WO2003095837A1

WO2003095837A1 - Free jet dosing module and method for the production thereof

Info

Publication number: WO2003095837A1
Application number: PCT/EP2003/004754
Authority: WO
Inventors: Martin Wackerle; Martin Richter
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2002-05-07
Filing date: 2003-05-06
Publication date: 2003-11-20
Also published as: DE10220371A1; EP1488106A1; DE50303833D1; EP1488106B1

Abstract

A free jet dosing module comprises: a dosing chamber (78) having a dosing chamber volume; an actuating device (64, 68), which is adjoined to the dosing chamber (78) and which, when actuated, reduces the dosing chamber volume by a displacement volume, and; a discharge opening (80) that is fluidically connected to the dosing chamber (78). A nozzle volume is defined by a fluid area existing between the dosing chamber (78) and the discharge opening (80). The ratio of the displacement volume to the sum of the dosing chamber volume and the nozzle volume is greater than the ratio of a free jet pressure to the atmospheric pressure in order to produce a free jet even in the presence of a compressible gaseous medium that essentially fills the dosing chamber volume and the nozzle volume. The free jet pressure is the pressure, which is required inside the dosing chamber and which, for a given discharge opening surface, just suffices in order to generate the surface energy for effecting a free jet at the discharge opening. .

Description

Free jet metering module and method for its production

description

The following invention relates to a free jet metering module and a method for its production, and in particular to such a free jet metering module which is based on the principle of volumetric displacement.

Two principles for bubble-tolerant free jet metering modules are known from the prior art. The first principle works analogously to the ink jet principle, whereby a piezo actuator or a bubble, which is generated by a heating device, generates a pressure wave in a metering chamber, which propagates to a nozzle which is in fluid communication with the metering chamber and triggers drops there. Free jet metering modules of this type, which operate according to the ink jet principle, eject drops in the picoliter range, a typical drop size being 50 picoliters. The repetition frequency with which such a free jet metering module can be operated is a few kHz. Such free jet metering modules working on the ink jet principle are disadvantageous in that the volume of the drop ejected depends on the rheological properties of the liquid, for example the viscosity, the density or the surface tension thereof.

In addition, metering devices are known from the prior art which operate on the physical principle of volumetric displacement. In metering devices of this type, the metering volume of a metering chamber is displaced volumetrically by a micro actuator via a membrane. The typical volume of a jet ejected by such a displacement is 50 nanoliters. Such a system, which is based on volumetric displacement, is disadvantageous in that typical repetition frequencies may not exceed 10 to 20 Hz, since the capillary pressure at the nozzle must not be undercut when suctioning, since otherwise air would be sucked back into the metering chamber.

A general disadvantage of all known free jet metering modules is that they are not bubble-tolerant. In other words, an air bubble entering the metering chamber of the respective metering module causes the metering module to fail. The metering chamber with the liquid to be metered must therefore always be carried out completely, which is particularly difficult when the metering chamber has corners and the like. Furthermore, air bubbles can get into the dosing chamber by transport, by diffusion through the plastic hose connector, with which the metering module is connected, for example, to a reservoir, or by the outgassing of supersaturated liquids, for example, by temperature changes. Although it is known in part from the prior art to detect a failure of the metering module, for example by means of a stroboscopic function test or an optical bubble detection between the reservoir and the metering chamber, this always results in an interruption of the metering process and the metering module has to be refilled with great effort become.

A self-priming micromembrane pump that enables the delivery of compressible media is known from DE-A-19719862 The object of the present invention is to provide a bubble-tolerant free jet metering module and a method which is suitable for producing such a module.

This object is achieved by a free jet metering module according to claim 1 and a method according to claim 12.

The present invention provides a free jet metering module with the following features:

a dosing chamber with a dosing chamber volume;

an actuating device adjoining the metering chamber which, when actuated, reduces the metering chamber volume by a displacement volume; and

an ejection opening fluidly connected to the dosing chamber, a nozzle volume being defined by a fluid region existing between the dosing chamber and the ejection opening,

the ratio of the displacement volume and the sum of the metering chamber volume and the nozzle volume being greater than the ratio of a free jet pressure to the atmospheric pressure in order to generate a free jet at the discharge opening, even if a compressible gaseous medium which essentially filled the metering chamber volume and the nozzle volume were present, the Free jet pressure is the pressure required in the metering chamber which is just sufficient for a given discharge opening area to generate the surface energy in order to cause a free jet at the discharge opening. The present invention also provides a method for producing a free jet metering module, which has the following steps:

Providing a layer composite of a first layer and a second layer;

Etching at least one metering chamber structure and a nozzle structure fluidly connected to the same, reaching as far as the first layer in the second layer;

Connecting a third layer to the second layer to create a dosing chamber and a nozzle chamber; and

Thin the fourth layer to produce an actuator membrane adjacent to the dosing chamber.

The present invention is based on the finding that a free jet metering module can work reliably in a bubble-tolerant manner if its compression ratio, ie the ratio of displacement volume and the sum of metering chamber volume and nozzle volume, is chosen to be greater than the ratio of free jet pressure to atmospheric pressure. The free jet metering module according to the invention preferably consists of a metering chamber, a nozzle, a feed line and optionally a reservoir which is connected to the feed line, the module being designed in such a way that the ratio of the displaced volume of the actuating device and the dead volume, which results from the sum of the dead volume of the metering chamber and nozzle chamber is greater than the ratio of the pressure required to form a free jet to the atmospheric pressure. Preferred exemplary embodiments of the free jet metering module according to the invention comprise a valve element between the feed line and metering chamber and / or between the discharge opening of the nozzle and metering chamber. Such a valve element can be formed by a passive check valve, an active valve or a diffuser nozzle element. If a valve element is provided between the discharge opening of the nozzle and the metering chamber, this must be taken into account when determining the necessary compression ratio of the free jet metering module by making this compression ratio greater than the ratio of the sum of the free jet pressure and the pressure required to open the passive check valve to the atmospheric pressure , A filter element can be provided in the feed line to the nozzle chamber, a valve element preferably being arranged between the filter element and the nozzle chamber.

The method according to the invention is particularly suitable for producing a free jet metering module, the compression ratio of which satisfies the above condition. The method according to the invention manages with a small number of mask steps, at least two, in order to produce the supply line, metering chamber and nozzle structure and passive check valves arranged between the supply line and nozzle chamber and the nozzle structure and metering chamber.

If passive check valves are to be produced, a further fourth layer is provided on the first layer, since the first layer must be selectively etched to expose the valve flap structures of the passive check valves. To make this possible, the passive check valves are arranged laterally, ie in the plane of the layer, in the feed line, dosing chamber and nozzle structure be formed, mobile. A fluid filter element can be produced in the feed line at the same time as the structures mentioned. The first mask step serves to generate the respective structures in the second layer, while the second mask step serves to produce depressions in the third layer opposite the movable valve flap structures. No additional mask is required to etch the first layer to selectively etch the valve flaps.

Further developments of the present invention are set out in the dependent claims.

The present invention and preferred exemplary embodiments thereof are explained in more detail below with reference to the accompanying drawings. Show it:

La to lc are schematic cross-sectional representations to illustrate the functional principle of a metering module working on the basis of a volumetric displacement;

2a to 2c corresponding representations of a dosing module in the presence of an air bubble;

3 shows a diagram of a pressure applied to the discharge opening of such a metering module;

Fig. 4 is a schematic cross-sectional view of an embodiment of an inventive

Freistrahldosiermoduls; 5 shows a schematic plan view of a substrate in which structural elements of an exemplary embodiment of a free jet metering module according to the invention are formed;

6 shows a schematic top view of a substrate in which structural elements of an alternative exemplary embodiment of a free-jet metering element according to the invention are formed;

7a to 7f are schematic cross-sectional representations to illustrate an exemplary embodiment of the method according to the invention.

In Fig. 1 a free jet metering module is shown, which works on the basis of a volumetric displacement. The free jet metering module comprises a reservoir 10, a feed line 12, a metering chamber 14, on which an actuator membrane 16 adjoins on one side, and a nozzle 18 with an ejection opening 20. As shown in FIG. 1 a, the free jet metering module is with a liquid to be metered 22 filled. The free jet metering module can be designed such that the feed line, metering chamber and nozzle are filled by capillary forces. Furthermore, filling can be supported by pressurizing the medium located in the reservoir 10, this pressurization, however, must be so small that no liquid can escape from the discharge opening 20, but a liquid meniscus 24 is retained there.

In such a metering module, the volume of the metering chamber is as a result of a movement of the actuator membrane 16 indicated by dotted lines in Fig. la, changeable.

1b shows a state of the metering module during an ejection process in which the actuator membrane is actuated by an actuating device (not shown), for example a piezo actuator, such that the volume of the metering chamber 14 is reduced, as indicated by an arrow 26. This creates a fluid flow 28 to the nozzle 18, the actuation of the actuator membrane 16 being such that the pressure thereby caused at the discharge opening 20 is sufficient to generate a free jet 30. Furthermore, in the illustrated embodiment, actuation of the actuator membrane 16 also causes a fluid return flow 32, which can be reduced or prevented by suitable measures, for example a higher flow resistance of the feed line 12 compared to the nozzle 18 or the provision of valve elements.

1c shows a refilling process of the dosing chamber after ejection, as shown in FIG. 1b. For this purpose, the actuator membrane 16 is actuated in a direction 34 opposite to the direction of movement shown in FIG. 1b, so that a media flow 36 takes place into the metering chamber 14. A liquid meniscus 24 regulates itself again at the discharge opening 20 of the nozzle 18. The capillary pressure in the nozzle 18 prevents air from being sucked into the nozzle chamber 14 during the refilling process.

It is problematic that known free jet metering modules which operate according to the above principle are not bubble-tolerant. In Figure 2a, this is with reference to the figures above La-lc described free jet metering module, wherein an air bubble 40 is present in the metering chamber. Such air bubbles can get into the dosing chambers, for example, through transport, through diffusion through plastic hose connectors or through the outgassing of supersaturated liquids, for example when there are changes in temperature.

As shown in FIG. 2b, this air bubble is compressed during a metering process, as indicated by arrow 26, as indicated in FIG. 2b by the compressed bubble volume 40a compared to the original bubble volume 40b. As a result of this compression of the air bubble 40, the pressure at the discharge end 20 of the nozzle 18 drops below the free jet limit. Thus, there is no free jet during the ejection process 26, but instead the nozzle is flooded with the medium to be metered, as indicated by the medium 42 in FIG. 2b.

In the subsequent refilling process, which is indicated by the arrow 34 in FIG. 2c, the air bubble 40 remains in the metering chamber 14 and essentially assumes its original volume.

The insufficient bladder tolerance described above is a decisive obstacle in the practical use of microtechnically structured free jet metering modules. The reason for the lack of bladder tolerance is explained in more detail below. To form a free jet, an overpressure must be built up directly on the nozzle, which has a precisely defined geometry, ie a precisely defined discharge opening. The potential energy dW _pot built up by the overpressure supplies the energy dW _whether for the free surface of the free jet and the kinetic Energy dW _{kin of} the beam, which usually still has to be delivered in a targeted manner. The following applies:

pot = dW _ob + dW _kin .

It follows :

p _d A _D = σU _D + mv ² ,

where p _{d is} the pressure prevailing at the discharge opening of the nozzle, A _{d is} the discharge opening area, σ is the surface tension of the medium, U _{D is} the necessary change in area of the surface of the medium to be discharged, m is the mass of the free jet ejected and v is the velocity is the same.

The pressure that is currently required to overcome the surface energy is:

P _re i =

= σU _D / A _D.

A typical value for the free jet limit results for σ = 0.075 N / m and a round nozzle with a diameter of 90 μm: Pfrei = 33 hPa.

The pressure p _fre i _. which is just sufficient for a given nozzle area to generate the surface energy is referred to below as the "free jet limit". If there is now a gas bubble in the metering chamber, this acts, as explained above, as a damping element for those caused by the actuator element in the metering chamber generated overpressures. This reduces the pressure at the nozzle and drops below the free jet limit. The free jet dosing module according to the invention now enables, during a discharge operation at the ejection port almost _re throughout the ejection cycle above the free jet boundary Pf even in the worst case (worst case condition), the pressure p _d at the nozzle, that is the same - to maintain. It is assumed that the actuator that builds up the required pressures is dimensioned such that it can deliver these required pressures, as is the case for conventional microactuators. Ideally, therefore, a rectangular pressure profile is sought, as is designated by the reference symbol 50 in FIG. 3. A practically feasible pressure curve 52 to be aimed for is also shown in FIG. 3.

As can be seen in FIG. 3, both pressure _{profiles lie} above the free jet _limit P _fre i essentially during the entire ejection process. As can be seen, it is advantageous to build up the pressure quickly, typically on the order of 1 ms. Microactuators, in particular those based on piezoelectric or electrostatic, are particularly suitable for this. However, a fundamental problem with the use of microactuator drive principles is that the stroke of the same is very small. With an electrostatic diaphragm drive, it is of the order of 5 μm, while piezoelectric diaphragm drives achieve strokes of 30 μm or more, depending on the diaphragm design. Piezo stack actuators achieve somewhat larger strokes, but are difficult to manufacture.

As a result of the drive membrane driven by micro-actuator drives, only a small stroke volume of a few 10 nanoliters is achieved. Therefore, the compression on ratio ε, which is defined by the ratio between the metering volume ΔV, ie displacement volume of the drive diaphragm, and the dead volume V ₀ , is small in the case of free jet metering modules. The dead volume V ₀ is composed of the metering chamber volume V _k and the nozzle chamber volume V _d . The compression ratio ε is defined as:

ε = ΔV / Vo

The free jet metering module can then generate a free jet if the pressure p _d generated at the discharge opening of the nozzle _is greater than the free jet limit Pf _re i. The condition for a free jet is therefore:

I Pd l> I Pfrei l •

A worst-case analysis for a bubble-tolerant dosing module is now carried out. The worst case would occur if the entire metering chamber was filled with the volume V _k including the volume between the metering chamber and the discharge opening of the nozzle (nozzle chamber volume V _d ) with air, which is a compressible gaseous medium, with a volume V _gas , ie:

Vgas V _n = Vw + V _ri

In this worst-case scenario, the damping effect described above is maximum. During the ejection process, the actuator membrane compresses this air volume. The maximum pressure at the nozzle is then determined by the pressure in the air bubble. The pressure at the nozzle p _{d is} calculated from the equation of the air bubble:

Where γ _{A is} the adiabatic coefficient of the gas, P _{0 is} the atmospheric pressure, which can be assumed to be p ₀ = 1013 hPa, and ΔV is the change in volume due to the compression of the gas bubble. Together with the above-mentioned condition for the free jet, the minimum compression ratio of bubble-tolerant free jet modules is as follows:

YA ε> Po - 1

PoHP ripe

If the free jet limit p _{3 is} small compared to the atmospheric pressure po, which is fulfilled, for example, when p ₃ = 33 hPa compared to p ₀ = 1013 hPa, the above equation can be simplified to:

ε> 1 P free

In the case of rapid changes in state, the ratios are adiabatic, γ _A = 1.4 for air, in the case of slow changes in state, isothermal, γ _A = 1. With consistent use of the worst-case assumption, according to the invention, the criterion γ _A = is used to determine the minimum necessary compression ratio 1 used. As a rule of thumb for the necessary compression ratio of free jet metering modules, the compression ratio of bubble-tolerant free jet dispensers must be greater than the ratio of the free jet _limit P _fre i to atmospheric pressure, ie _ε > ----- £ --__

po

With the above volumes:

This results in the dimensioning of the free jet dispenser according to the invention in such a way that the ratio of the displaced volume of the actuating device and the dead volume, i.e. the sum of the dead volume of the metering chamber and the nozzle chamber is greater than the ratio of the pressure required for the formation of a free jet to the atmospheric pressure. This ensures that the maximum pressure occurring in the air bubble during the ejection process is greater than the free jet limit. The consequent application of the worst case assumption results in an excess potential energy, which gives the beam a kinetic energy and thus a defined direction. Furthermore, the energy available for the kinetic energy can be increased by a corresponding further increase in the compression ratio.

As has been explained above, the drive is advantageously designed in such a way that the volume can be compressed very quickly, ie microactuators, in particular those based on piezoelectric or electrostatic, are advantageously used. Such actuators must also be suitable for abruptly stopping the volume change, so that the pressure flank drops steeply and the jet breaks off in a defined manner. Such a rapid pressure drop can be achieved by the drive being designed to actively pull back the actuator membrane hen. Alternatively, the metering chamber, actuator membrane and actuating device can be designed in such a way that the actuator membrane is braked abruptly from movement in the ejection phase by hitting a stop. For example, the free jet metering module can be designed such that the actuator membrane strikes the opposite chamber wall or protrusions formed on the same, thereby stopping its movement. If the force with which the membrane is acted upon were sufficient without a stop to deflect it further, the abrupt braking would result in an abrupt drop in pressure and thus a defined break at the discharge opening.

In a free jet metering device according to the invention with the compression ratio described, the flow resistance of the feed line can be defined greater than the flow resistance of the nozzle chamber. This will force most of the volume out of the nozzle and not back into the reservoir. However, the ratio depends on the rheological properties of the liquid. In a free jet metering module according to the invention, therefore, a valve element is preferably arranged between a supply line and the metering chamber, which valve element can be, for example, a diffuser nozzle element (diffuser nozzle), a passive check valve or an active valve. Diffuser nozzle element is understood to mean a tapering element which has a preferred direction of flow.

The provision of a valve element between the feed line and the metering chamber ensures that the entire volume to be displaced is expelled by the valve action. Another disadvantage of the feed line being that the flow resistance is too great is that the refilling takes place very slowly, which drastically reduces repetition frequencies. In addition, the negative pressure during refilling must not exceed the capillary pressure of the meniscus at the ejection end of the nozzle even during normal operation, ie a complete filling of the pump chamber with a medium to be dosed. Preferred exemplary embodiments of the present invention therefore also include a valve element between the discharge opening of the nozzle and the metering chamber, which in turn can be, for example, a diffuser nozzle element, a passive non-return element or an active valve.

Such a valve between the metering chamber and nozzle ejection opening has the advantage in normal operation, ie when the metering chamber is completely filled with liquid, that it is ensured that when the metering chamber is refilled, a significantly higher negative pressure may occur than without this valve. As a result, the refilling process is not limited to a maximum repetition frequency of approx. 10 Hz. The suction time is rather independent of the capillary pressure. In the event of a malfunction, ie in the presence of a gas bubble in the metering chamber, the valve ensures that the volume displaced by the actuator element only flows in from the reservoir line, whether air or liquid. If this valve were not provided, the dosing chamber would also be filled by capillary forces, but only if the dosing chamber had wetting properties in relation to the medium to be dosed. This is the filling process caused by capillary forces slowly and depending on the rheological properties of the medium to be filled.

In the most general case, a free-jet metering device according to the invention has a structure corresponding to FIGS. 1 and 2 (supply line and reservoir optional), the metering chamber 14 and the nozzle 18 being designed in such a way that the defined ratio of their volumes to the displacement volume is fulfilled.

A schematic cross-sectional view of an embodiment of a free-jet metering module according to the invention provided with check valves is shown in FIG. 4. The free jet metering module is formed by a micromembrane pump 60 and a nozzle chip 62 connected to it. The structure of the micromembrane pump 60 can essentially correspond to the structure of the micromembrane pump described in DE 19719862 A1, but the condition stated with regard to the compression ratio must be observed for use in the free-jet metering module according to the invention. In addition, the compression ratio must be at least as large in order to additionally generate the pressure that is necessary to open the valve flap of the passive check valve between the pump and the nozzle.

As shown in FIG. 4, the micro diaphragm pump 60 comprises an actuating device 64, preferably in the form of a piezo actuator. The actuator 64 is attached to a membrane 68 formed in a membrane chip 66. The micromembrane pump 60 further comprises a first valve chip 70 and a second valve chip 72. In the valve chips, respective structures are defined, which are at the inlet and provide respective passive check valves 74 and 76 at the outlet of the micro diaphragm pump. The construction and manufacture of such passive check valves can be conventional and therefore requires no further discussion here.

A pump chamber 78 of the micromembrane pump, which represents the metering chamber according to the invention, is defined by the valve chips 70 and 72 and the membrane chip 66. The nozzle chip 62 is in this way on the micromembrane pump, i.e. attached to the second valve chip 72 thereof, that a nozzle 80 formed therein is connected via the valve element provided to the outlet of the micromembrane pump, which is provided with the check valve 76. Furthermore, a passage opening 82 is provided in the nozzle chip 62, via which the inlet of the micromembrane pump 60, which is provided with the check valve 74, is connected to a feed channel 84, which in turn is fluidly connected to a reservoir 86.

In the exemplary embodiment shown in FIG. 4, the free jet metering module according to the invention is thus formed by a micromembrane pump with a separate nozzle chip, this free jet metering module having a reservoir 86 with a corresponding feed line 84. The structure in which the reservoir and feed line are formed can be produced separately from the free jet metering module, which consists of micropump 60 and metering chip 62, and can then be connected to the same.

In the embodiment shown in FIG. 4, which has a valve element at the outlet end of the micropump, it should be noted that the free jet limit is determined by the pressure. which is necessary to open the valve 76 provided at the outlet end. This pressure required to open the valve flap is made up of the restoring forces of the valve flap and the forces which have to be applied in order to overcome forces which occur due to a wetting state of the valve opening and which counteract an opening force of the valve flap. Here the compression ratio is to be chosen larger than the ratio of the sum of the free jet pressure and the pressure required to open the passive check valve to the atmospheric pressure. In order then to provide the expelled free jet 90 with sufficient kinetic energy, the compression ratio can again be chosen to be correspondingly higher.

A preferred method for producing a free-jet metering module is described in more detail below with reference to FIGS. 5 to 7. In particular, such a method can advantageously be used to generate a free jet metering module with the compression ratios described above.

As shown in FIG. 7 a, a three-layer structure is used as the starting structure, which has a silicon wafer 92, an oxide layer 94 and a silicon layer 96. A so-called SOI wafer (SOI = Silicon on Insulator) or BESOI wafer (BESOI = Bonded Etched Back Silicon On Insulator) can advantageously be used as such a three-layer structure. Alternatively, other layer materials can be used, which enable processing through the subsequent steps. Fluid channels, valve flaps, a pump chamber and a nozzle channel are produced in the silicon layer 96 of thickness D in a subsequent anisotropic dry etching, preferably in an etching step.

A schematic view of an exemplary embodiment of the silicon layer 96 after the anisotropic dry etching thereof is shown in FIG. 5. As can be seen there, a dosing chamber 100, a Dosierka mereinlaß 102 and a dosing chamber outlet 104 are generated by the anisotropic dry etching. As can be seen in Fig. 5, both the inlet 102 and the outlet 104 are provided with a sealing lip in the illustrated embodiment. Furthermore, an inlet valve flap 106 and an outlet valve flap 108 are produced in the silicon layer 96. The valve flap 106 forms an inlet valve together with the inlet 102, while the valve flap 108 forms an outlet valve together with the outlet 104. A nozzle chamber 110 and a feed line 112 are also produced in the silicon layer 96. The feed line comprises a widened area 114, in which projections 116 remain, so that this area acts as a fluid filter. In addition to the structures mentioned, predetermined breaking points 120, 122 are also provided in the silicon layer 96 during the anisotropic dry etching, along which breakage can later take place, on the one hand to expose the feed line 112 and on the other hand a discharge opening 124 of the nozzle, i.e. to realize the nozzle chamber 110.

An alternative structuring of the silicon layer 96 during the anisotropic dry etching (FIG. 7b) is shown in FIG. 6. Structures in the exemplary embodiment shown there, which essentially correspond to those of FIG. 5, are identified by the same reference numerals. In the exemplary embodiment shown in FIG. 6, no fluid filter is provided in the feed line 112. In the example shown in FIG. 6, projections 126 are provided in the wall of the nozzle chamber 110 opposite the outlet valve flap 108, which serve to prevent the valve flap 108 from adhering to this wall in the open state.

After the structures in the silicon layer 96 have been produced, the valve flaps are selectively etched free, preferably HF etching, so that the oxide layer in the region below the valve flaps 106 and 108 (FIG. 5) is removed so that the latter is in the plane of the silicon layer 96 are laterally movable. The width of the valve flaps 106 and 108 is designed to enable the etching of the oxide layer 94 by HF etching. Typical suitable widths of the valve flaps can be in a range from 5 to 30 μm.

The resulting structure is shown in Fig. 7c. 7c, a silicon layer 130 is shown, in which recesses or depressions 132 are formed opposite the valve flaps 106 and 108 by anisotropic dry etching, in order to prevent the valve flaps from being firmly bonded when the silicon layer 130 is subsequently connected to the silicon layer 96, so that the valve flaps remain movable. The recesses can have a depth of 1 to 3 μm, for example.

At this point it should be noted that the respective fluid passages 102 and 104 through the valve flaps 106 and 108 are not completely closed due to the undercut of the valve flaps and the creation of the recesses 132. can be sen. Due to the depth of the non-closable sections of the order of magnitude of 1 to 3 μm, however, they have such a high flow resistance that flow through them is negligible, so that the respective fluid passages can be regarded as essentially closable by the valve flaps.

The layers 96 and 130 are preferably connected by conventional wafer bonding using OH groups. For this purpose, a thin oxide layer is produced to support at least one of the layers, but this is not a joining layer in the classic sense, so that wafer bonding can be described as having no joining layer.

The resulting structure after this step of connecting is shown in FIG. 7d, wherein it can be seen that the metering chamber 100 is formed by the step of connecting. At this point it should be stated that Figures 7a to 7f are purely schematic, so that the valve structures produced are only shown as undercut sections 134 and 136 in them.

After the two wafers have been joined without a layer, a passivation layer 138 is applied to the upper side of the wafer 92, whereupon the silicon layer 130 is thinned from the exposed rear side thereof in order to produce the silicon actuator membrane 140 for the free-jet metering module, as shown in FIG. 7e ,

The layer 130 can, for example, be subjected to a full-area KOH thinning or a whole-area thinning by grinding. Alternatively, a structured fertilizer only the areas of the layer 130 that are to serve as an actuator membrane. As an alternative to the process-related treatment of the layer 130 to produce the membrane after the application thereof, the layer 130 can already be applied with a thickness which, at least in the actuator membrane regions, corresponds to the desired membrane thickness.

A drive device is subsequently applied to the silicon actuator membrane 140. In the exemplary embodiment shown, a metallization layer 142 is first applied to the exposed surface of the layer 130 and subsequently a piezoceramic 144 is applied, preferably glued, to the metallization layer 142.

As an alternative to gluing the piezoceramic, a piezostack (piezostack) can be brought into contact with the actuator membrane in such a way that the actuator membrane can be actuated by the same. The use of a piezo stack enables greater forces and larger strokes, but is more complex than a glued-on piezo ceramic. The use of a piezo stack is thus particularly suitable for a modular construction in which the actuating device is not permanently connected to the rest of the free jet metering module and is therefore reusable.

Finally or before attaching the actuating device, the discharge opening of the nozzle chamber 110 and an inlet opening of the feed line 112 are opened by breaking along the predetermined breaking points 120 and 122. Breaking is advantageous in that it is done dry. Alternatively, the above openings could be sawn the layer structure are generated, with the risk that the openings are contaminated by saw water and saw dust used. Another method for separating or creating the openings is to carry out laser cutting, which is also a dry method and also provides defined nozzle areas. Furthermore, it is not necessary to create the openings laterally. Rather, the inlet inlet opening and / or the discharge opening could be formed by layers 130 and 142 downwards and / or by layers 92 and 138 upwards.

The method described above is particularly suitable for producing a free jet metering module, the compression ratio of which fulfills the condition described above. This is particularly advantageously possible if anisotropic dry etching is used instead of a KOH structuring for the etching steps mentioned. The anisotropic dry etching enables a small dead volume in the dosing chamber using only a single process step. Any channel and chamber geometries can also be implemented. In addition, only two masks are required in order to generate the free jet metering module when using an anisotropic dry etching by the described method. As was described in particular with reference to FIG. 5, the anisotropic dry etching further enables the integration of a fluid filter in the feed line. In addition, this enables a small dead volume in the valve area.

In addition to the connectionless connection of the two wafers described above, they can also be connected to one another using a connection layer. In one In such a case, the connecting layer has recesses in the region of the valve flap structures, so that these valve flaps in turn remain movable in the plane of the layer in which they are formed.

The present invention thus provides a method for producing a fluid module which has a layer in which a fluid chamber with an inlet and / or outlet is structured, and in which one or more valve flaps are also provided for the inlet and / or outlet which are movable in the plane of the layer to close the inlet and / or outlet. The method according to the invention thus deviates from known methods in which valve flap structures were each movable perpendicular to the plane of the layer in which they are formed. The production and arrangement of valve flaps according to the invention advantageously enables the production of free jet metering modules which have a high compression ratio with very few mask processes. In addition to the methods described, other technologies, for example injection molding technology or precision machining processes, can also be used to produce the free jet metering module according to the invention.

As explained above, with the free jet metering module according to the invention, metering takes place on the basis of fast, time-dependent processes in the metering chamber and the nozzle chamber. In such processes, the real pressure available at the discharge opening of the nozzle depends on the friction and the inertia of the medium to be dosed in the nozzle chamber and dosing chamber. More specifically, there is a pressure drop between the point at which the actuator membrane generates the pressure and the discharge opening, where the pressure available at the discharge opening is lower by this pressure drop than the pressure generated by the actuator membrane. This pressure drop must be taken into account when setting the compression ratio. The free jet metering module according to the invention is therefore advantageously designed so that this pressure drop is as low as possible and is therefore negligible.

The friction mentioned above depends on the third power of the dosing chamber height. In order to minimize friction losses, it would therefore be advantageous to provide the metering chamber with the greatest possible height. However, in order to be able to pay for the necessary compression ratio, it must be ensured that the actuator membrane can displace a large part of the metering chamber volume or the entire metering chamber volume. For this purpose, the actuator consisting of the membrane and the actuating device must be designed accordingly. Furthermore, the shape of the metering chamber can be such that it is adapted to the shape of the actuator membrane in the deflected state.

In preferred exemplary embodiments of the present invention, the metering chamber height of the free jet metering module described with reference to FIGS. 5 to 7 is therefore set, for example, to be greater than 10 μm, preferably greater than 20 μm or 30 μm. Depending on the height of the metering chamber, the drive must be selected so that the necessary compression ratio can still be generated, so that the metering chamber height cannot be as large as desired. For example, it may be preferred to choose the height, ie the distance between the actuator membrane and the opposite chamber wall in the unactuated state, of the metering chamber below 50 μm. In the method described with reference to FIGS. 5 to 7, the thicknesses of the layers 96 and 94 can thus preferably be chosen such that the metering chamber has a height corresponding to the above statements. Depending on the thickness of the oxide layer 94, a silicon layer 96 with a thickness of more than 10 μm and more preferably a silicon layer 96 with a thickness of more than 10 μm and less than 50 μm can therefore be used in the described method.

A dosing chamber height as described above, however, leads to an increased ejected dosing volume. In an alternative exemplary embodiment, the pressure drop described above is kept low by arranging the nozzle with its ejection opening essentially in the center opposite the actuator membrane. For example, in the construction shown in FIG. 4, the nozzle could be arranged centrally below the actuator membrane. However, such an arrangement is also possible without a valve between the metering chamber and nozzle, i.e. Ejection opening of the same possible. With such a construction, the friction losses and inertia losses described above are essentially minimized, and the discharge of small metering volumes is possible.

After, as the above explanation shows, the free jet metering module according to the invention is designed to remain operable even when it is completely filled with a compressible gaseous medium, the free jet metering module according to the invention is also suitable for conveying or metering gaseous media. A free jet metering module with a single metering chamber and a single nozzle chamber was described above. A free jet metering module according to the invention can moreover have a plurality of metering chambers and associated nozzles which are arranged in a one-dimensional or two-dimensional array, so that the nozzles have a predetermined positional relationship to one another. Such a module with an array of individual ejection devices can easily be produced by producing a plurality of ejection devices at the wafer level at the same time. For example, the method described with reference to FIGS. 5 to 7 can be used to produce a plurality of ejection devices arranged in a row, the inlet openings and ejection openings of which are then opened together. Alternatively, two-dimensional arrays can be produced, in which case inlet openings and discharge openings are preferably led out upwards and / or downwards.

Claims

claims

1. Free jet metering module with the following features:

a dosing chamber (78; 100) with a dosing chamber volume;

an actuating device (64, 68; 130, 142, 144) adjoining the metering chamber (78; 100), which reduces the metering chamber volume by a displacement volume when actuated;

an ejection opening (80; 124) fluidly connected to the dosing chamber (78; 100), a nozzle volume being defined by a fluid region existing between the dosing chamber and the ejection opening;

the ratio of the displacement volume and the sum of the metering chamber volume and the nozzle volume being greater than the ratio of a free jet pressure to the atmospheric pressure in order to generate a free jet at the discharge opening, even if a compressible gaseous medium substantially filling the metering chamber volume and the nozzle volume were present, the free jet pressure being the pressure required in the metering chamber which is just sufficient for a given discharge opening area to generate the surface energy in order to cause a free jet at the discharge opening.

2. Free jet metering module according to claim 1, further comprising a feed line (84; 112) for supplying a metered renden medium in the metering chamber (78; 100).

3. Free jet metering module according to claim 2, further comprising a valve element (74; 106) to during a

Ejection phase to reduce or prevent fluid flow through the supply line (84; 112).

4. free jet metering module according to one of claims 1 to 3, further comprising a valve element (76; 108) between

Ejection opening (124) and dosing chamber (78; 100) in order to reduce or prevent a fluid flow between the ejection opening and dosing chamber during a refilling phase.

Free jet metering module according to claim 3 or 4, wherein the respective valve element (74, 76; 106, 108) is a passive check valve, an active valve or a diffuser nozzle element.

6. Free jet metering module according to claim 4, wherein the valve element (76; 108) between the discharge opening (124) and the metering chamber (100) is a passive check valve, and in which the ratio of displacement volume and the sum of metering chamber volume and nozzle volume is greater than the ratio of the sum of the free jet pressure and the pressure required to open the passive check valve to the atmospheric pressure.

The free jet metering module of claim 2, further comprising a fluid reservoir (86) over the feed line (84) is fluidly connected to the metering chamber (78).

8. Free jet metering module according to one of claims 3 to 6, in which the metering chamber (78; 100) is at least partially defined by a recess in a substrate (96), and in which the valve element or elements movable in the plane of the substrate into which Has structured valve flaps (106, 108).

9. free jet metering module according to one of claims 1 to

8, in which the metering chamber and the actuating device are formed by a micromembrane pump (60) which is connected to a nozzle chip (62) in which a nozzle (80) is formed with an ejection opening in such a way that the ejection opening is connected to an outlet of the Micro diaphragm pump is fluidly connectable.

10. Free jet metering module according to one of claims 1 to

9, in which the discharge opening is arranged essentially opposite the actuator membrane.

11. Free jet metering modular array with a plurality of free jet metering modules according to one of claims 1 to 10, the discharge openings of which are arranged in a one-dimensional or two-dimensional array.

12. A method for producing a free jet metering module, with the following steps:

Providing a layer composite of a first layer (94) and a second layer (96); Etching at least one dosing chamber structure (100) and a nozzle structure (110) fluidly connected to the same, reaching as far as the first layer (94) in the second layer (96);

Connecting a third layer (130) to the second layer (96) to produce a metering chamber and a nozzle chamber,

wherein the third layer has a thickness to define an actuator membrane (140) adjacent to the dosing chamber, or wherein the third layer (130) is processed after application thereof to produce an actuator membrane (140) adjacent to the dosing chamber.

13. The method of claim 12, wherein the step of etching comprises a step of dry anisotropic etching of the second layer.

14. The method as claimed in claim 12 or 13, in which, in the step of etching the second layer (96), a supply structure (112) for the metering chamber is also produced in the second layer.

15. The method as claimed in claim 14, in which, in the step of etching the second layer (96), a filter structure (114, 116) is also produced in the feed structure (112).

16. The method of claim 14 or 15, further comprising a step of opening an exhaust port for the du- lower chamber and / or an inlet opening for the supply line by breaking the layer structure at at least one predetermined breaking point (122), by sawing the layer structure or by laser cutting the layer structure.

17. The method of claim 14 or 15, further comprising a step of opening a discharge opening for the nozzle chamber and / or an inlet opening for the feed line by creating openings through the first layer and / or the third layer.

18. The method according to any one of claims 12 to 17, wherein the connection of the second and third layers (96, 130) is carried out by a wafer bonding.

19. The method according to any one of claims 12 to 18, wherein the layer composite provided further comprises a fourth layer (92) which is connected to the first layer (94).

20. The method according to claim 19, wherein the layer composite of first, second and fourth layer (92, 94, 96) is an SOI wafer or a BESOI wafer.

21. The method according to any one of claims 12 to 20, wherein in the step of etching the second layer (96) furthermore at least one valve flap structure (106, 108) and a fluid passage (102, 104) essentially closable by the same in the second Layer (96) is generated, and further comprising the following steps: Etching the first layer (94) in the region of the valve flap structure (106, 108) to produce a valve flap structure movable in the plane of the second layer; and

Etching recesses (132) in the third layer (130) which, after the connection of the second and the third layer (96, 130), lie opposite the valve flap structure (106, 108), so that after the connection of the second and third layer ( 96, 130) remain mobile.

22. The method according to any one of claims 12 to 21, wherein in the step of etching the second layer (96) furthermore at least one valve flap structure (106, 108) and a fluid passage (102, 104) closable by the same in the second layer ( 96), which further comprises a step of etching the first layer (94) in the region of the valve flap structure in order to produce a valve flap structure which is movable in the plane of the second layer, wherein in the step of connecting the third layer to the second layer, a connecting layer is used, which has a recess in the area of the valve flap structure, so that the valve flap structure remains movable after the connection.

23. The method of claim 21 or 22 with reference to claim 13 or 14, wherein in the step of etching the second layer (96) a lead structure (112) is further formed in the second layer, wherein a closable fluid passage (102) between Do - sierkammerstruktur (100) and supply structure (112) is arranged.

24. The method according to one of the steps 21 to 23, in which a closable fluid passage (104) with an associated valve flap structure (108) is generated between the metering chamber structure (100) and the nozzle structure (110).

25. The method according to any one of claims 12 to 24, further comprising a step of attaching an actuating device (144) to the actuator membrane (140) in order to reduce a volume of the dosing chamber (100) by a displacement volume when actuated, wherein the metering chamber, the nozzle chamber, the actuator membrane and the actuating device are dimensioned such that the ratio of the displacement volume and the sum of a volume of the metering chamber and a volume of the nozzle chamber is greater than the ratio of a free jet pressure to the atmospheric pressure in order to generate a free jet at the discharge opening , even if there was a compressible gaseous medium essentially filling the dosing chamber volume and the nozzle chamber volume, whereby the free jet pressure is the pressure required in the dosing chamber that is just sufficient for a given discharge opening area of a discharge opening of the nozzle chamber to reduce the surface energy e to generate a free jet at the discharge opening.

26. Method for producing a free jet metering module array with a plurality of free jet metering module len, the ejection openings of which are arranged in a one-dimensional or two-dimensional array, the respective free jet modules being produced using a method according to one of Claims 12 to 25.