker is intended to come into contact with the upper plate 8, when the membrane of pumping 56 is actuated, to form elements of stop opposite the stop elements 60 in order to limit the suction movement of the pumping membrane 56. So the movement of the latter is mechanically controlled from the upper and lower side. This provides a very precise quantity of substance pumped at each round trip of the membrane. The central part rigid 56 is comparable to a piston whose movement is well defined. Since the annular edge 61 of the pumping membrane 56 has a relatively surface small compared to the total surface area of the membrane pumping 56, pressure differences in the pressure chamber pumping 50 generate only a small change in volume under the pumping membrane 56.

In addition, the oxide abutment elements 60 avoid a sticking or suction effect of the pumping membrane 56, when the latter moves from its position the lower up.

Electrical contacts or electrodes 62,64 are arranged facing each other on the central part rigid 58 and on the lower surface of the upper plate 8. These contacts 62,64 are extended outwards of the pump through an opening 66 and connected to a electrical circuit not shown to control the operation of the pumping membrane 56 and suction fluid. Adequate circuits are for example described in European patent application No. 0.498.863. In the described embodiment, these are more precisely these electrical contacts which form the stop elements limiting the suction movement of the pumping membrane 56.

The latter also comprises on both sides of the zones 65 covered with silicon oxide. These areas oxide 65 gives the membrane a certain prestress (not shown) up in Figure 1.

An actuating device 70 of the pumping membrane 56 includes a drive member in the form of a pellet piezoelectric 72 provided with connected 74.76 electrodes on a generator 78 intended to supply a voltage alternative. This tablet can be the one sold by the company Philips under the name PXE-52. She is fixed by any suitable means such as gluing or welding, on an elastic blade 80 made of metal, silicon or made of plastic. This blade 80 is mounted via a spacer 82 on the plate upper 8. This spacer 82 may be consisting of a plastic, metallic washer or silicon. It could also be formed by a predetermined thickness of glue or glass of a part with the plate 8. When gluing the elastic blade 80 on the upper plate 8, tension can be applied to the pad electrodes piezoelectric 72 so that the latter curves down towards the upper plate 8 during hardening of the glue. An intermediate piece 84 in the form of a pushpin can be made integral by its flat head 86 by any suitable means, such as gluing or welding, of the elastic blade 82. It acts on the part rigid central unit 58 of the pumping membrane 56 thanks to its vertical rod 88 passing through the upper plate by a hole 89. There may also be a slight clearance between the vertical rod 88 and the pumping membrane 56, when the pump is at rest. This game or a constraint mechanical between rod 88 and pumping membrane 56 can be determined by the curvature during hardening glue.

The actuating device 70 comprising a tablet piezoelectric 72 and an elastic blade 80, can also be replaced by a device comprising two or several adjacent piezoelectric plates or combined piezoceramic and metallic discs.

Thus, the piezoelectric pad 72 is independent of the pumping membrane 56. Hysteresis effects of the piezoelectric disc 72 ("piezocreep") or variations or deterioration of this tablet has not influence on the shape of the pumping membrane 56 considering that the latter is independent of the pellet piezoelectric 72 and set in motion thanks to the intermediate piece 84. This construction makes it possible to obtain a large volume of fluid displaced for a diameter given the pumping membrane, considering that the part rigid central unit 58 acts like a piston. The parts machined from the micropump can be further miniaturized while retaining an actuation device of any size, relatively large. This miniaturization of the machined parts makes it possible to lower the production costs.

The general mode of operation of this pump is similar to that described in the article by H. van Lintel et al. entitled: "A piezoelectric micropump based on micromachining of silicon "published in" Sensor and Actuators " No 15 (1988) pages 153 to 167.

Compared to this type of known micropump, the micropump according to the present invention therefore allows obtain a very precise dosage with each reciprocating movement, a dosage which is practically independent of the pressure prevailing in the inlet and outlet pipes, and a dosage which is practically independent of performance of the piezoelectric chip and damage and hysteresis phenomena known for this kind of actuating device. In addition, the movement of the pumping membrane is precisely controlled as much by the rigid intermediate piece 58 that the stops 60. The flow is therefore defined by the machining characteristics of the pumping membrane 56 and by the frequency of the device actuation.

This type of pump allows the use of piezoelectric pads having fairly wide variations in their characteristics. In addition, there is no need to calibrate the pumps for each tablet used.

Due to the external fixing of the patch, the latter can be easily replaced in the event of a defect.

Up to a certain pumping frequency, the flow is independent of viscosity. Thanks to the central part rigid and with electrical contacts 62.64, it is possible to detect the end of the fluid suction and to obtain additional information relating to the micropump operation.

It is understood that the embodiment described above has no limiting nature and that it may receive any desirable changes within the framework as defined by claim 1. In particular, the arrangement of valves and outlet ducts and inlet, as well as the pumping room can to be very different. The distribution of oxide zones can be adapted to the desired prestresses for the valves and pumping. The actuation device may present a motor member of a type other than a pellet piezoelectric.

Intermediate piece 84 could have come from a piece with elastic blade 80 or with the pad piezoelectric. It could also be freely disposed between the elastic blade and the pumping membrane.

The abutment elements 60 proper could to lack. The pumping chamber would then have a low height such as the upper surface of the insert base 2 serves as a stop element against which the pumping membrane 56 abuts each reciprocating movement. The control electrodes 44,46 and / or 62,64 could be constituted differently or be deleted in a simplified variant.

In accordance with FIG. 7, the pump can also present one or more screws 90 passing through the plate 8 and cooperating at their ends with the central part rigid 58 or with electrical contact 62. These screws 90 thus constitute adjustable stop elements allowing to adjust the amplitude of the suction movement. The contact 64 of figure 1 will then be replaced by the screw 90 in metallic material.

Adjustment screws can also be mounted on blade 80. In addition, it would be possible to mount screws adjustment in the flat head 86 of the intermediate piece.

The second embodiment illustrated in Figures 3 and 4 differs from the first embodiment only by the constitution of the pumping chamber and device actuation. As a result, elements analogous to two execution modes have the same reference numbers and will no longer be described in detail.

This second embodiment also includes a plate base 2 and an upper plate 8 pierced with inlet conduits 10, respectively outlet 4. Between these plates 2 and 8 is interposed the intermediate plate 6 in silicon machined by photolitographic techniques to obtain an inlet and outlet valve 12 28 and a pumping chamber 50.

Thin oxide layers 26,33,34 allow to obtain predetermined prestresses in the membrane in silicon.

The pumping chamber 50 is substantially shaped circular and connected by two passages 52 and 54 to the valves entry and exit. Machined in the insert silicon 6, the pumping membrane 156 in the form of a movable, deformable wall includes a central part rigid 158 thicker to form a stop element intended to cooperate with the lower surface of the wafer upper 8 in order to limit the suction movement of the pumping membrane 156. The latter has on its lower surface a lower stop element central 160. Preferably, this element limiting movement pumping membrane expulsion consists by a small extra thickness in silicon or by a layer silicon oxide. So the movement of the membrane of pumping 156 is stopped precisely on both sides up and down. This provides a exact amount of substance pumped on each round trip of the pumping membrane.

The actuating device 170 is constituted by a piezoelectric chip 172 having a central hole 173. The patch is fixed by welding or gluing to the pumping membrane 156. Electrical contacts 174,176 allow connection of the patch to a generator 78 intended to supply an alternating voltage.

Electrodes 162,164 are arranged opposite one of the other on the central part 158 and on the lower surface of the upper plate 8. These electrodes are extended to the outside of the pump by an opening 166 and make it possible to control the aspiration of the fluid and the operation of the pumping membrane 156. This the latter can also be provided with zones with silicon oxides 65 allowing to induce a certain prestress in the silicon membrane.

This type of construction with stop elements 160 and 158 exactly limit the movement of the diaphragm pumping 156 in two opposite directions allows also a precise dosage of the amount of substance pumped with each reciprocating movement. The pumping rate depends only on the machining characteristics of the pumping membrane and the frequency of the actuating device. Variations or deterioration in performance of the piezoelectric chip in some limits do not influence the flow rate of the micropump. he there is no need to calibrate the micropump, an assembly precise is enough. The construction of this mode of execution is simpler than that of the first embodiment.

The third embodiment represents in FIGS. 5 and 6 also differs from the first and second embodiment mainly by the constitution of the membrane of pumping and actuation device. As a result, elements similar to the three embodiments carry the same reference figures and will no longer be described from in detail.

This third embodiment also includes a base plate 2 and upper plate 8 provided of inlet conduits 10, respectively of outlet 4. Between these plates 2 and 8 is interposed the intermediate plate 6 made of silicon machined by photolithographic techniques to obtain an inlet valve 12 and outlet 28 and a pumping chamber 50. Thin layers 26,33,34,65 oxide allow to obtain prestressing predetermined in the silicon membrane.

The pumping chamber is also circular in shape and connected by passages 52 and 54 to the valves entry and exit. Machined in silicon wafer 6, the pumping membrane 256, in the form of a wall of the pumping chamber, has a thickness substantially uniform and has on its lower surface a lower stop element 260 to limit the eviction movement. Preferably, this stop element consists of a small silicon area or made of silicon oxide. It is placed under the device actuator comprising a piezoelectric pad 270 fixed by welding or gluing on the upper surface of the pumping membrane 256 and connected by connections 274,276 to a generator 78 intended to supply a voltage alternative.

A member with an adjustable upper stop 258 intended for limit the suction movement consists of a annular part 261 inserted and fixed by gluing in a bore of the upper plate 8. This annular part 261 has a threaded bore 263 capable of receive a screw 265 which forms the adjustable stop in height intended to cooperate with the piezoelectric pad 270. The annular part 261 and the screw 265 are of preferably in metallic material.

Thus, the movement of the pumping membrane 256 is precisely limited up and down. In addition, it is possible to adjust the amplitude of this movement by acting on the screw 265. This construction therefore allows to obtain a very precise quantity of pumped substance at every reciprocating movement of the pumping membrane all by authorizing an adjustment of the pumped quantity. Variations or deterioration of the performance of the tablet piezoelectric within certain limits do not influence not the flow rate of the micropump. An electrical contact 264 provided on the metal screw 265 allows, together with the upper connection 276 of the piezoelectric pad, to control the fluid suction movement of the pumping membrane 256.

Advantageously, the screw 265 may be made up of a material capable of compensating for variations in shape of the movable wall 256 due to temperature effects, because such variations without compensation can influence the volume of the pumped fluid. Such compensation could also be obtained using the 90 screws described with reference to Figure 7.

The modes of execution described are particularly adapted for administering medicaments in the form of micropumps capable of being implanted in the body of a patient.

Claims (14)

1. A micropump including at least one base plate (2), at least one upper plate (8) and an intermediate plate sandwiched between the two other plates (2, 8) and made of a material capable of being machined in such a manner as to define a pumping chamber (50), at least, one control member (12) for controlling the inflow of fluid from, at least, one inlet (10) of the micropump to the pumping chamber and, at least, one control member (28) for controlling the outflow of fluid from the pumping chamber (50) to, at least, one outlet (4) of the micropump, the pumping chamber (50) having a movable wall (56, 156, 256) machined in the intermediate plate (6) and capable of being moved in two opposite directions during the suction of a fluid at the inlet (10) into the pumping chamber (50) or during the expelling of this fluid from the pumping chamber, towards the outlet (4), actuation means (70, 170, 270) being provided for displacing said movable wall (56, 156, 256) to produce a periodical variation of the volume of the pumping chamber (50), second stop members (2, 60; 2, 160; 2, 260) being provided for limiting the motion producing the expelling of the fluid from the pumping chamber (50), characterized in that the micropump includes first stop members (58, 62, 64; 158, 162, 164; 258, 270) limiting the motion producing the suction of the fluid into the pumping chamber (50), the first and second stop members being arranged so as to limit the amplitude of the motion of the movable wall (56, 156, 256) in the two opposite directions.
2. A micropump according to claim 1, characterized in that the movable wall (56) includes a central rigid part (58), surrounded by a resilient edge of a lesser thickness (61), integral with the central rigid part (58), the latter protruding with respect to the face of the movable wall (56) which is opposite from the pumping chamber (50) and being designed for coming in contact with the plate (2, 8) which is facing it to provide said first stop members limiting the motion of the movable wall (56) during the suction of the fluid.
3. A micropump according to claim 2, characterized in that the width of said central rigid part (58) is in the range from 20 to 90% of the width of the movable wall (56) and, preferably, from 50 to 80%.
4. A micropump according to claim 1, characterized in that the face of the movable wall (56), which is directed towards the inside of the pumping chamber (50), includes one or several elevations (60, 160, 260) providing, along with the facing plate (2), the second stop members limiting the motion producing the expelling of the fluid.
5. A micropump according to one of claims 1 to 4, characterized in that the actuation means (70) include a driving member (72) mounted movably on one of the base or upper plates (2, 8) and an intermediate piece (84) disposed between the movable wall (56) and the driving member (72).
6. A micropump according to claim 5, characterized in that the driving member (72) is mounted movably on the outer face of said upper plate (8), said intermediate piece (84) extending through the upper plate (8) via an opening (89).
7. A micropump according to claim 6, characterized in that the driving member is a piezoelectric member (72, 80) which is mounted via a spacer member (82) on the outer face of the upper plate (8).
8. A micropump according to claim 6 or 7, characterized in that the intermediate piece (84) includes a flat head (86) integral with the piezoelectric member (72, 80) and a rod (88), extending through the upper plate (8) and acting through its end on the movable wall (56).
9. A micropump according to claim 1, characterized in that it includes electrodes (62, 64; 162, 164; 262, 264) placed facing each other on the movable wall (56; 156; 256) and on the upper plate (8), these electrodes being connected to a circuit capable of controlling the functioning of the deformable wall (56; 156; 256).
10. A micropump according to claim 1, characterized in that the movable wall (156) is comprised of a membrane exhibiting a central piece (158) protruding so as to form with the upper plate (8) said first stop members, this central piece being surrounded by a piezoelectric member (172) affixed to the membrane and exhibiting a central bore (173) allowing the passage of the central piece (158).
11. A micropump according to claim 1, characterized in that the first stop members are comprised of an adjustable screw (90, 265) extending through the upper plate (8) and of which one end is positioned facing the movable wall (56, 256).
12. A micropump according to claim 11, characterized in that a piezoelectric member (270) is sandwiched between said end of the screw (265) and the movable wall (256) and is made integral with the latter.
13. A micropump according to claim 11 or 12, characterized in that the screw or screws (90, 265) are made of a material capable of compensating the variations of the shape of the movable wall (56, 256) caused by temperature effects.
14. A micropump according to one of claims 1 to 13, characterized in that it includes second electrodes (44, 46) placed facing each other, one (44) of these second electrodes being mounted on a movable wall disposed downstream of the pumping chamber (50), so as to control the expelling of the fluid from the micropump.

Images