EP0956449B1 - Microejection pump - Google Patents

Abstract

The pump for generating microdrops consist of at least one pump chamber designed in a silicon chip and a silicon membrane located above the chamber that can be operated piezoelectrically. The pump chamber is connected to at least one feed channel and one outlet channel provided with a discharge opening and has a glass chip to seal off the chamber opposite the silicon membrane. The feed channel found in the silicon chip (2) in the direction of the pump chamber is designed at least partly as a diffusor element and the outlet channel opens out in an exit plane.

Description

The invention relates to a micro ejection pump for generation of microdroplets consisting of at least one in one Silicon chip-formed pump chamber, one above the pump chamber arranged and piezoelectrically actuable silicon membrane, wherein the pump chamber with at least one inlet channel and an exhaust port provided with an exhaust port is connected and in which a glass chip opposite the silicon membrane at least closes the pump chamber.

With the help of such micro ejection pumps the handling allows the smallest amounts of liquid, both pure Substances or mixtures of substances can be, or also in liquids Suspended microparticles contained in the chemical Analytics, medical technology, biotechnology etc., targeted further processing.

These micro ejection pumps allow in connection with a suitable handling device, e.g. Manipulators that targeted delivery of these substances to the site of sample processing or a sample waste. With the help of a appropriate positioning technology can take sampling and Sample storage location may be different.

This sample storage location can be a liquid surface, a Solid surface or a gas-filled reaction chamber his.

A micropump intended for the above applications is from the US 50 94 594 A become known. This micropump consists of a pump unit with an associated pump chamber and a deformable chamber segment on which an electrically controllable Piezo element is arranged. The liquid to be pumped the pump chamber via an inlet capillary (inlet channel) fed. By actuating the piezo element alternately exerted on the deformable chamber segment Force causes a constant change in pressure in the pump chamber, see above that alternately loading them via the inlet capillary and expelling the liquid via one with the pumping chamber related outlet capillary.

In order to achieve a sufficient pumping effect, the Inlet and the outlet capillary each piezoelectrically actuable Valves provided.

The manufacture of such a micropump in the silicon substrate can with the help of the known photolithographic process and the anisotropic structure etching. On the silicon substrate structured in this way is then through anodic bonding applied a glass plate and so a solid glass-silicon composite created.

With such a micropump it is possible to use small amounts of liquid to apply, but a relatively limited Frequency range and thus also a limited one Funding rate is available. With the one described above Micropump can, for example, a delivery rate of reach about 500 picoliters. To ensure the necessary Functional reliability of this micropump, it is necessary that the liquids or suspensions are as low as possible Have viscosity.

Furthermore, a micropump can be seen from WO, A, 9419609, which a pump chamber with variable chamber volume and contains a liquid inlet and a liquid outlet. In order to transport liquid through the pump chamber to reach towards the liquid outlet and at the same time on the otherwise necessary valves subject to wear To do without is a combination of a diffuser provided with a nozzle. The diffuser here is the liquid inlet and the nozzle associated with the liquid outlet.

The generation of individual microdroplets with a defined droplet volume is not possible with this micropump.

The invention has for its object a micro ejection pump to create the handling of liquids or Suspensions, or of liquefiable substances, in the volume range from a few picoliters to a few hundred Microliters, which has a high frequency stability and with which the generation of individually countable, directed, accelerated and impulsive defined their drop volume and reproducible microdrops is possible.

According to the invention, the task in a micro ejection pump of the type mentioned in that the silicon chip located inlet channel towards the pumping chamber at least partially as a diffuser element with an opening angle is formed to 10 ° and that the outlet channel as Microcapillary is formed with an outlet in an exit level opens.

By inserting the diffuser element according to the invention the pumping chamber becomes the frequency stability of the microejection pump significantly improved. The anisotropy of the diffuser flow resistance supports drop formation in pump mode, i.e. there is a jet effect along the positive Pressure drop and in loading mode is the liquid afterflow into the pumping chamber, i.e. there is a diffuser effect along the positive pressure gradient. Furthermore becomes the generation through the diffuser effect in loading mode of air bubbles in the pump chamber at high frequencies suppressed. This way extremely high Delivery rates up to approx. 750 µl / min at an excitation frequency up to approx. 6500 Hz. When using the invention Micro ejection pump for printing can by the Diffuser a higher printing speed can be achieved.

The outlet channel is also designed as a microcapillary, so that the sample delivery in the form of individually countable, directed, accelerated with impulses and in terms of their Drop volume of defined microdroplets is reproducible. The volume of the drops and the delivery rate are through the electrical parameters (frequency, amplitude, pulse shape) the pump control adjustable.

The best effect is achieved when the diffuser element Pump chamber is arranged immediately, or immediately extends to the pumping chamber, the diffuser element in a first variant of the invention a constant opening angle having.

The opening angle of the diffuser element should preferably be 3 - 5 °.

In a second variant of the invention, the diffuser element has a constantly changing opening angle. The For example, the opening angle can increase continuously.

In a further embodiment of the invention, the pump chamber a floor plan with straight or curved boundary lines on, with the diffuser element in an entrance zone the pump chamber opens. In addition, the microcapillary is between the pumping chamber and the discharge opening can be connected to further inlet channels. This makes it possible for the pumped through the pumping chamber Add liquid to other substances in a targeted manner.

The micro ejection pump preferably consists of a composite from a micromechanically structured silicon chip and a glass chip.

To avoid unnecessary contamination, the micro ejection pump, i.e. the combination of the silicon chip and the Glass chip, in the direction of the discharge opening of the outlet duct in tapered x and / or y direction. This ensures that when immersing the micro ejection pump in a liquid has very little surface contamination takes place, which then takes place in one cleaning step can be easily removed accordingly. So that can can be prevented in a simple manner that substances unintentionally and can be carried away unnoticed. The invention Micro ejection pump is therefore also for manipulation smallest amounts of liquid particularly suitable.

The taper in the x direction can be advantageous during the sawing of the silicon chip are formed, whereas the taper in the y direction during the anisotropic Structure etching can be formed.

Of course, it is also possible to make the tapering later through a final grinding process.

In a further embodiment of the invention, the silicon chip heated directly and temperature-controlled, i.e. it will the ohmic resistance of the silicon is exploited by the Heating effect due to Joule heat generated in the silicon material becomes.

The heater is preferably integrated in the silicon membrane, or acts directly on them, the electrical contacts arranged laterally opposite on the silicon chip are.

Through the inventive development of the invention with the At least on the heating acting on the pump chamber are the possible uses in connection with the invention Arrangement of the diffuser element expanded considerably without that additional design changes to the microejection pump itself, e.g. in terms of dimensioning would. In addition, it is possible by heating up a quick and easy way to dry the outside Micro ejection pump.

In addition, it is now possible to use even highly viscous liquids, those with low viscosity when exposed to heat, i.e. liquid are going to handle. Such liquids can e.g. containing glucose or be oily substances that are then exploited the advantages of the diffuser element are promoted can.

If the heating is designed accordingly, even melted ones can be used Metals, e.g. Tin or tin-lead alloys, or other substances that are otherwise due to their viscosity in the Micro ejection pump are not eligible, easily promoted become. These substances can then be thermally activated promoted and also printed.

In a further continuation of the invention is on the Silicon chip a temperature sensor with an associated Control circuit arranged. With this it is possible to connect with a suitable flow meter all parameters to regulate the micro ejection pump electrically so that it is lossless precisely defined amounts of liquid are dispensed can.

The electrical contacts and the temperature sensor should be off a chemically neutral material, with photolithography structured platinum or tantalum layers for this are particularly suitable.

A particularly advantageous continuation of the invention is through a parallel arrangement of several pumping chambers an associated inlet diffuser and outlet channels.

This makes an extremely powerful micro ejection pump created with which you can work in parallel is possible, or where the pumping chambers are controlled separately become. The latter variant allows at the same time or in time staggered different materials or liquids handle.

In the parallel arrangement, it is appropriate to between the individual outlet channels each have an additional suction channel to provide, which also flows into the exit level. In order to is reliably prevented from emerging from an outlet escaping liquid through neighboring outlet openings can spread.

Fig. 1

eine schematisch im Schnitt dargestellte Draufsicht auf die Mikroejektionspumpe;

Fig. 2

eine im Schnitt dargestellte Seitenansicht der Mikroejektionspumpe nach Fig. 1;

Fig. 3

die Draufsicht auf die Mikroejektionspumpe nach Fig. 1 und 2;

Fig. 4

eine schematische Darstellung einer Variante der Mikroejektionspumpe mit runder Pumpkammer;

Fig. 5

eine Mikroejektionspumpe mit einem Mehrkanalsystem;

Fig. 6

eine Mikroejektionspumpe mit Verjüngungen in x-Richtung;

Fig. 7

eine Mikroejektionspumpe mit Verjüngungen in y-Richtung;

Fig. 8

die Rückansicht des Siliziumchips für eine Mikroejektionspumpe mit Temperatursensor und Steuerschaltung; und

Fig. 9

die Vorderansicht des Siliziumchips nach Fig. 8 mit ovaler Pumpkammer.

The invention will be explained in more detail using an exemplary embodiment. The individual drawing figures show:

Fig. 1

a schematically shown in section plan view of the micro ejection pump;

Fig. 2

a sectional side view of the micro ejection pump of FIG. 1;

Fig. 3

the top view of the micro ejection pump according to FIGS. 1 and 2;

Fig. 4

a schematic representation of a variant of the micro ejection pump with a round pump chamber;

Fig. 5

a micro-ejection pump with a multi-channel system;

Fig. 6

a micro ejection pump with tapering in the x direction;

Fig. 7

a micro ejection pump with tapering in the y direction;

Fig. 8

the rear view of the silicon chip for a micro ejection pump with temperature sensor and control circuit; and

Fig. 9

the front view of the silicon chip of FIG. 8 with an oval pump chamber.

The micro ejection pump 1 shown in FIGS. 1 to 3 consists of a composite of a silicon chip 2 and a Glass chip 3 connected by anodic bonding are. The silicon chip 2 is structured on two sides, wherein a flat one on the side opposite the glass chip 3 Pump chamber 4 is formed by a silicon membrane 5 is closed to the outside (Fig. 2). On this silicon membrane 5 is a piezoelectric plate actuator 6, for example attached by means of the known chip bonding technology. This plate actuator is used to deflect the Silicon membrane 5, so that the volume of the pump chamber 4 alternately is enlarged or reduced, which increases the pumping effect is achieved.

The control of the piezoelectric plate actuator 6 can by an electronic control, not shown predetermined frequency and amplitude. It did proved to be useful for the switch-on pulse high slope, i.e. a sudden switch-on pulse pretend. The subsequent switch-off pulse can be a damped one have a flat course, e.g. corresponding to an e-function. The pump behavior of the invention is thus Micro ejection pump further improved.

It is also expedient to use the piezoelectric plate actuator 6 with a bias voltage before the switch-on pulse apply. The bias should be the polarity of the Switching impulse be opposite. Through this in Loading mode available larger volumes of the pump chamber 4 will significantly improve the pumping performance of the Micro ejection pump 1 reached.

Furthermore, the pump chamber 4 with an inlet channel 7 and provided an outlet channel 8, the outlet channel 8 with an ejection opening 9 for ejecting individual microdroplets 10 is provided. The pump chamber 4 essentially has one square or rectangular plan, with the an inlet channel 7 in connected to a fluid inlet 16 (FIGS. 8, 9) an entrance zone of the pump chamber 4 opens. The outlet duct 8 is arranged on the opposite side of the pump chamber. In principle, the pump chamber 4 can also have a floor plan have curved boundary lines and, for example, round (Fig. 4), or also oval (Fig. 9).

The inlet channel 7 is designed as a diffuser element 11, i.e. the inlet channel 7, or part of the same widens in Direction to the pump chamber 4. The diffuser element 11 can be designed such that the opening angle over the entire length of the diffuser element 11 is constant. Of course it is also possible to use the diffuser element 11 in this way to design that the opening angle changes constantly. So the opening angle can be within predetermined limits also increase continuously (Fig. 9)

In principle, it is possible to use the microcapillary Outlet channel 8 between the pump chamber 4 and the discharge opening 9 to be connected to other inlet channels. In order to can the liquid pumped out of the pump chamber 4 other substances are added, which is the possible uses the micro ejection pump has been expanded considerably.

The equipment of the micro ejection pump 1 according to the invention the diffuser element 11 enables stable operation via a large frequency range, or the delivery rate over the excitation frequency for the plate actuator 6 is regulated be, with a particularly steep switch-on pulse and a flat switch-off pulse are particularly advantageous because the formation of gas bubbles in the pump chamber 4 also is prevented.

Another extension of the application possibilities for the Micro ejection pump enables heating to be integrated at least into the silicon membrane 5 of the silicon chip 2.

The micro ejection pump 1 can therefore not only be used for handling of liquids or suspensions with low viscosity are used, but also for such materials that with an increase in temperature low or low viscosity become. Another aspect of integrated heating is in it to see that this also results in a simple drying of the wetted Areas of the micro ejection pump 1 is made possible. For example can result in outer wetted areas of the micro ejection pump 1 can be dried quickly, causing a carryover of liquids can be safely prevented.

The integration of the heater can be done easily take place that the electrical resistance of the silicon chip 2nd is used directly for heating. These are for electrical Contacting electrical contacts 17, 18 provided which are laterally opposite on the silicon chip 2 extend (Fig. 8). In conjunction with one on the silicon chip 2 arranged temperature sensor 19 with associated Control circuit 20 can thus also be highly viscous per se Liquids or suspensions, such as oils, fats or Liquids containing glucose by the micro ejection pump 1 be promoted. If the heating is designed accordingly this way, even fusible metals can be extracted, so that the micro ejection pump 1 also for printing Metals such as tin or lead-tin alloys or others Is suitable.

Since the area of application of the micro ejection pump 1 is basically is not restricted, all parts must be filled with liquids can come into contact, be chemically neutral. Out for this reason it is advisable to have the electrical contacts 17, 18 and the temperature sensor 19 from a photolithographic structured platinum or tantalum layer.

To continue the wetted or contaminated surface of the micro ejection pump 1 when depositing liquids on or in Keep liquid surfaces as low as possible can, it is advantageous if the composite from the silicon chip 2 and the glass chip 3 towards the discharge opening 9 of the Outlet channel 8 is tapered in the x and / or y direction, such as this is shown in principle in FIGS. 6 to 9. That can in that the taper 14 in the x direction during of sawing the silicon chip 2 is formed. The Taper 15 in the y direction can be easily during the anisotropic structure etching of the semiconductor chip 2 form.

Of course, the taper 14; 15 also through a final grinding process are formed, wherein in this case also a taper of the glass chip 3 in the y direction can be manufactured.

Another way to keep this contamination to a minimum to be able to hold, is the immersion area of the Micro ejection pump 1 with a hydrophobic surface treatment to provide. This can be done by silanization or by coating e.g. with a layer that is a Teflon coating is similar. This layer of carbon and fluorine can be made using the plasma polymerization process getting produced. Generally speaking, however it should be noted that the internal channel and Chamber area of the micro ejection pump 1 not coated with becomes.

The advantages of the invention can be seen in the fact that Diffuser element 11 a significant improvement in frequency stability the micro ejection pump 1 is reached. The anisotropy the flow resistance of the diffuser element 11 supports the formation of the microdrops 10 in the pump mode, i.e. there is a nozzle effect along the positive pressure gradient. In the loading mode of the pump chamber 4, the liquid afterflow supported, i.e. there is a diffuser effect along the positive pressure gradient. Furthermore is the generation by the diffuser effect in loading mode of air bubbles in the pump chamber 4, especially at high ones Excitation frequencies of the plate actuator 6 effectively suppressed. So that the micro ejection pump 1 is large Frequency spectrum can be used and it can also be extremely high Delivery rates up to approx. 750 µl / min, with an excitation frequency up to approx. 6500 Hz.

With the help of the heating integrated in the silicon chip 2 as well the temperature sensor 19 with the associated control circuit 20 can the micro ejection pump 1 for any liquids, Suspensions also of higher viscosity and also meltable Metals and the like be used when these materials in a reasonable temperature range sufficiently low viscosity can be made. As already explained, a quick drying of wetted areas of the micro ejection pump 1 bring about.

The supply of the materials to be handled from a storage container to the pumping chamber 4 can be via conventional hose lines respectively.

The application of the design of the micro ejection pump according to the invention 1 with the diffuser element 11 is not on it limited that only one pump chamber 4 is present. It is easily possible to create micro ejection pumps, the one Parallel arrangement of pumping chambers 4 in connection with the Have diffuser elements 11 according to the invention (FIG. 5).

If this parallel arrangement is switched in parallel, one becomes extremely powerful micro ejection pump created. Also is a highly parallel work possible by the individual Pump chambers 4 can be controlled separately accordingly,

In the latter case, however, it is appropriate to move between the individual Outlet channels 9 each have a suction channel 21 to provide, which also opens into the exit plane 22. This allows the spread of liquid in the exit plane 22 and thus contamination of adjacent outlet openings 9 can be prevented safely.

The technological realization of the micro ejection pump according to the invention 1 can by the application of the known microtechnical Microforming take place and the connection of the Silicon chips 2 with the glass chip 3 using the anodic Bonding.

In a first preparation process, consisting of the sub-steps thermal oxidation, photolithography and anisotropic Structural etching is first the two-sided structure Silicon chip 2 manufactured. This silicon chip 2 receives the structures of a micro ejection pump 1 with the outlet channel 8, the pump chamber 4 with associated silicon membrane 5 and the inlet channel 7 with the diffuser element 11. The structured in this way Silicon chip 2 is used after a multi-stage cleaning a glass chip 3, consisting of a Pyrex 7740 glass plate, through anodic bonding to a solid silicon-glass composite together. The production of the parallel arrangement can done in the same manner as described above.

The thickness of the glass plate is, for example, 1 mm and the silicon membrane between 50 - 190 µm. The thickness of the piezoelectric Plate actuators 6 should be in the range of 100 - 260 µm.

LIST OF REFERENCE NUMBERS

1

microejection

2

silicon chip

3

glass chip

4

pumping chamber

5

silicon membrane

6

plate actuator

7

inlet channel

8th

outlet channel

9

discharging port

10

microdroplets

11

diffuser element

12

inlet channel

13

inlet channel

14

Taper in the x direction

15

Taper in the y direction

16

fluid inlet

17

Rontakt

18

Contact

19

temperature sensor

20

control circuit

21

suction

22

exit plane

Claims (18)

1. Microejection pump for the generation of microdrops, consisting of at least one pumping chamber formed in a silicon chip, of a silicon diaphragm arranged above the pumping chamber and capable of being actuated piezoelectrically, the pumping chamber being connected to at least one inflow duct and to an outlet duct provided with an ejection orifice, and in which a glass chip closes the pumping chamber in relation to the silicon diaphragm, the inflow and outflow duct (7, 8) being located on opposite sides of the pumping chamber (4), characterized in that the inflow duct (7) located in the silicon chip (2) is formed in the direction of the pumping chamber (4), at least partially, as a diffuser element (11) with an opening angle of up to 10°, and in that the outlet duct (8) is formed as a microcapillary which issues with an ejection orifice (9) in an outflow plane (22).
2. Microejection pump according to Claim 1, characterized in that the diffuser element (11) directly precedes the pumping chamber (4).
3. Microejection pump according to Claims 1 and 2, characterized in that the diffuser element (11) has a constant opening angle.
4. Microejection pump according to Claims 1 to 3, characterized in that the opening angle is preferably 3 - 5°.
5. Microejection pump according to Claims 1 to 3, characterized in that the diffuser element (11) has a continuously varying opening angle.
6. Microejection pump according to Claims 1 to 5, characterized in that the pumping chamber (4) has a base contour with straight or curved boundary lines.
7. Microejection pump according to Claims 1 to 6, characterized in that the outlet duct (8) is capable of being connected to further inflow ducts between the pumping chamber (4) and the ejection orifice (9).
8. Microejection pump according to Claims 1 to 7, characterized by a composite structure consisting of a micromechanically structured silicon chip (2) and of a glass chip (3).
9. Microejection pump according to Claim 8, characterized in that the composite structure consisting of the silicon chip (2) and of the glass chip (3) is narrowed in the direction of the ejection orifice (9) of the outlet duct (8) in the x- and/or y-direction.
10. Microejection pump according to Claim 9, characterized in that the narrowing (14) in the x-direction was formed during the cutting-out sawing of the silicon chip (2).
11. Microejection pump according to Claim 9,
    characterized in that the narrowing (15) in the y-direction was formed during the anisotropic structural etching.
12. Microejection pump according to Claim 9, characterized in that the narrowing (14; 15) was formed by means of a concluding grinding process.
13. Microejection pump according to one of Claims 1 to 12, characterized in that the silicon chip (2) is capable of being heated directly and in a temperature-regulated manner.
14. Microejection pump according to Claim 13, characterized in that the heating is integrated into the silicon diaphragm (5) of the silicon chip (2), and in that the electrical contacts (17, 18) are arranged laterally opposite one another on the silicon chip (2).
15. Microejection pump according to Claims 13 and 14, characterized in that a temperature sensor (19) with an associated control circuit (20) is arranged on the silicon chip (2).
16. Microejection pump according to Claims 13 to 15, characterized in that the electrical contacts (17, 18) and the temperature sensor (19) consist of a photolithographically structured platinum or tantalum layer.
17. Microejection pump according to Claims 1 to 16, characterized by a parallel arrangement of a plurality of pumping chambers (4), each with an inlet diffuser (11) and outlet ducts (8).
18. Microejection pump according to Claim 17, characterized in that suction extraction ducts (21) issue between the outlet ducts (8) in the outflow plane (22).

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