WO2004018103A1

WO2004018103A1 - Pipetting device and method for operating a pipetting device

Info

Publication number: WO2004018103A1
Application number: PCT/EP2003/006389
Authority: WO
Inventors: Martin Richter; Martin Wackerle; Hans-Jürgen BIGUS; Ralph Debusmann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.; Hirschmann Laborgeräte GmbH & Co. KG
Priority date: 2002-08-22
Filing date: 2003-06-17
Publication date: 2004-03-04
Also published as: AU2003242720A1; AU2003242720A8; DE10238564A1; DE10238564B4; US20050196304A1; EP1531937A1

Abstract

Disclosed is a pipetting device comprising a micropump (200) which is provided with a pump chamber (216) having a first port (222) and a second port (224). Said micropump is also provided with a device (246, 250) for modifying the volume of the pump chamber (216). A first active valve (226) is provided for opening and closing the first port (222) while a second active valve (236) is used for opening and closing the second port (224). The inventive pipetting device further comprises a pipette tip (258) which is connected to the first (222) or second (224) port via a pipette duct.

Description

Pipetting device and method for operating a pipetting device

description

The present invention relates to pipetting devices, and more particularly to pipetting devices with micro pumps.

With increasing improvement in the production of micromechanical structures, diverse devices can now be realized as microstructure devices. Such a microstructure device comprises, for example, a micropipetter device with a micropump.

1 shows a known pipetting device which has a first and second micropump 110a and 110b, which are each constructed from three pump body sections 110, 112 and 114 arranged one above the other. The pump body sections 110, 112 and 114 each comprise a flat disk or wafer with microstructures which are produced by means of suitable etching processes. Typically, the pump body sections 110, 112 and 114 have a semiconductor material such as silicon in such a known micropump. Each of the micropumps 100a and 110b includes a pump chamber 116 formed by boundaries of the pump body portions 110-114. The pump chamber 116 has an inlet opening 118 formed in the lower pump body portion 110. A first flap valve 120, which is designed as a passive check valve, is arranged above the inlet opening 118. The flap valve 120 is formed in the central pump body portion 112 and has an elongated flexible flap 120a that extends across the inlet opening 118. The pump chamber 116 also has an outlet opening 122 which can be closed and opened by a second passive flap valve 124 which is arranged in the pump body section 110. Corresponding to the first flap valve 120, the second flap valve 124 has a flap 124a with an elongated flexible shape.

Furthermore, the micropumps 100a and 100b have a piezoelectric actuating element 126 for changing the volume of the pump chamber 116. The piezoelectric actuating element 126 is arranged as a piezoelectric ceramic layer over a large area on a thin membrane 128 which is arranged flexibly between holding elements. When a suitable voltage is applied to the piezoelectric actuating element 126, the membrane 128 deforms and, depending on the polarity of the voltage, causes the volume of the pump chamber 116 to increase or decrease.

During a suction process, a voltage is applied to the piezoelectric actuating element 126, which deforms the membrane 128 in such a way that there is an increase in the volume of the pump chamber 116. A negative pressure is generated in the pump chamber 116, which causes the valve 120 to change from a closed state to an open state, whereas the valve 124 has a closed state due to the negative pressure. As a result, a fluid is drawn through the opening 118 into the pump chamber 116.

In a pumping operation, the pump chamber volume ^'is reduced by applying an electric voltage to the piezoelectric actuator 116th The resulting excess pressure causes a force to be exerted on the flap valve 124 which moves the flap valve 124 downward. This opens the opening 122, while the inlet opening 118 is closed by the valve 120. By the excess pressure in the pump chamber 116, the fluid is expelled from the pump chamber 116 through the opening 122.

The micropumps 100a and 100b are arranged in the pipetting device in such a way that the micropump 100a on the suction side, i.e. with the inlet opening 118, with a pipette channel 132 of a pipetting tip 134 and on the pressure side, i.e. communicates with the outlet opening 122 to an environment. In contrast, the micropump 100b is connected in the opposite direction to the micropump, so that it is connected on the pressure side to the pipette channel and on the suction side to the surroundings.

When a medium to be dosed is drawn in, the micropump 100a connected on the suction side to the pipette channel is actuated, so that the volume of the pump chamber increases and air is sucked from the pipette channel into the pump chamber. An air cushion 136 in the pipette tip 134 is removed and a dosing medium 138 is sucked into the pipette tip 134. The second micropump 100b, which is connected to the pipette channel on the pressure side, remains switched off.

Conversely, when the aspirated medium is dosed, the micropump 100b is actuated by reducing the volume of the pump chamber thereof, while the micropump 100a remains switched off. The micropump 100b connected on the pressure side to the pipette channel generates an overpressure in the pipette channel, which causes the air cushion 136 to build up and the metering medium to be expelled.

The above-described micropumps 100a and 100b are characterized by simple control, since only the piezoelectric actuating element 126 has to be actuated in the pumping and suction processes as the only active element. A further advantage of the micropumps 100a and 110b is that they can be manufactured in a compact manner in that on a chip on which the micropumps are attached are arranged, only a small area is used. In addition, there is many years of experience for known micropumps with flap valves, so that the structures of the micropump can be produced with a high degree of accuracy.

However, the use of passive check valves in the micropumps 100a and 100b, which open or close at the respective overpressure or underpressure, has the disadvantage that holding the liquid is not always guaranteed. Even a slight excess pressure at the inlet opening 118 can cause the passive check valves to open slightly, as a result of which a fluid can flow into or out of the pump chamber 116.

When the micropumps 100a and 100b are used in the pipetting device described above, leak rates occur even with small pressure differences in the opening direction due to the insufficient holding of the metering liquids described above. In particular, holding large amounts of liquid is only possible to a limited extent due to the hydrostatic pressure and the associated leakage rates.

A major disadvantage of the micropumps 100a and 100b is that a so-called fluidic short circuit can occur at high pressure pulses. If the micropump 100a is actuated during the aspiration of the metering fluid, a pressure p2 arises in the pipette channel 132 which is lower than a pressure pl of the environment which is in communication with the outlet opening of the micropump 100a. However, since the pipette channel communicates with the outlet opening of the micropump 100b and further the surroundings with the inlet opening of the micropump 100b, the pressure difference causes the valves of the micropump 100b to open due to the pressure difference, so that the micropump 100b causes a fluidic short circuit occurs. Furthermore, when the metering fluid is expelled, a fluidized short circuit occur. In this case, actuation of the micropump 100b generates a pressure p2 in the pipette channel which is greater than the pressure pl of the environment which is in communication with the inlet opening of the micropump 100b. Due to the pressure difference between the environment and the pipette channel, the valves of the micropump 100a can open, so that a fluidic short circuit through the micropump 100a can occur during the metering process.

As is known, the risk of a fluidic short-circuit can be reduced by suitable actuation of the piezoelectric element 126, in which short-term high pressure pulses are avoided. The piezoelectric element 126 can be driven, for example, by means of a sinusoidal signal shape. However, generating the sine shape requires additional circuitry in that additional components and circuit parts have to be provided.

Another disadvantage of the known pipetting device described above is that it is expensive to manufacture. The micropumps 100a and 100b are formed from three wafers which are arranged one above the other after structuring. The arrangement of the wafers requires a high degree of precision so that the structures of the various wafers which are arranged one above the other are positioned exactly at the intended position. The effort increases with each additional wafer.

Furthermore, in the known micropumps 100a and 100b, the middle pump body section 112 must be made thin in order to keep an overall height of the pump chamber 116 low, so that a high compression capacity is achieved. The thinning of the wafer is known to be carried out by grinding or grinding. However, grinding causes mechanical loads that lead to damage. sensitive microstructures or break the wafer.

Alternatively, a thin wafer can also be used as the starting wafer in the manufacture of the middle pump body section. In order to transport and store the thin wafers appropriately during the manufacturing process, however, complex handling devices that are specially adapted to the thin wafers are required. Furthermore, when handling the thin wafers, there is a risk of the wafer breaking, which increases the rejection rate in the case of mass production and increases the production costs.

Another disadvantage that results in the use of passive check valves in the micropumps 100a and 100b is that simple fluid guidance is not possible since the fluid flow is impeded when the flaps flow in and out. In particular, the degree of opening of the flaps depends on the overpressure or underpressure in the pump chamber, so that depending on the pressure present, different courses of the fluid result when the inlet or outflow occurs. This must be taken into account when designing the micropump.

Further, to form the exhaust flap valve 124, an exhaust passage 130 in the pump body portion 110 must have a large diameter due to the elongated shape of the valve flap 124a. As a result, an outer surface of the pump body section 110 is reduced, which makes it difficult to attach the micropump.

In addition, 1, a significant disadvantage of the pipetting device of FIG. That two micro pumps have to be 100a and 100b, in order to achieve a suction and metering, since the micro-pumps 100a and 100b le ^¬ can be operated diglich with a pumping direction. This requires a lot of effort in production and additional space consumption.

A pipetting device which comprises two micropumps with passive flap valves corresponding to the pipetting device described with reference to FIG. 1 is described, for example, in DE 198 47 869 A1.

WO 99/10 099 AI discloses a microdosing system which comprises a micromembrane pump and a free-jet metering device. The micromembrane pump is connected to a reservoir by means of an input and furthermore has an output which is connected to an input of the free-jet metering device by means of a line. Passive check valves are provided at the inlet and outlet of the micro-diaphragm pump, so that a liquid can be pumped from the reservoir to the free jet meter. The free jet dosing device further comprises a pressure chamber with two openings, each of which forms an inlet or outlet of the free jet metering device. The micromembrane pump and the free-jet metering device each further comprise a membrane in order to change a volume of the pressure chamber.

DE 197 06 513 AI shows a microdosing device which has a pressure chamber which is connected via an inlet to a media reservoir and also has an outlet for ejecting fluid. The device comprises a membrane with an actuator in order to change the volume of the pressure chamber. To prevent backflow through the channel connected to the media reservoir, a valve is arranged between the pressure chamber and the media reservoir. The valve can be operated by means of a piezoelectric drive, which actuates a movable membrane for closing. EP 0 725 267 A2 discloses an electrically controllable micro pipette which comprises a micro ejection pump. The micro-ejection pump comprises a chamber with a chamber wall which can be controlled by means of an electrically controllable actuator device. In operation, the pumping chamber of the micro-ejection pump is filled with fluid from a supply and is subsequently discharged via an outlet capillary.

EP 0 568 902 A2 shows a micropump with a pump chamber which has an inlet and an outlet, each of which has a valve to close the same. The pump chamber also has a membrane which can be actuated by means of a micro-actuation device. In operation, the diaphragm is deflected, thereby reducing the pressure in the pumping chamber so that when the inlet valve is lifted from its seat while the outlet valve remains in a closed position, liquid enters the pumping chamber through the inlet and subsequently is expelled through the open outlet valve.

The object of the present invention is to provide a pipetting device and a method for operating a pipetting device which enable safe and stable metering of a metering fluid.

This object is achieved by a pipetting device according to claim 1 and a method for operating a micropump according to claim 12.

The present invention provides a pipetting device with the following features:

a micropump with a pump chamber with a first opening and a second opening;

means for changing the volume of the pump chamber;

a first active valve for opening and closing the first opening

a second active valve for opening and closing the second opening; and

a pipette tip, which is connected to the first or second opening via the pipette channel.

Furthermore, the present invention provides a method for operating a pipetting device with the following steps:

actively closing the first or second opening, thereby separating an environment from the pump chamber;

actively opening the second or first opening, thereby connecting the pump chamber to the pipette channel;

Increasing the volume of the pump chamber for drawing a dosing fluid through the pipette tip; and

Reduce the volume of the pump chamber to expel the dosing fluid through the pipette tip.

The present invention is based on the knowledge that a pipetting device with a micropump with a stable and safe dosing behavior can be realized by using a micropump with passiv Ven valves for opening or closing openings of a pump chamber is removed. According to the present invention, a micropump with active valves for opening and closing the pump chamber openings is used in the pipetting device according to the invention.

As a result, the openings of the pump chamber can be securely closed even when counterpressures occur. This prevents a fluid short circuit at high pressure pulses and prevents leak rates from occurring.

The use of a micropump with active valves according to the invention enables operation in two pump directions, so that only one micropump is required for suction and metering.

Through the provision of active valves, a simple fluid guidance is also achieved since, in contrast to the known micropumps with flap valves, the flow of the inflowing or outflowing fluid is not impeded by the flaps. This also results in simple fluid guidance in inlet and outlet channels which are connected to the openings. Furthermore, the openings can be formed with a simple and symmetrical shape. This simplifies structuring the openings during the manufacture of the micropump.

In addition, a manufacturing process is kept simple in the pipetting device according to the invention, since critical production of thin flexible flaps is not necessary.

In contrast to the known pipetting device with a micropump with passive flap valves, it is not necessary in the pipetting device according to the invention to arrange an elongated valve flap in a large dimensioned outlet channel of a pump body. This allows an outer surface of the pump body to have a large attachment have surface for attaching the micropump to a support, so that a simple and secure attachment of the micropump is possible.

A preferred embodiment of the present invention comprises a pipetting device with a micropump, in which the active valves comprise piezoelectric valves. Furthermore, the device for changing the volume of the pump chamber preferably has a pump membrane which can be operated with a piezoelectric actuating device for changing the volume. The piezoelectric actuating device preferably comprises a thin piezo-active layer which is applied to an outer side of the pump membrane.

The pump diaphragm is preferably arranged between holding elements which allow the diaphragm to bend without having to accept adverse effects on the active valves.

The micropump is preferably formed with a layer structure from two structured flat disks which are arranged one above the other. This makes the manufacture of the micropump simple and inexpensive. A semiconductor material, and particularly preferably a silicon material, is preferably used as the material of the disks.

Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

1 shows a cross-sectional illustration of a known pipetting device which has two micropumps with passive flap valves;

Fig. 2 is a schematic cross-sectional view of an embodiment of a micropump, the at a pipetting device according to the present invention is used; and

3 shows a schematic cross-sectional illustration of an exemplary embodiment of a pipetting device with a micropump according to the present invention.

A micropump 200 used in an embodiment of the present invention is explained below with reference to FIG. 2.

2, the micropump 200 has a pump body 210, which is preferably formed from a disk-shaped first pump body section 212 and a disk-shaped second pump body section 214. The pump body sections 212 and 214 are arranged one above the other in the vertical direction (y-axis) and connected to one another at edge regions thereof via connecting structures. The pump body sections 212 and 214 preferably comprise disks made of a semiconductor material and particularly preferably made of silicon. In other exemplary embodiments, however, the pump body 210 can have any other microstructurable material. The disk-shaped pump body sections 212 and 214 are preferably structured using known lithography and etching techniques and connected using known connection techniques to form the pump body 210.

An elongated pump chamber 216 is formed in the micropump 200 by a recess 218 in the lower pump body section 212 and a trough-shaped recess 220 in the upper pump body section 214. The recesses 218 and 220 pointing in the direction of the pump body are preferably arranged centrally in the horizontal direction (x-axis) in order to achieve a symmetrical structure. The pump chamber is preferably of a small size Height formed to achieve a high compression ratio.

The micropump 200 also has two openings 222 and 224 for introducing or discharging a fluid into the pump chamber 216, each of which is formed on opposite sides of the pump chamber 216 in the lower pump body section 212. The openings 222 and 224 each extend in the shape of a truncated cone from a surface facing outward with respect to the pump body 210 to an inwardly facing surface of the lower pump body section 212. However, the openings can also have other shapes, such as a cylindrical shape be educated. The openings 222 and 224 preferably have a symmetrical shape in order to simplify their manufacture.

A first active valve 226 for closing and opening the opening 222 is arranged above the opening 222. The first active valve 226 includes a closure member 228 formed on an inner surface of the second pump body portion 214 with respect to the pump body 210. The closure element 228 is formed in such a way that, when the first active valve 226 is open, it is spaced from the opening 222 in the vertical direction.

The closure element 228 has a flat closure surface which extends in the horizontal direction over valve seat structures 222a and 222b arranged laterally of the opening 222, so that the opening 222 is completely closed by the closure ^element 228 in a closed state of the valve 226 becomes. The valve seat structures 222a and 222b are preferably designed such that when the valve 226 is closed, the contact surface of the closure element 228 is kept small. The small contact surface ensures a secure closure by the closure element 228, since there is a risk of a leaky closure, for example due to unevenness in the Valve seat structures 222a and 222b, is minimized with decreasing contact area.

The closure element 228 is connected laterally by thin webs with holding elements 232 and 234. As a result, the closure element 228 is arranged flexibly with respect to the holding elements 232 and 234 and can be brought from an open state into a closed state, in which the closure element 228 sits on the valve seat structures 222a and 222b with a closure surface and closes the opening 222 ,

In order to bring about the opening and closing of the first active valve, a first piezoelectric actuation element 230 is arranged on a surface of the closure element 228 opposite the closure surface. The first piezoelectric actuator 230 preferably comprises a thin layer of a piezoelectric material, such as quartz.

The first piezoelectric actuating element 230 can be connected via electrical connections (not shown) to a control device (not shown) in order to achieve a contraction or expansion of the first piezoelectric actuating element 230 by applying an electrical voltage, which respectively cause vertical displacements of the closure element 228.

Furthermore, a second active valve 236 is formed above the opening 224, which is preferably designed corresponding to the first valve 226. More precisely, the second active valve 236 has a closure element 238 which is arranged above the opening 224 and which is connected to holding elements 242 and 244 via laterally arranged webs. Likewise, the second active valve 236 comprises a second piezoelectric actuation element 240 for enabling the vertical movement of the closure element 238. Valve seat structures 224a and 224b are formed corresponding to the first valve to the side of the opening 222.

As will be explained in more detail later, the piezoelectric elements 230 and 240 open and close the openings 222 and 224 by applying a corresponding electrical voltage, so that the pump chamber 216 for admitting or discharging a pump medium through the openings 222 and 224 can be closed or opened.

To change the volume of the pump chamber, the pump chamber 216 has a thin membrane 246, which is arranged between the holding elements 234 and 244. As a result, the thin membrane 246 can be flexibly bent between the holding elements 234 and 244, so that the volume of the pump chamber 216 can be changed by actuating the membrane. The solid formed holding members 234 and 244 prevent a movement of the shutter members 228 and 238 is transferred upon an actuation of the diaphragm 246, so that an adverse influence on the active valves by the Be ^¬ movement of the membrane 246, which, for example, to an opening of a closed valve can lead is prevented. Furthermore, the holding elements 234 and 244 also serve as fastening devices which enable the micropump 200 to be fastened to a carrier.

In a pump body 210 side of the diaphragm 246 is further remote from a piezoelectric diaphragm actuator 250 for actuating the membrane 246 is arranged ^¬. The piezoelectric membrane actuating element 250, like the piezoelectric actuating elements 230 and 240, preferably has a thin layer made of a piezoelectric material. Furthermore, the piezoelectric membrane actuating element 250 can be connected to a control device via electrical connections (not shown) in order to enable an electrical voltage to be applied. The pump 200 is a pump based on the peristaltic principle, in which the actuating elements 230, 240 and 250 are actuated in succession in predetermined sequences.

Operation of the micropump 200 according to this principle is explained in more detail below.

A first pumping direction in which a fluid is pumped from the opening 222 to the opening 224 is first explained below.

During a suction process, the second valve 236 is first actuated to close the opening 224. The second valve 236 is actuated by applying an electrical voltage to the second piezoelectric element 240, which causes the closure element 238 to be moved downward in the horizontal direction to close the opening 224. The first piezoelectric element 230 is then actuated to open the opening 222.

Subsequently, a voltage is applied to the piezoelectric diaphragm actuator 250 to cause the diaphragm 246 to deform, so that the volume of the pump chamber 216 increases. This creates a negative pressure in the pump chamber 216, as a result of which a fluid is sucked into the pump chamber 216 from the opening 222. After the suction process has ended, the first valve 226 is closed.

To pump out the fluid stored in the enlarged pump chamber 216, the second valve 236 is then actuated by applying an electrical voltage to the second piezoelectric actuator 240 to open the opening 224. After opening, a voltage is applied to the piezoelectric diaphragm actuator 250 which causes the volume of the pump chamber 216 to decrease. This causes the fluid to flow out of the Pump chamber 216 out and pushed through the opening 224.

The opening 222 is preferably connected to a first fluid reservoir when the micropump 200 is operating, while the opening 224 is connected to a second fluid reservoir. This causes fluid to be pumped from the first fluid reservoir into the second fluid reservoir in the pumping operation described above. The first and second fluid reservoirs can be, for example, ambient air or a container with liquid or gas.

After performing the pumping cycle described above, the pumping process can be repeated one or more times to pump a desired amount of fluid from the first reservoir to the second reservoir.

In order to pump the micropump 200 with a second pumping direction, in which a fluid is pumped from the opening 224 to the opening 222, the active valves 226 and 236 are operated in a correspondingly reversed manner based on the explanations above.

More specifically, in the second pumping direction, the first valve 226 is first closed in a suction process, the second valve 236 is opened and then the membrane is actuated to increase the pump chamber volume. As a result, a fluid is drawn into the pump chamber 216 from the opening 224. The second valve 236 then closes the opening 224, while the first valve 226 opens the opening 222. The membrane 246 is subsequently actuated to reduce the pump chamber volume, as a result of which the fluid in the pump chamber 216 is expelled through the opening 222.

An exemplary embodiment of a pipetting device 252 is explained below with reference to FIG which uses the micropump 200 explained with reference to FIG. 2 for dosing the dosing medium.

3, in the pipetting device 252 the micropump 200 is arranged on a carrier element 254, a pipette channel 256 formed in the carrier element 254 being connected to the opening 224 of the micropump.

The pipetting device 252 also has a pipette tip 258 which has an opening at the front end for sucking in and expelling a dosing liquid. At a rear end, the pipette tip 258 has a connecting element 260, which is designed to connect the pipette channel 256 to the interior of the pipette tip 258. The connecting element 260 is preferably inserted into the pipette channel 256 in a detachable manner in order to enable the pipette tip 258 to be exchanged.

The carrier element 254 further comprises a channel 262 which is connected at a first end thereof to the opening 222 of the micropump 200. A second end of the channel 262, which is arranged laterally on the carrier element, is in contact with an environment which, for example, has air.

As shown in FIG. 3, the pipetting device 252 can have a filter 264 between the second end of the channel 262 and the surroundings connected to the channel, which filter is connected to the channel 262 via a connecting element 266a.

The environment typically includes air as a medium, so that the filter is preferably designed as an air filter. The filter 264 can comprise all known filter types, such as, for example, particle filters, chemically selectively absorbing filters or electrostatic filters. Filtering the air prevents contamination of the dosing medium by particles or chemical contamination of the air. It also prevents contamination from accumulating on the active valves, which can prevent the openings from being sealed. The filter 264 can also have an outer connection element 266b in order to enable a connection to a suction line arranged outside the carrier element 252.

An operation of the pipetting device 252 will now be explained in more detail below.

To suck in a dosing medium, which preferably comprises a liquid, the micropump 200 is first operated with a pumping direction in which a working medium, which is for example air or another gaseous medium, is sucked out of the pipette channel 256 into the pump chamber 216 via the opening 224 and pumped through the opening 222 into an environment connected to the channel 262. This pump direction corresponds to the second pump direction explained with reference to FIG. 2, so that a representation of the assigned work processes of the micropump can be found in the corresponding explanations above.

Causes the pumping operation for sucking in that a negative pressure is created in the interior of the pipette tip 258 is drawn whereby the Do ^¬ siermittel in the interior of the pipette tip 258th The pumping process for sucking in the dosing agent 268 can be repeated until the desired amount of the dosing agent 268 is sucked into the pipette tip 258. During the intake which ges as a gasförmi ^¬ pad 270 is increasingly displaced in the pipette tip 258 working medium contained by the dosing 268th The gaseous cushion 270 ensures that the pipette channel does not come into contact with the dosing medium. This prevents the dosing agent from being changed when the pipette tip 258 is exchanged for dosing another dosing agent is contaminated by dosing agent residues of the previous dosing agent present in the channel.

After the desired amount of dosing agent has been sucked in, the valve is actuated to close in order to hold the dosing agent in the pipette tip 258.

In a subsequent metering process, the micropump 200 is operated with the reverse pumping direction, in which the working medium of the micropump 200 is sucked in from the environment via the opening 222 and is pumped into the pipette channel 256 via the opening 224.

This pumping direction corresponds to the first pumping direction explained with reference to FIG. 2, so that reference is made to the corresponding explanations for a precise description of the pumping processes.

The pumping of the working medium from the environment into the pipette channel 256 generated in the pipette channel 256 and in the gaseous cushion 270 an overpressure, so that the dosing means 264 pettenspitze by the expanding air cushion from the Pi ^¬ is urged or pushed 258th The Pumpvor ^¬ can be repeated gang until a desired Do- siermittelmenge from the pipette tip 258 applied WUR ^¬ de.

As has already been mentioned above, the active valves 226 and 236 achieve a tight closing independent of a back pressure that occurs. This has an advantageous effect on the pipetting device 252, since a fluidic short circuit, as can occur in known micropumps with flap valves, is prevented. The pipetting device 252 therefore achieves high metering accuracy. Unintended detachment of the dosing medium while holding it in the pipette tip is also achieved due to the low leakage rates of the active valves.

Although in the described exemplary embodiments the active valves of the micropump 200 are designed as piezoelectric valves, other exemplary embodiments of the present invention can include other actively actuable valve types, such as, for example, mechanically actuable valves, electrostatic valves or electromagnetic valves.

To actuate the membrane, instead of the piezoelectric actuating device described, any other known actuating device for actuating the membrane, such as an electrostatic actuating device, can be used.

Furthermore, any known device can be used in other embodiments, which allows changing the pump chamber volume. Such devices can include, for example, rotatable elements for compressing and decompressing a fluid in the pump chamber.

Although in the exemplary embodiment described the pump chamber has only two openings, in alternative exemplary embodiments it can also have more than two openings with correspondingly assigned active valves. This enables selective pumping, in which, for example, different fluids can be pumped alternately from different reservoirs into the pump chamber and can then be pumped into predetermined other reservoirs via selectively selected openings. In this exemplary embodiment, a selective mixing of different fluids can be carried out in the pump chamber, a mixing ratio being adjustable by controlling the active valves. The use of the pump chamber thereby achieved as a “mixing ^reactor Λλ ^furthermore shows the partly on that a good mixing is achieved by the high pressures in the pump chamber.

Furthermore, the pipetting device with a micropump according to the present invention is not restricted to the exemplary embodiment of an air cushion pipetting device shown. Other exemplary embodiments can include, for example, a pipetting device based on the direct displacement principle or a microtiter pipetting device, in each of which the micropump according to the invention is used for dosing the dosing agent.

Claims

claims

1. Pipetting device with the following features:

a micropump (200) with

a pump chamber (216) having a first opening (222) and a second opening (224);

a device (246, 250) for changing the

Volume of the pump chamber (216);

a first active valve (226) for opening and closing the first opening (222);

a second active valve (236) for opening and closing the second opening (224); and

a pipette tip (258) which is connected to the first (222) or second (224) opening via the pipette channel (256).

2. Pipetting device according to claim 1, wherein the active valves of the micropump (200) comprise piezoelectric valves (226, 236).

3. pipetting device according to claim 1 or 2, wherein the means for changing the volume of the pump chamber comprises a membrane (246) and a piezoelectric actuator (250) for actuating the membrane.

4. Pipetting device according to claim 3, in which the membrane (246) is arranged between holding elements (234, 244).

5. pipetting device according to one of claims 1 to 4, further comprising a pump body (210), the one comprises a first disk-shaped body element (212) and a second disk-shaped body element (214) arranged above it.

6. pipetting device according to one of claims 1 to 5, wherein a pump body (210) comprises a semiconductor material.

7. pipetting device according to one of claims 1 to 6, wherein the pump chamber (216) further comprises at least one further opening; and where

the micropump (200) further has at least one further active valve for opening and closing the at least one further opening.

8. pipetting device (252) according to one of claims 1 to 7, further comprising a filter (264) for filtering a working medium of the micropump (200).

9. pipetting device (252) according to one of claims 1 to 8, wherein the pipetting device (252) is an air cushion pipetting device.

10. pipetting device according to one of claims 1 to 8, wherein the pipetting device is a direct displacement pipetting device.

11. Pipetting device according to one of claims 1 to 8, wherein the pipetting device is a microtiter

Pipetting device is.

12. A method for operating a pipetting device according to one of claims 1 to 11 with the following steps: actively closing the first or second opening (222), thereby separating an environment from the pump chamber (216);

actively opening the second or first opening (224), thereby connecting the pump chamber (216) to the pipette channel (256);

Increasing the volume of the pump chamber (216) for drawing in a dosing fluid through the pipette tip (258); and

Reduce the volume of the pump chamber (216) to expel the dosing fluid through the pipette tip