EP1458977B1 - Peristaltic micropump - Google Patents

Peristaltic micropump Download PDF

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Publication number
EP1458977B1
EP1458977B1 EP03792417A EP03792417A EP1458977B1 EP 1458977 B1 EP1458977 B1 EP 1458977B1 EP 03792417 A EP03792417 A EP 03792417A EP 03792417 A EP03792417 A EP 03792417A EP 1458977 B1 EP1458977 B1 EP 1458977B1
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Prior art keywords
membrane
valve
membrane region
pump body
pumping chamber
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German (de)
French (fr)
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EP1458977B2 (en
EP1458977A1 (en
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Yücel CONGAR
Julia Nissen
Martin Richter
Martin Wackerle
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Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
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Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
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Priority to DE2002138600 priority Critical patent/DE10238600A1/en
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Priority to PCT/EP2003/009352 priority patent/WO2004018875A1/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00Machines, pumps, or pumping installations having flexible working members
    • F04B43/02Machines, pumps, or pumping installations having flexible working members having plate-like flexible members, e.g. diaphragms
    • F04B43/04Pumps having electric drive
    • F04B43/043Micropumps
    • F04B43/046Micropumps with piezo-electric drive
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00Machines, pumps, or pumping installations having flexible working members
    • F04B43/02Machines, pumps, or pumping installations having flexible working members having plate-like flexible members, e.g. diaphragms
    • F04B43/04Pumps having electric drive
    • F04B43/043Micropumps

Description

The present invention relates to a micropump and in particular a micropump following a peristaltic Pump principle works.

Micropumps that operate on a peristaltic pumping principle are known from the prior art. So busy the article "Design and simulation of an implantable medical drug delivery system using microelectromechanical systems technology ", by Li Cao et al., Sensors and Actuators, A94 (2001), pages 117 to 125, with a peristaltic Micropump, one inlet, three pumping chambers, three Silicon membranes, three normally-closed active valves, three piezo stack actuators made of PZT, microchannels between the pumping chambers and an outlet. The three pumping chambers are of equal size and are in one Etched silicon wafer.

From WO 87/07218 is also a peristaltic micropump known, the three membrane areas in a continuous Substrate surface has. In a carrier layer, the the substrate and an associated support layer carries is a pumping channel formed with a fluid reservoir in Connection stands. In the pumping channel is in the range of Inlet valves and an outlet valve each have a transverse rib formed on the associated membrane portion in the unactuated state rests to in the unactuated state to close the inlet valve and the outlet valve. Between the intake valve and the exhaust valve assigned separately operable membrane areas is the third membrane area, which can also be operated separately is arranged. By actuating the third membrane area the chamber volume between the two valve areas elevated. Thus, by a corresponding time controlled activation of the three membrane areas one peristaltic pump action between inlet valve and outlet valve be achieved. According to WO 87/07218 the actuator element of a triple composite of metal membrane, continuous ceramic layer and segmented electrode arrangement. The ceramic layer must be segmented polarized, which is technically difficult. One Such segmented piezo-bending element is thus expensive and allows only small strokes, so that a Such pump not bladder tolerant and self-priming can work.

From DE 19719862 A1 is one, not on the peristaltic Principle working, known micromembrane pump, at the one by a pumping chamber adjacent pumping membrane a piezoelectric actuator can be actuated. A fluid inlet and a Fluid outlet of the pumping chamber are each with passive check valves Mistake. According to this document, the compression ratio the micropump, d. H. The relationship from the stroke volume of the pumping membrane to the total pumping chamber volume depending on the maximum of the valve geometry and the Valve wetting dependent pressure value necessary to open the valves, set to a bubble-tolerant, self-priming operation of the local micromembrane pump to enable.

In addition to the above-mentioned piezoelectric actuators, it would also be possible Micropumps using electrostatic actuators to realize, however, electrostatic actuators allow only very small strokes. Alternatively, would be the Realization of pneumatic drives possible, but what a high effort in terms of external pneumatics as well the necessary switching valves necessary. Pneumatic drives thus make complex, expensive and space-consuming procedures to increase membrane deflection to implement.

The object of the present invention is to provide a to create peristaltic micromembrane pump that easy can be built and the one bubble-tolerant, self-priming operation allows.

According to the invention, this object is achieved by a peristaltic Micropump solved according to claim 1.

The present invention provides a peristaltic micropump having the following features:

  • a first diaphragm region having a first piezoactuator for actuating the first diaphragm region;
  • a second diaphragm region having a second piezoactuator for actuating the second diaphragm region;
  • a third diaphragm region having a third piezoelectric actuator for actuating the third diaphragm region; and
  • a pump body which forms, together with the first membrane region, a first valve whose passage opening is open in the unactuated state of the first membrane region and whose passage opening can be closed by actuation of the first membrane region, which together with the second membrane region forms a pumping chamber whose volume is controlled by actuation of the first membrane region the second membrane region can be reduced, and forms, together with the third membrane region, a second valve whose passage opening is open in the unactuated state of the third membrane region and whose passage opening can be closed by actuating the third membrane region,
  • wherein the first and second valves are fluidly connected to the pumping chamber.

    The present invention thus provides a peristaltic Micropump, with the first and the second valve in the unactuated State are open, and at the first and the second valve by moving the membrane to the pump body can be closed while the volume the pumping chamber by moving the second membrane area can also be reduced to the pump body.

    With this structure, the peristaltic invention allows Micropump the realization bubble tolerant, self-priming pumps, even when placed on a diaphragm Piezo elements are used as a piezoelectric actuator. Alternatively, according to the invention as piezo actuators also so-called Piezo Stacks (Piezo Stacks) can be used however disadvantageous to piezo membrane transducers are that they are big and expensive, problems concerning the connection technology between stack and membrane and Problems in adjusting the stack deliver and thus overall associated with a higher cost.

    To ensure that the peristaltic Micropump is bubble-tolerant and self-priming can, it is preferably dimensioned such that the ratio of stroke volume and dead volume is greater than one Ratio of delivery pressure and atmospheric pressure is, where the stroke volume the volume displaceable by the pump membrane is, the dead volume between the inlet port and outlet port the micropump remaining volume when the Pump diaphragm is actuated and one of the valves closed and one is open, the atmospheric pressure is maximum is about 1050 hPa (worst case consideration), and the Delivery pressure in the fluid chamber region of the micropump, d. H. in the pressure chamber, necessary pressure is to one Liquid / gas interface in one place, the one Flow restriction in the microperistaltic pump, i. between the pumping chamber and the passage opening of the first or second valve, including this passage opening, represents moving past.

    Suffice the ratio of stroke volume and dead volume, the may be referred to as the compression ratio, the above Condition, it is ensured that the peristaltic Micropump is bubble-tolerant and self-priming. This applies both when using the peristaltic micropump for conveying liquids when a gas bubble, usually an air bubble, in the fluid area of the pump as well as when using the micropump according to the invention as a gas pump when inadvertently damp condensed from the gas to be pumped and thus a Gas / liquid interface in the fluid region of the pump can occur.

    Compression ratios satisfying the above condition can be realized according to the invention, for example, by making the volume of the pumping chamber larger than that of between the respective valve membrane areas and opposite valve body sections formed valve chambers. In preferred embodiments, this can be realized by the distance between membrane and Surface and pump body surface in the area of the pumping chamber larger than in the area of the valve chambers.

    Another increase in the compression ratio of a Peristaltic micropump according to the invention can be achieved be characterized by the contour of a structured in the pump body Pumping chamber to the bending line of the pumping membrane, d. H. the curved contour of the same in the actuated state, adapted is, so that the pumping diaphragm in the actuated state in essentially displace the entire volume of the pumping chamber can. Furthermore, the contours of in the pump body can also formed valve chambers according to the bending line adapted to the respective opposite membrane sections be, so that in the optimal case in the closed state of actuated membrane area substantially the entire valve chamber volume repressed.

    Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings. Show it:

    Fig. 1
    a schematic cross-sectional view of an embodiment of a peristaltic micropump according to the invention in a fluid system;
    Fig. 2a
    to 2f are schematic representations for explaining a piezo-membrane converter;
    Fig. 3a
    to 3c are schematic cross-sectional views for explaining the terms of stroke volume and dead volume;
    Fig. 4
    a schematic diagram showing the volume / pressure Zugstände during a pumping cycle;
    Fig. 5a
    to 5c are schematic representations for explaining the term delivery pressure;
    Fig. 6a
    to 6c are schematic views of an alternative embodiment of a micropump according to the invention;
    Fig. 7
    an enlarged view of a portion of Fig. 6b;
    Fig. 8
    an enlarged schematic cross-sectional view of a modified portion of Fig. 7;
    9a,
    Figures 9b and 9c are schematic illustrations of possible pumping chamber designs;
    Fig. 10a
    and Fig. 10b are schematic representations of an alternative embodiment of a micropump according to the invention;
    Fig. 11
    13 to 13 are schematic cross-sectional views of enlarged portions of modifications of the example shown in Figs. 10a and 10b;
    Fig. 14
    a schematic cross-sectional view of another alternative embodiment of a micropump according to the invention;
    Fig. 15
    a schematic representation of a multi-micropump according to the invention; and
    Fig. 16
    a schematic representation of an alternative embodiment of a micropump according to the invention.

    A first embodiment of a peristaltic according to the invention Micropump integrated into a fluid system is shown in Fig. 1. The micromembrane pump includes a membrane element 10, the three membrane sections 12, 14th and 16. Each of the membrane sections 12, 14 and 16 is provided with a piezoelectric element 22, 24 and 26 and forms together with the same a piezo-membrane transducer. The Piezo elements 22, 24, 26 can be applied to the respective membrane sections be glued or can by screen printing or other thick film techniques may be formed on the membrane.

    The membrane element is circumferential at outer regions thereof joined to a pump body 30, so that between the same is a fluid-tight connection. In the pump body 30, two fluid passages 32 and 34 are formed, one of which, depending on the pumping direction, a fluid inlet and the other is a fluid outlet. In the in Fig. 1 embodiment, the fluid passages 32, 34 each surrounded by a sealing lip 36.

    Furthermore, in the embodiment shown in Fig. 1 the underside of the membrane element 10 and the top of the Pump body 30 structured to a fluid chamber 40 between to define it.

    In the embodiment shown, both the membrane element 10 and the pump body 30 in a respective Silicon wafer implemented, so that the same example joined together by Silicon Fusion Bonding could be. As can be seen from Fig. 1, the membrane element 10 in the top of the same three recesses and in the bottom of the same a recess on to the three membrane areas 12, 14 and 16 to define.

    By the piezoelectric elements or piezoceramics 22, 24 and 26 the membrane sections 12, 14 and 16 are each in the direction on the pump body 30 to be actuated, so that the Membrane section 12 together with the fluid passage 32 a Inlet valve 62 is that by actuating the membrane portion 12 can be closed. In the same way represent the diaphragm section 16 and the fluid passage 34th together an outlet valve 64, which by pressing the Diaphragm section 16 closed by means of the piezoelectric element 26 can be. Finally, by pressing the piezoelectric element 24, the volume of the valve disposed between the valves Pump chamber area 42 reducible.

    Prior to the operation of the peristaltic shown in FIG Micropump is received, initially short the fluid system environment into which the micropump of FIG. 1 is installed described. The pump is with the Pump body 30 glued to a support block 50, optionally, As shown in Fig. 1, grooves 52 in the support block 50 may be provided to excess adhesive take. For example, the grooves 52 may be in the support block 50 formed fluid channels 54 and 56 surrounding provided be to pick up excess glue and to prevent the same in the fluid channels 54, 56 and the Fluid passages 32, 34 passes. The pump body 30 is glued or joined to the support block such that the fluid passage 32 in fluid communication with the fluid channel 54 and that the fluid passage in fluid communication with the fluid channel 56 is. Between the fluid channels 54 and 56 may in the Carrier block 50 another channel 58 as a cross leak protection be provided. At the outer ends of the fluid channels 54, 56 fittings 60 are provided, for example for attaching hose lines to that shown in Fig. 1 Serve fluid system. Further, in Fig. 1 schematically shown a housing 61, for example, below Use of an adhesive bond to the carrier block 50 is added to provide protection for the micropump and complete the piezo elements moisture-proof.

    For the description of a peristaltic pump cycle the in Fig. 1 pump is initially of an initial state assumed that the inlet valve 62 is closed is the second diaphragm section 14 corresponding Pumping diaphragm is in the de-energized state and the exhaust valve 64 is open. Starting from this state is through Actuate the piezoelectric element 24, the pumping membrane 14 down moves, which corresponds to the pressure stroke, causing the stroke volume through the open exhaust valve into the outlet, d. H. the fluid channel 56 is conveyed. Compressing the Pumping chamber 42 during the pressure stroke to the displacement leads to an overpressure in the pumping chamber that gets through reduces the fluid movement through the outlet valve.

    From this state, the exhaust valve 64 is closed and the intake valve 62 is opened. Subsequently the pumping membrane 14 is moved upward by the actuation of the piezoelectric element 24 is terminated. The thereby expanding Pumping chamber leads to a negative pressure in the pumping chamber, in turn, a suction of fluid through the open Inlet valve 62 has the consequence. Subsequently, will the inlet valve 62 is closed and the outlet valve 64 is opened, so that again reaches the above-mentioned initial state is. By the described pumping cycle would thus a volume of fluid substantially equal to the stroke volume of the Diaphragm section 14 corresponds, from the fluid channel 54 to the fluid channel 56 is pumped.

    According to the invention as piezo actuators preferably piezo-membrane transducers or piezo bending transducer used. An optimal Hub performs such a bending transducer when the lateral dimensions of the piezoceramic about 80% of the underlying Correspond membrane. Depending on the lateral dimensions the membrane, which typically has side lengths of 4 mm to 12 mm, can thus deflections of several 10 μm stroke and thus volume strokes in the range of 0.1 μl to 10 μl. Preferred embodiments The present invention has volume strokes at least in such an area, as in such an area Volume stroke advantageous bubble tolerant peristaltic pumps can be realized.

    It should be noted in piezo membrane transducers that this an effective stroke only down, d. H. to the pump body towards. In this regard is on the schematic Representations of Fig. 2a to 2f referenced. Fig. 2a shows a piezoceramic 100 on both surfaces the same is provided with metallizations 102. The piezoceramic preferably comprises a large d31 coefficient and is polarized in the direction of arrow 104 in FIG. 2a. According to Fig. 2a, no voltage is applied to the piezoceramic.

    To produce a piezo-membrane transducer is now in Fig. 2a shown piezoceramic 100 fixed on a membrane 106 mounted, for example glued, as shown in Fig. 2b is. The illustrated membrane is around a silicon membrane, but with the membrane may be formed by any other materials, as long as they can be contacted electrically, for example as a metallized silicon membrane, as a metal foil or made conductive by a two-component injection molding Plastic membrane.

    If a positive voltage is applied to the piezoceramic, i. H. a voltage in polarization direction, U> 0, applied, so contracts the piezoceramic, see Fig. 2c. By the solid Connection of the piezoceramic 100 to the membrane 106 is by this contraction the membrane 106 deflected downwards, as illustrated by arrows in Fig. 2d.

    In order to effect a movement of the membrane upwards, would have a negative voltage, d. H. a tension against the Polarization direction, are applied to the piezoceramic, as shown in Fig. 2e. However, this leads to a depolarization the piezoceramic even at low field strengths in the opposite direction, as in Fig. 2e by an arrow 108th is indicated. Typical depolarization field strengths of Lead zirconate titanate ceramics (PZT ceramics) are, for example at -4000 V / cm. Thus, a movement of the Membrane upwards, d. H. in the direction of the piezoceramic, can not be realized, as indicated in Fig. 2f.

    Despite this drawback to the effect that due to the asymmetrical nature of the piezoelectric effect with the two-layer silicon piezoelectric bending transducer, ie the piezo diaphragm transducer, only an active downward movement, ie toward the pump body out, can be realized, is the use Such a bending transducer is a preferred embodiment of the present invention, since this form of transducer has numerous advantages. First, they have a fast response, on the order of about 1 millisecond with low power consumption. Furthermore, a scaling with dimensions of piezoceramic and membrane over large areas is possible, so that a large stroke (10 .... 200 microns) and a large force (switching pressures 10 4 Pa to 10 6 Pa) are possible, with a larger Hub decreases the achievable force and vice versa. Furthermore, the medium to be switched is separated from the piezoceramic by the membrane.

    If the peristaltic micropumps of the invention are to be used in applications where bubble-tolerant, self-priming behavior is required, the micro-peristaltic pumps must be designed to comply with a compression ratio design rule that defines the ratio of stroke volume to dead volume. For the definition of the terms displacement volume .DELTA.V and dead volume V 0 , reference is first made to FIGS. 3a to 3b.

    Fig. 3a shows schematically a pump body 200 with a the upper surface thereof, in which a pumping chamber 202 is structured. Above the pump body 200 is schematic a membrane 204 shown with an inlet valve piezoelectric actuator 206, a pumping chamber piezoelectric actuator 208 and a Exhaust valve piezoelectric actuator 210 is provided. By the Piezoactuators 206, 208 and 210 may be respective areas of the Membrane 204 down, d. H. towards the pump body 200 to be moved, as shown by arrows in Fig. 3a is shown. Through the line 212 is in Fig. 3a also the the pumping chamber 200 opposite portion of the membrane 204, d. H. the pumping membrane, in its deflected, d. H. actuated by the pumping chamber piezoactuator 208, state shown. The difference of the pumping chamber volume between the undeflected state of the diaphragm 204 and the deflected State 212 of diaphragm 204 represents the stroke volume ΔV of the pumping membrane.

    According to Fig. 3a, the under the intake valve piezoelectric actuator 206 and disposed below the exhaust valve piezoelectric actuator 210 Channel areas 214 and 216 by a respective actuation of the corresponding piezoelectric actuator are closed by the respective membrane areas on the underlying Resting areas of the pump body. Here are the figures 3a to 3c only rough schematic representations, wherein the respective elements are configured such that a Closing respective valve openings is possible. Consequently are in turn an inlet valve 62 and an exhaust valve 64th educated.

    In Fig. 3b, a situation is shown in which the volume of the pumping chamber 202 is reduced by operating the pumping chamber piezoelectric actuator 208 and in which the inlet valve 62 is closed. The situation shown in Fig. 3b thus represents the state after the discharge of a fluid amount from the exhaust valve 64, wherein the volume of the remaining between the closed inlet valve 62 and the passage opening of the open exhaust valve 64 fluid area represents the dead volume V 0 with respect to the pressure stroke, such as is shown by the hatched area in Fig. 3b. The dead volume with respect to a suction stroke in which the inlet valve 62 is opened and the outlet valve 64 is closed is defined by the volume of the fluid area remaining between the closed outlet valve 64 and the passage opening of the open inlet valve 62, as shown in Fig. 3c by the hatched area is.

    It should be noted at this point that the respective dead volume is defined by the respective closed valve up to the passage opening at which a significant pressure drop occurs at the moment of a respective change in volume of the pumping chamber. With a symmetrical construction of inlet valve and outlet valve, as is preferred for a bidirectional pump, the dead volumes V 0 for the pressure stroke and the suction stroke are identical. If different dead volumes occur due to an asymmetry for a pressure stroke and a suction stroke, then, in the sense of a worst-case analysis, it is assumed in the following that the larger of the two dead volumes is used to determine the respective compression ratio.

    The compression ratio of the micro-peristaltic pump is calculated from the stroke volume ΔV and the dead volume V 0 as follows: ε = ΔV / V 0 ,

    The following is based on a worst-case view, at the entire pump area with a compressible Fluid (gas) is filled. The case of a peristaltic Pump cycle, as described above, in the Peristaltic pump occurring volume / pressure conditions are shown in the diagram of Fig. 4. In this case, in Fig. 4 in each case both the isothermal volume / pressure curves as also shown the adiabatic volume / pressure characteristics, being in the sense of a worst-case consideration in the following of isothermal conditions, as in slow state changes occur, is assumed.

    At the beginning of a pressure stroke, there is a pressure p 0 in the fluid area existing between the inlet valve and the outlet valve, while this area has a volume V 0 + ΔV. Starting from this state, the pressure membrane moves during the pressure stroke to the stroke volume .DELTA.V down, creating an overpressure p Ü in the fluid region, ie the pumping chamber forms, so that at a volume of V 0, a pressure of p 0 + p Ü prevails. The overpressure in the pumping chamber degrades by the air volume .DELTA.V is conveyed through the outlet until a pressure equalization has taken place. This outflow of fluid from the outlet in Fig. 4 corresponds to the jump from the upper curve to the lower curve. At the end of the pressure equalization there is therefore a state p 0 , V 0 , which corresponds to the starting point of a suction stroke. Starting from this state, the membrane is moved away from the pump body, ie the volume of the pressure chamber expands by the displacement volume .DELTA.V. Thus, the state referred to in Fig. 4 as "suction stroke after expansion" p 0 - p u , V 0 + ΔV is changed. Due to the prevailing negative pressure, a fluid volume .DELTA.V is sucked through the inlet port until a pressure equalization has taken place. The inflow of fluid into the pumping chamber corresponds in Fig. 4 to the jump from the lower curve to the upper curve. After pressure equalization, the state p 0 , V 0 + ΔV prevails, which in turn corresponds to the starting point of a pressure stroke.

    In the above general state considerations, which refer to general explanation of the invention were, respectively the volume displacements of the intake valve and exhaust valve between the respective suction strokes and pressure strokes neglected.

    In order to achieve a bubble tolerance, the overpressure p Ü during the pressure stroke, and the negative pressure p U during the suction stroke, a minimum value must exceed or fall below during the pressure stroke during the intake stroke. In other words, the pressure amount during the compression stroke and the suction stroke must exceed a minimum value, which may be referred to as delivery pressure p F. This delivery pressure is the pressure in the pressure chamber which must at least prevail to move past a liquid / gas interface at a location which is a flow point between the pump chamber and the passage opening of the first or second valve, including this passage opening. This delivery pressure can be determined as follows, depending on the size of this flow point.

    Capillary forces must be overcome if free surfaces, for example in the form of gas bubbles (eg air bubbles), are moved in the fluid areas within the pump. The pressure that must be applied to overcome such capillary forces depends on the surface tension of the liquid at the liquid / gas interface and the maximum radius of curvature r 1 and the minimum radius of curvature r 2 of the meniscus of that interface:

    Figure 00150001

    The delivery pressure to be provided is defined by Equation 2 at the location within the flow path of the microperistaltic pump where the sum of the inverse radii of curvature r 1 and r 2 of a liquid / gas interface having a given surface tension is at a maximum. This point corresponds to the Flußengstelle.

    Illustratively, for example, a channel 220 (Fig 5a) viewed with a width d, wherein the height of the Channels also d. The channel 220 has at both Channel ends 222, for example, under the valve diaphragm or the pumping membrane, a change in cross section. In Fig. 5a the channel is completely filled with a liquid 224, which flows in the direction of the arrow 226.

    According to FIG. 5 b, an air bubble 228 now encounters the change in cross section at the entrance of the channel 220. In this case, a wetting angle  occurs. The wetting angle  defines a maximum radius of curvature r 1 and a minimum radius of curvature r 2 of a meniscus 230 to be moved through the channel 220, with r 1 = r 2 for the same height and width of the channel. FIG. 5 c illustrates the situation when the air bubble or meniscus 230 reaches the change in cross section 222 at the end of the channel 220.

    If such a channel represents the area of a fluid system at which the greatest capillary force must be overcome, the required pressure in this special case is r 1 = r 2 = r = d / 2: Δp = σ 2 r = σ 4 d

    This pressure barrier is not negligible in microperistaltic pumps of the type according to the invention due to the small dimensions of geometry, if such a channel represents the bottleneck of the pump. With a line diameter of for example d = 50 μm and a surface tension air / water of σ wa = 0.075 N / m, the pressure barrier Δp b = 60 hPa, while with a channel diameter d = 25 μm the pressure barrier Δp b = 120 hPa.

    In the case of microperistaltic pumps of the type according to the invention, however, the mentioned constriction is generally defined by the distance between the valve membrane and the opposite region of the pump body (for example a sealing lip) when the valve is open. This bottleneck represents a gap having an infinite width compared to the height, ie r 1 = r and r 2 = infinity.

    For such a channel it follows from equation 2 above: Δp = σ 1 r

    In general, the relationship between the smallest radius of curvature and the smallest wall distance d is given by the following relationship: r = d 2 · sin (90 ° + Γ - Θ) where Θ represents the wetting angle and Γ the tilt between the two walls.

    The worst-case case, ie the smallest radius of curvature independent of the tilt angle and wetting angle, is given if the sine function is maximal, ie sin (90 ° + Γ-Θ) = 1. This occurs, for example, in abrupt cross-sectional changes, as shown in FIGS. 5a to 5c, or in combinations of tilt angle Γ and wetting angle Θ. In the worst case case: r = d 2

    The smallest occurring radius of curvature can therefore be independent from the tilt angle Γ, wetting angle Θ or abrupt cross-sectional changes half the smallest be aufetwenden wall distance.

    In a peristaltic pump, fluid connections exist between the chambers with a given channel geometry and a constriction defining a minimum flow dimension d. For such a channel: Δp = σ 4 d

    On the other hand, the peristaltic pump has a constriction at the inlet or outlet valve, which is defined by the gap geometry dependent on the valve lift d. For these applies: Δp = σ 2 d

    The respective bottleneck (channel narrowing or valve throat in the opened state), at the larger capillary forces must be overcome, as Flußengstelle the Mikroperistaltikpumpe to be viewed as.

    In preferred embodiments of the present invention are therefore connecting channels within the peristaltic pump designed so that the diameter of the channel at least twice the valve throat, i. the Distance between diaphragm and pump body in open Valve state, exceeds. In such a case, the Valve gap the Flußengstelle the Mikroperistaltikpumpe For example, at a valve lift of 20μm Connecting channels with a smallest dimension, i. Bottleneck, be provided by 50μm. The upper limit of the Channel diameter is determined by the dead volume of the channel.

    The capillary force to be overcome depends on the surface tension at the liquid / gas interface. These Surface tension in turn depends on the involved Partners. For a water / air interface is the Surface tension about 0.075 N / m and slightly varies with the temperature. Organic solvents usually possess a significantly lower surface tension while the Surface tension at a mercury / air interface for example, about 0.475 N / m. A peristaltic pump, which is designed to withstand the capillary force at a surface tension of 0.1 N / m is thus suitable Bubble-tolerant to almost all known liquids and gases and self-priming to pump. Alternatively, you can the compression ratio of a Mikroperistaltikpumpe invention be made higher accordingly to one to allow such pumping, for example, for mercury.

    The design rules discussed below apply to the Promotion of gases and incompressible liquids, wherein assumed in the promotion of liquids must be that in the worst case, air bubbles the entire Fill pump chamber volume. In the extraction of gases must be expected that due to a condensation Liquid can get into the pump. Hereinafter It is assumed that the piezoelectric actuator designed this way is that all the required negative pressures and pressures reached can be.

    First, consider a pressure stroke. During the ejection process, the actuator membrane compresses the gas volume or air volume. The maximum overpressure in the pump chamber p Ü is then determined by the pressure in the air bubble. It is calculated from the equation of state of the bubble. p 0 (V 0 + ΔV) γ A = (p 0 + p Ü ) (V 0 ) γ A The variables p 0 , V 0 , ΔV and p ü were explained above with reference to FIG. 4. γ A represents the adiabatic coefficient of the gas, ie the air. The left side of the above equation represents the state before compression, while the right side represents the state after compression. Furthermore, the overpressure p Ü must be greater than the positive delivery pressure p F during the pressure stroke: p Ü > p F

    Now consider a suction stroke. The suction stroke differs by the initial position of the volumes. After expansion, the negative pressure p U arises in the pumping chamber, ie p U is negative: p 0 V 0 γ A = (p 0 + p U ) (V 0 + ΔV) γ A

    The left side of Equation 11 represents the state before expansion, while the right side represents the state after expansion. The negative pressure p U during the pressure stroke must be smaller than the necessary negative delivery pressure p F. It should be noted that the discharge pressure p F in terms of absolute value in the consideration of the pressure stroke, in terms of absolute value in the consideration of the suction stroke. It follows: p U <p F

    From the above equations results for the minimum required compression ratio of bubble-tolerant microperistaltic pumps for the pressure stroke: ε> p 0 p 0 + p F 1 γ A - 1

    For the suction stroke the following compression ratio results: ε> p 0 p 0 + p F 1 γ A - 1

    If the delivery pressure p F is small compared to the atmospheric pressure p 0 , the preceding equations can be simplified as follows, which corresponds to a linearization around the point p 0 , V 0 :

  • compression stroke: ε> 1 γ A p F p 0
  • suction stroke: ε> - 1 γ A p F p 0
  • As a valid equation for the suction stroke and the pressure stroke results: ε> 1 γ A p F p 0

    For fast state changes, the ratios are adiabatic, ie γ A = 1.4 for air. For slow state changes, the ratios are isothermal, ie γ A = 1. With a consistent application of the worst-case assumption, the criterion with γ A = 1 is used below. Thus, as a design rule for the necessary compression ratio of bubble-tolerant micro-peristaltic pumps, it can be stated that the compression ratio must be greater than the ratio of the delivery pressure to the atmospheric pressure, ie: ε> p F p 0

    Or with the mentioned volumes: .DELTA.V V 0 > p F p 0

    The simple linear design rule given above corresponds to the tangent to the isothermal equation of state of FIG. 4 at point p 0 , V 0 .

    Preferred embodiments of microperistaltic pumps according to the invention are thus designed so that the compression ratio satisfies the above condition, wherein the minimum necessary delivery pressure as defined in Equation 8 Pressure equals when occurring in the peristaltic pump Kanalengstellen have minimal dimensions, the at least twice the size of the valve gap. alternative can the minimum required delivery pressure in the Equation 3 or Equation 7 defined pressure correspond, if the Flußengstelle the microperistaltic pump is not is defined by a gap but a channel.

    If a microperistaltic pump according to the invention is to be used when pressure boundary conditions of a negative pressure p 1 at the inlet or a counterpressure p 2 prevail at the outlet, the compression ratio of a microperistaltic pump must be correspondingly greater in order to allow pumping against these inlet pressures or outlet pressures. The pressure boundary conditions are defined by the intended application of the microperistaltic pump and can range from a few hPa to several 1000 hPa. For such cases occurring in the pumping chamber pressure p T, or negative pressure must reach p U these back pressures at least, so that a pumping action occurs. For example, only the height difference of a possible inlet vessel or outlet vessel of 50 cm in water leads to counter pressures of 50 hPa.

    Furthermore, the desired delivery rate is a constraint which makes additional demands. For a given Stroke volume .DELTA.V is the delivery rate Q by the operating frequency f of the repetitive peristaltic cycle defines: Q = ΔV · f. Within the period T = 1 / f must have both the suction stroke and the pressure stroke of the peristaltic pump be performed, in particular, the stroke volume ΔV be implemented. The available time is therefore maximum T / 2 for suction stroke and pressure stroke. The needed Time to the stroke volume through the pumping chamber inlet and to promote the Ventilengstelle now depends on the one hand the flow resistance, on the other hand from the pressure amplitude in the pumping chamber.

    Should with a Mikroperistaltikpumpe invention Foamy substances can be pumped, so it may be necessary be that a plurality of capillary forces, like them described above, must be overcome, as several corresponding liquid / gas interfaces occur. In In such a case, the micro-peristaltic pump must be designed be to have a compression ratio to accordingly To produce higher discharge pressures.

    In summary, it can be determined that the compression ratio of a microperistaltic invention must be appropriately higher when necessary in the microperistaltic delivery pressure p F also depends in addition to the aforementioned capillary forces on the boundary conditions of the application. It should be noted that here the delivery pressure is considered relative to the atmospheric pressure, that is, a positive delivery pressure p F is assumed in the pressure stroke, while a negative delivery pressure p F is assumed in the intake stroke. As a technically meaningful value for a robust operation, therefore, an amount of the delivery pressure of at least p F = 100 hPa can be assumed for a suction stroke and a pressure stroke.

    Considering a back pressure of, for example, 3000 hPa at the pump outlet, against which must be pumped, so gives According to the above equation 13, a compression ratio of ε> 3, assuming an atmospheric pressure of 1013 hPa becomes.

    Must the Mikroperistaltikpumpe against a large vacuum suck in, for example, a negative pressure of -900 hPa, so is a compression ratio according to the above equation 14 from ε> 9 to a pump against such To allow negative pressure.

    Examples of peristaltic micropumps that the realization allow such compression ratios will be explained in more detail below.

    Fig. 6b shows a schematic cross-sectional view of a peristaltic micropump with membrane element 300 and pump body 302 along the line b-b of Fig. 6a and Fig. 6c, while Fig. 6a is a schematic plan view of the Membrane element 300 and Fig. 6c is a schematic plan view on the pump body 302 shows. The membrane element 300 has again three membrane sections 12, 14 and 16, the are each provided with piezo actuators 22, 24 and 26. In the pump body 302 is in turn an inlet port 32 and an outlet opening 34 is formed, such that the inlet opening 32 together with the membrane portion 12 an inlet valve defined while the outlet opening 34 with the membrane area 16 defines an exhaust valve. Below the membrane section 14 is a pumping chamber 304 in the pump body 302 formed. Further, fluid channels 306 are in the pump body 302 formed with the membrane areas 12 and 16 associated valve chamber 308 and 310 fluidly connected are. The valve chambers 308 and 310 are shown in the FIG Embodiment by recesses in the membrane element 300, wherein in the membrane element 300 further a recess 312 contributing to the pumping chamber 304 is formed is.

    In the embodiment shown in Figs. 6a to 6c the pumping chamber volume 304 is made larger than the volume the valve chambers 308 and 310. This is shown in the Embodiment achieved by a pumping chamber lowering in which a structuring in the form of a Pumping chamber lowering is formed in the pump body 302. The stroke of the pumping membrane 14 is preferably designed to that they largely the volume of the pumping chamber 304 can displace.

    A further increase in the pumping chamber volume compared to Valve chamber volume is in that shown in Figs. 6a to 6c Embodiment achieved by the pumping chamber membrane 14 in terms of area (in the plane of the membrane element 300 and the pump body 302) is designed to be larger than the valve chamber membranes, as best seen in Fig. 6a is. Thus, there is an area compared with the valve chambers larger pumping chamber.

    To the flow resistance between the valve chambers 308th and 310 and the pumping chamber 304 are the supply passages 306 in the surface of the pump body 302 structured. These fluid channels 306 provide a reduced Flow resistance, without the compression ratio significantly degrade the peristaltic micropump.

    As an alternative to the embodiment shown in FIGS. 6a to 6c could be the surface of the pump body 302 be realized with three-stage subsidence to the pumping chamber increased depth (compared to the valve chambers) implement while the top chip is essentially one unstructured membrane is. Such two-stage reductions are technologically more difficult to implement than that in the Fig. 6a to 6c embodiment shown.

    Exemplary dimensions of the embodiment of a peristaltic micropump shown in FIGS. 6a to 6c are as follows:

  • Valve diaphragm dimensions 12, 16: 7.3 x 5.6 mm;
  • Measurement of the pumping membrane 14: 7.3 x 7.3 mm;
  • Membrane thickness: 40 μm;
  • Diameter of the inlet or outlet nozzle 32, 34: at least 50 pm;
  • Valve chamber height: 8 μm;
  • Height of the pumping chamber: 30 μm;
  • Width of the valve sealing lips d DL : 10μm;
  • Total realized size: 8 x 21 mm;
  • Dimensions of the piezo elements: Area: 0.8 times membrane dimension, thickness: 2.5 times membrane thickness;
  • Thickness of the piezo elements: 100μm; and
  • Opening cross-section of the openings 32, 34: 100μm x 100μm.
  • An enlarged view of the left part of FIG. 6b is shown in FIG. 7, wherein in Fig. 7, the height H of the Pümpkammer 304 is displayed is. Although, as shown in Fig. 7, the pumping chamber 304 forming structuring in the pump body 302 and in the membrane element 300 have the same depths, it is preferred that structuring in the pump body 302 with a greater depth than that in the membrane element to provide the flow channel 306 with sufficient River cross section to provide, but without the compression ratio overly impaired. For example For example, the structurings in the pump body 302 that belong to the fluid channel 306 and the pumping chamber 304 contribute a Depth of 22 microns, while the structuring in the membrane element 300 defining the valve chambers 308 contribute to the pressure chamber 304, a depth of 8 may have .mu.m.

    Fig. 8 shows a schematic cross-sectional view of a Enlargement of the section A of Fig. 7, but in one modified form. According to Fig. 8, the bridge of the Opening 32 spaced toward the channel 206 arranged. This allows mounting tolerances in a double-sided Lithography to be considered. Furthermore, can to prevent wafer thickness variations, the Valve openings with different cross-sectional sizes for Can have no adverse effects. As can be seen in Fig. 8, defines the distance x to the Membrane 12 the Flußengstelle between the pumping chamber and valve port with open valve position.

    As stated above, in the areas of the fluid system, in which a pumping action is required by a pumping chamber volume of a peristaltic pump is formed, the compression ratio of the peristaltic pump is large be a self-filling behavior and a to ensure robust operation with respect to a bubble tolerance. To achieve this, it is preferable to have the dead volumes to keep small, which can be supported by the contour or shape of the pumping chamber to the bending line of the Pumping membrane is adapted in the deflected state.

    A first way to realize such an adaptation is to implement a round pumping chamber, i.e. a pumping chamber whose peripheral shape to the deflection the pumping membrane is adapted. A schematic Top view of the pumping chamber and fluid channel section of a Pump body with such a pumping chamber is shown in Fig. 9a shown. In the round pumping chamber 330 open again comparable to the representation of Fig. 6c, the fluid channels 306, which fluidly connects to valve chambers, for example again structured in a membrane element can be produced.

    To further reduce the dead volume and thus a achieve further increase of the compression ratio To be able to, the pumping chamber under the pumping membrane can do so be designed that their pump diaphragm facing contour Precisely following the bending line of the pumping membrane. A Such contour of the pumping chamber, for example, by a correspondingly shaped injection molding tool or by a Embossing stamp can be achieved. A schematic plan view on a pump body 340, in which such a bending line the actuator membrane, the following fluid chamber 342 structured is shown in Fig. 9b. Further, in Fig. 9b in the Pump body structured fluid channels 344 shown, the lead to the fluid chamber 342 toward and away from the same. A schematic cross-sectional view along the line c-c of Fig. 9b is shown in Fig. 9c, wherein in Fig. 9c further a diaphragm 346 with the same associated piezoelectric actuator 348 shown. A flow through the fluid channels 344 is in Fig. 9c indicated by arrows 350. Further, in Fig. 9c the membrane 346 facing the bending line of the membrane (in the actuated state) adapted contour 352 of the fluid chamber or pumping chamber 342 to recognize. This form of fluid chamber 352 allows that upon actuation of the diaphragm 346th by the piezoelectric actuator 348 substantially the entire volume the fluid chamber 342 is displaced, whereby a high Compression ratio can be achieved.

    An embodiment of a peristaltic micropump, in which both the pumping chamber 342 and valve chambers 360 to the bending lines of the respective associated membrane sections 12, 14 and 16 is adapted in Figs. 10a and Fig. 10b, wherein Fig. 10b is a schematic plan view on the pump body 340, while Fig. 10a a schematic cross-sectional view along the line a-a of Fig. 10b shows. As can be seen from FIGS. 10a and 10b, are shape and contour of the valve chamber 360 and 362 as above Referring to pumping chamber 342, the bending line is explained of the respectively associated membrane section 12 or 16 adapted. As further best seen in FIG. 10b, again, fluid channels 344a, 344b, 344c and 344d are in the Pump body 340 formed. The fluid channel 344a provides a The input fluid channel, the fluid channel 344b connects the Valve chamber 360 with the pumping chamber 342, the fluid channel 344th connects the pumping chamber 342 to the valve chamber 362, and the fluid channel 344d represents an output channel.

    As further shown in Fig. 10a, the membrane element is 380 in this embodiment, an unstructured Membrane element, which in a provided in the pump body 340 Recess is inserted to together with the in The fluid chambers formed the pump body 340, the valve chambers and define the pumping chamber.

    The connection channels 344b and 344c between the actuator chambers are switched so that they are compared to the displacement include low dead volume. Simultaneously reduce these fluid channels between the flow resistance the actuator chambers significantly, so that larger Pümpfrequenzen and thus larger flow rates, one such Current is again indicated by arrows 350 in Fig. 10a, be possible. In the area of the valve chambers 360 and 362 be the fluid channels by operating the membrane sections 12 and 16 through the fully deflected membrane sections separated, so that a fluid separation between the Fluid channels 344a and 344b and between the fluid channels 344c and 344d occurs. The contour of the valve chambers must exactly to the bending line of the respective membrane sections be adapted to achieve a dense fluid separation. Alternatively, as shown in Fig. 11, a Bridge 390 in the respective valve chamber in the area of largest stroke of the diaphragm portion 12 may be provided, the is shaped accordingly, so that it completely through the Bend the membrane portion 12 can be sealed. More specifically, the bridge bends to the edges of the valve chamber towards the top, corresponding to the bending line adapted shape of the valve chamber. This jetty can in the projecting respective valve chamber, wherein alternatively, as it 11, the depth of the connection channels 344 may be greater than the stroke y of the membrane portion 12, in which the membrane section bears against the pump body, so that the bridge 390 is sunk, so to speak. Is the depth the connection channels is greater than the maximum stroke, goes this at the cost of the compression ratio enabled but low flow resistance between the actuator chambers.

    An alternative embodiment of a valve chamber 360 is shown in Fig. 12, where the depth of the connecting channels 344 is smaller than the maximum lift y of the Membrane section 12, and thus as the depth of the Bend line of the diaphragm portion 12 adapted valve chamber 360 in the region of the largest stroke of the membrane section 12. This allows a secure seal in the closed state of the valve can be achieved.

    To achieve a valve seal when closed, the given pressure requirements are sufficient, it can be preferred, in the valve chamber 360, a web 390 a not the maximum possible bending line of the Actuator element, d. H. the membrane portion 12 together with the piezoelectric actuator 22, as shown in Fig. 13 is shown. The maximum possible bending line of the membrane section 12 is shown by a dashed line 400 in FIG. 13, while line 410 is the maximum possible deflection of the Membrane portion 12 due to the provision of the web 390 a equivalent. Thus, the membrane 12 sits in fully deflected Condition when the web 390 is sealed, with a Residual force on the web 390a, this residual force dimensioned can be used to print requests that the Seal must endure to suffice.

    In practical realizations, the bending line of the Membrane often not perfectly concentric to the membrane center be, for example due to mounting tolerances the piezoceramics and due to inhomogeneities of the Glue application, through which the piezoceramics on the membranes are attached. Therefore, the area of the web seal something, for example, around 5 to 20 microns, depending on the stroke of the actuator, be increased over the rest of the fluid chamber, for a secure contact of the membrane with the web and thus ensuring a secure seal. This matches with also the situation shown in Fig. 13. To note, however, that thereby increases the dead volume and the compression ratio is reduced.

    As an alternative to the mentioned possibilities, fluid chamber material may be used at least in the area under the moving Membrane a plastically deformable material, for example Silicone, to be used. By appropriately sized Actuator forces can then be compensated for inhomogeneities become. In such a case, there is no hard-hard seal more before, so that a certain tolerance against particles and deposits exists.

    In the following, let's take an example of dimensioning a peristaltic pump as shown in Figs. 10a and 10b indicated. The thickness of the membrane sections 12, 14 and 16 and thus the thickness of the membrane element 380 can For example, 40 microns, while the thickness of the piezoelectric actuators may be for example 100 microns. As a piezoceramic can be a PZT ceramic with a large d31 coefficient be used. The side length of the membranes can For example, be 10 mm, while the side length of Piezo actuators may be 8 mm, for example. The voltage swing for actuating the actuators in the aforementioned actuator geometry can be for example 140 V, which is a maximum Stroke of approx. 100 to 200 μm with a stroke volume of Pumping membrane of about 2 to 4 ul result.

    By adapting the fluid chamber design to the bend line the membrane drops the dead volume of the three for the peristaltic pump needed fluid chambers away, so that only the connecting channels connecting the valve chambers with the pumping chamber connect, remain. Become connecting channels with a depth of 100 microns, a width of 100 microns and a Length of 10 mm, so that a total length for gives the fluid channels 344b and 344c of 20 mm, gives the a pumping chamber dead volume of 0.2 μl. This can be a compression ratio ε = ΔV / V = 4 μl / 0.2 μl = 20 determined become.

    With such a large compression ratio of up to 20, such fluid modules are bubble tolerant and self-priming and can deliver both liquids and gases. Such fluid pumps can also be used for compressible and liquid media basically build up several bar pressure, depending on the design of the piezoelectric actuator. In such a micropump the maximum pressure that can be generated is no longer limits the compression ratio, but by the maximum Force of the drive element and the tightness the valves defined. Despite these properties can by a suitable channel dimensioning with a low Flow resistance can be promoted several ml / min.

    In the embodiment described above, all were Fluid channels, d. H. also the inlet fluid passage 344a and the outlet fluid channel 344d is guided laterally, d. H. the fluid channels run in the same plane as the fluid chambers. As stated above, in such a Course the sealing of the channels be difficult. Advantageous on the lateral course of the fluid channels, however, that the entire fluid system including with the inlet channel 344a and / or the outlet channel 344d connected reservoirs can be formed with a manufacturing step, for example by injection molding or embossing.

    In Fig. 14 is an embodiment of an inventive Microperistaltic pump shown in which the inlet fluid channel 412 and the outlet fluid passage 414 in the pump body 340 vertically sunk. The fluid channels 412 and 414 have a substantially vertical portion 412a and 414a, each substantially centrally located below the associated Diaphragm sections 12 and 16 in the valve chambers 360 and 362, respectively. The advantage of the one shown in FIG Embodiment of the fluid channels is that the fluid channels can be sealed defined. The disadvantage, however, is that such vertically submerged fluid channels Manufacturing technology are difficult to produce.

    The peristaltic micropumps according to the invention are preferably driven by the membrane, for example the metal membrane or the semiconductor membrane, on one Ground potential, while the piezoceramics by a typical peristaltic cycle are moved by each corresponding voltages applied to the piezoceramics become.

    In addition to the microperistaltic pump described above Use of three fluid chambers 342, 360 and 362 may be According to the invention peristaltic micropump further fluid chambers have, for example, a further fluid chamber 420, which via a fluid passage 422 with the pumping chamber 342 connected is. Such a structure is schematic in FIG shown, wherein a first reservoir 424 via the Fluid passage 344a is connected to the valve chamber 360, a second reservoir 426 via a fluid passage 428 with the Valve chamber 420 is connected and a third reservoir 430 is connected to the valve chamber 362 via the fluid passage 344d is.

    A structure with four fluid chambers, as shown in FIG is, for example, a branching structure or form a mixer in which the mixed streams are active can be promoted. The extension to four fluid chambers with four associated fluid actuators, such as for example, shown in Fig. 15, the realization of three peristaltic pumps, each pumping direction between all reservoirs 424, 426 and 430 realized in both directions can be. It is possible that a single Membrane element covers all fluid chambers and reservoir container, wherein for each fluid chamber a separate piezoelectric actuator is provided. Thus, the entire fluidics can be very flat be designed, with the functional, fluidic Structures including fluid chambers, channels, membranes, piezoactuators and support structures an overall height of the order of magnitude 200 to 400 microns may have. Thus, systems are conceivable that can be integrated into smart cards. Furthermore, even flexible fluidic systems are conceivable.

    In addition to the embodiments shown, fluid chambers be interconnected in any plane. So can for example, different reservoirs z. B. one each Microperistaltic be assigned, which then, for example Reagents to a chemical reaction (For example, in a fuel cell), or a calibration sequence for an analysis system, for example in a water analysis.

    To produce a piezo-membrane converter, the piezoceramics for example, to the respective membrane sections to be glued. Alternatively, the piezoceramics, For example, PZT, applied directly in thick film technology be, for example by screen printing with suitable intermediate layers.

    An alternative embodiment of an inventive microperistaltic pump with recessed inlet fluid channel 412 and recessed outlet fluid channel 414 is shown in FIG. 16 shown. The inlet flow channel 412 again opens substantially centrally under the membrane section 12 in a Valve chamber 442, while the Auslaßfluidkanal 414 substantially centrally under the membrane portion 16 in a Valve chamber 444 opens. The respective mouth openings the inlet channel 412 and the outlet channel 414 are provided with a Sealing lip 450 provided. Further, in the pump body 440 a pumping chamber 452 formed by fluid channels in Walls 454 with the valve chambers 442 and 444 fluidly connected is. According to the embodiment shown in Fig. 16 form the three membrane sections 12, 14 and 16th in turn, a membrane element 456. In this embodiment However, the membrane sections are by piezo stack actuators 460, 462 and 464 driven on the corresponding Membrane sections can be placed. To this end the piezo stack actuators are using appropriate Housing parts 470 and 472, in Fig. 16 away from the Pump body and the membrane element are shown used.

    Piezostapelaktoren are advantageous in that the same not be firmly connected to the membrane element so that they allow a modular design. In such not fixedly connected piezo stack actuators the actuators do not actively retract a membrane section, when an operation of the same is terminated. Much more can a return movement of the membrane portion only by the Restoring force of the elastic membrane itself done.

    The peristaltic micropumps according to the invention can using a variety of manufacturing materials and manufacturing techniques are manufactured. The pump body can be made of silicon, for example, made of plastic by injection molding or precision engineering produced by machining. The membrane element, the drive diaphragm for the two valves and forms the pumping chamber can be made of silicon, Can through a metal foil, such as stainless steel or titanium, may be formed by a two-component injection molding technique manufactured with conductive coatings provided plastic membrane may be formed, or may be realized by an elastomeric membrane.

    The connection between the membrane element and the pump body is an important point since high shear forces can occur at this connection during operation of the peristaltic pump. The following requirements apply to this connection:

    • thick;
    • thin bonding layer (<10 μm), since the pump chamber height is a critical design parameter that affects the dead volume;
    • mechanical resistance; and
    • chemically resistant to media to be conveyed.

    In the case of silicon as a basic structure and membrane element A non-silicone Silicon Fusion Bonding can be used. In the case of a silicon-glass combination may preferably Anodic bonding can be used. More options are a eutectic wafer bonding or a wafer life.

    If the basic structure is made of plastic and the Membrane element is a metal foil, can be a lamination be performed when a bonding agent between membrane element and basic structure is used. alternative may be gluing with a high shear adhesive take place, in which case in the basic structure preferably Kapillarstopgräben be formed to prevent penetration To avoid adhesive in the fluid structure.

    If both membrane element and pump body off Plastic can be used to connect the same ultrasonic welding be used. If one of the two Structures is optically transparent, can alternatively laser welding respectively. In the case of an elastomeric membrane can the sealing properties of the membrane are also used be to ensure a seal by clamping.

    The following briefly explains how a possible attachment the membrane on the pump body in an inventive Microperistaltic pump can be done. Is at the micropump according to the invention, the membrane to the pump body glued, it should be noted that the dosage of Fügeschichtmaterialien (such as adhesive) is critical because on the one hand, the membrane must be completely tight (that is, sufficient Adhesive must be applied), and on the other hand penetration of excess adhesive into the fluid chambers must be avoided.

    The bonding layer material that is an adhesive or an adhesive may be e.g. by dispensing or by a correspondingly shaped stamp on the joining layer applied. After the order of the joining material is the membrane fitted to the base body. Possible burrs, the e.g. when singulating at the edge of the membrane, find a place for the ridge, so that a defined position of the membrane especially in the Direction perpendicular to the surface of the same ensured is what matters in terms of dead volume and tightness is.

    Then it is pressed with a stamp on the pump body, so that the adhesive layer is as thin and defined remains. To take up excess adhesive, a capillary stop trench may be used be provided, which in the pump body surrounds formed fluid areas. Thus, such excess Glue does not get into the fluid chambers. Under these conditions, the adhesive can be defined and cure thinly. The curing can be carried out at room temperature or accelerated in the oven or by UV irradiation when using UV-curing adhesives.

    As an alternative to the adhesive technique described can be used as a connection technique a solving of the main body or pump body by suitable solvents and a joining of a Plastic membrane to the main body done.

    Claims (18)

    1. Peristaltic micropump comprising:
      a first membrane region (12) with a first piezo-actor (22; 460) for actuating the first membrane region;
      a second membrane region (14) with a second piezo-actor (24; 462) for actuating the second membrane region;
      a third membrane region (16) with a third piezo-actor (26; 464) for actuating the third membrane region; and
      a pump body (30; 302; 340; 440),
      wherein the pump body forms, together with the first membrane region (12), a first valve (62) whose passage opening (32) is open in the non-actuated state of the first membrane region and whose passage opening may be closed by actuating the first membrane region,
      wherein the pump body forms, together with the second membrane region (14), a pumping chamber (42; 304; 330; 342; 452) whose volume may be decreased by actuating the second membrane region, and
      wherein the pump body forms, together with the third membrane region (16), a second valve (64) whose passage opening (34) is open in the non-actuated state of the third membrane region and whose passage opening may be closed by actuating the third membrane region,
      wherein the first and second valves (62, 64) are fluidically connected to the pumping chamber.
    2. Peristaltic micropump of claim 1, wherein between a stroke volume ΔV a dead volume V0, a delivery pressure PF, and the atmospheric pressure P0 the following relationship applies: ΔV/V0 > PF/P0, wherein the stroke volume ΔV is a volume displaced by an actuation of the second membrane region (14),
      wherein the dead volume V0 is a volume present between the opened passage opening (32; 34) of one of the valves (62, 64) and the closed passage opening (32, 34) of the other of the valves (62, 64) in the actuated state of the second membrane region (14), and
      wherein the delivery pressure pF is the pressure necessary in the pumping chamber (42; 304; 330; 342; 452) to move a liquid/gas interface past a bottleneck in the peristaltic micropump.
    3. Peristaltic micropump of claim 1 or 2, wherein between the first membrane region (12) and the pump body (302; 340; 440) a first valve chamber (308; 360; 442) is formed, and wherein between the third membrane region (16) and the pump body (302; 340; 440) a second valve chamber (310; 362; 444) is formed, wherein the valve chambers are fluidically connected to the pumping chamber (42; 304; 330; 342; 452).
    4. Peristaltic micropump of claim 3, wherein the volume of the pumping chamber (304) is greater than the volume of the first or second valve chamber (308, 310).
    5. Peristaltic micropump of claim 4, wherein a distance between membrane surface and pump body surface in the region of the pumping chamber (304) is greater than in the region of the valve chamber (308, 310).
    6. Peristaltic micropump of claim 4 or 5, wherein the second membrane region (14) and the pumping chamber are greater in area than the first or third membrane region (12, 16) and the associated valve chambers.
    7. Peristaltic micropump of one of claims 3 to 6, wherein the membrane regions (12, 14, 16) are formed in a membrane element (10; 300; 380; 456), wherein the valve chamber (308, 310; 360, 362; 442, 444), the pumping chamber (42; 304; 330; 342; 452), and fluid channels (306; 344) are formed between the valve chambers and the pumping chamber by structures in the pump body and/or the membrane element.
    8. Peristaltic micropump of one of claims 1 to 7, wherein the pumping chamber (330; 342) has a structure in the pump body (340), wherein the contour of the structure is adapted to the arched contour of the second membrane section (14) in the actuated state.
    9. Peristaltic micropump of one of claims 3 to 7, wherein the pumping chamber (342) and the valve chambers (360, 362) have structures in the pump body (340), wherein the contours of the structures are adapted to the respective arched contour of the corresponding membrane section (12, 14, 16) in the actuated state.
    10. Peristaltic micropump of one of claims 1 to 9, wherein the first and the third membrane region (12, 16) and the piezo-actors (22, 26; 460, 464) thereof are designed such that they push on a counter-element (390; 390a) with a predetermined force in the actuated state to close the respective valve.
    11. Peristaltic micropump of claim 9, comprising lateral fluid feed lines (344a, 344b) to the valve chambers (360, 362) formed in the pump body (340), which are closed by actuating the corresponding membrane section.
    12. Peristaltic micropump of claim 11, wherein, in the region of a valve chamber (360, 362), a ridge (390; 390a) is provided against which the corresponding actuated membrane section abuts to close the corresponding lateral fluid line.
    13. Peristaltic micropump of claim 11, wherein the valve chambers comprise, opposite the corresponding membrane section, a plastically deformable material against which the corresponding membrane section abuts in the actuated state.
    14. Peristaltic micropump of one of claims 1 to 13, further comprising at least one further membrane region with a further piezo-actor for actuating the further membrane region, the further membrane region forming, together with the pump body, a further valve whose passage opening is open in the non-actuated state of the further membrane region and whose passage opening may be closed by actuating the further membrane region, the further valve being fluidically connected to the pumping chamber.
    15. Peristaltic micropump of one of claims 1 to 14, wherein the piezo-actors are piezo-membrane converters formed by respective piezo-elements applied onto a membrane region.
    16. Peristaltic micropump of claim 15, wherein the piezo-elements are glued onto the respective membrane region or formed on the respective membrane region in thick film technique.
    17. Peristaltic micropump of one of claims 1 to 14, wherein the piezo-actors are formed by respective piezo-stacks.
    18. Fluid system with a plurality of peristaltic micropumps of one of claims 1 to 17 and a plurality of reservoirs fluidically connected to the peristaltic micropumps.
    EP03792417A 2002-08-22 2003-08-22 Peristaltic micropump Active EP1458977B2 (en)

    Priority Applications (3)

    Application Number Priority Date Filing Date Title
    DE2002138600 DE10238600A1 (en) 2002-08-22 2002-08-22 Peristaltic micropump
    DE10238600 2002-08-22
    PCT/EP2003/009352 WO2004018875A1 (en) 2002-08-22 2003-08-22 Peristaltic micropump

    Publications (3)

    Publication Number Publication Date
    EP1458977A1 EP1458977A1 (en) 2004-09-22
    EP1458977B1 true EP1458977B1 (en) 2005-04-20
    EP1458977B2 EP1458977B2 (en) 2008-11-12

    Family

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    CN1675468A (en) 2005-09-28
    JP4531563B2 (en) 2010-08-25
    EP1458977A1 (en) 2004-09-22
    DE10238600A1 (en) 2004-03-04
    WO2004018875A1 (en) 2004-03-04
    DE50300465D1 (en) 2005-05-25
    EP1458977B2 (en) 2008-11-12
    JP2005536675A (en) 2005-12-02
    US7104768B2 (en) 2006-09-12
    CN100389263C (en) 2008-05-21
    AU2003255478A1 (en) 2004-03-11

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