An air displacement pipettor

Abstract

An air displacement pipettor including a base plate and a back plate with a size equal to or smaller than the base plate. A rim section of the back plate is adhered the top surface of the base plate leaving a central portion the back plate adjacent to, and non-adhered to the top surface of the base plate. A piezoresistive disk is sealably attached to the top surface of the back plate and configured to contract or expand upon applying a voltage to the piezoresistive disk thereby deforming the central portion of the back plate and / or the base plate for creating a chamber between the base plate and the back plate. An outlet for connecting the chamber to an adapter which is configured for releasably connecting the pipettor to a pipetting tip such that volume changes of the chamber may be used for aspirating or dispensing of liquids.

Description

[0001] 1 TC 0868 An air displacement pipetor

[0002] FIELD OF THE INVENTION

[0003] The current invention relates to an air displacement pipettor driven by a piezoresistive element and to a laboratory automation apparatus comprising the air displacement pipettor.

[0004] BACKGROUND OF THE INVENTION

[0005] The automation of workflows in diagnostic or clinical laboratories is of key importance as the number of samples to be tested has significantly increased such that certain operations require laboratory automation apparatuses for tasks that used to be executed manually by a laboratory' assistant. Those laboratory' automation apparatuses may include: i) robotic arms for moving or handling labware components on a working table of the laboratory automation apparatus; ii) automated liquid handling devices for aspirating and / or dispensing liquids in the labware; iii) sample processing equipment such as stirrers, heaters, coolers, thermocyclers, DNA library' preparation equipment, and iv) analytical or chemical testing equipment such as for example microplate readers, DNA sequencers including microfluidic chips, Liquid Chromatography devices (HPLC) and the like. A work surface of the laboratory automation apparatus provides limited space for positioning all the equipment and devices or storing the labware products.

[0006] The automated liquid handling devices mentioned above (ii) require the accurate and repetitive manipulation (e.g, aspirating, dispensing and mixing) of small volumes in the microliter range and include automatic pipettes including pipettors for controlled dispensing of the liquids. The pipettors include pipetting heads or pipetting channels with connectors for attaching pipetting tips to the pipettors. The automated liquid handling device may include a plurality (for example two, four, six or eight) pipetting channels coupled to a robotic arm for moving the pipetting channels, and therewith the pipetting tips, to different positions on the work surface of the laboratory automation apparatus for collecting different liquids such as sample liquids or processing liquids. Processing liquids may include reagents, buffer solutions, solvents, staining solutions and the like. The robotic arm may also include a spreading device for adjusting the distance between the pipetting channels. It is preferred that the pipetting channels are arranged in a compact and space saving arrangement as small sample volumes need to be aspirated and / or dispensed in. for example plates with densely packed wells arranged in, for example a 96-weII-pIate format. Smail pipettors or pipettors that can be arranged tn a space saving configuration may be beneficial for such a laboratory' automation apparatus.

[0007] The pipettor may include a syringe pump as disclosed in CH702974A1. A motor-driven syringe pump moves a piston of a syringe in a cylinder. A three-way rotary' valve is operatively connected to the syringe and can be switched from a first position where the syringe is in fluid connection with the liquid that flows into the syringe when the piston is partially withdrawn into the cylinder. The valve is then switched into a second position, in which the syringe is in fluid connection with a pipeting tip for dispensing the sample or reagent by advancing the piston in the cylinder. 2 TC 0868 An example of an Air Displacement Pipettor (ADP) is disclosed in US7976749B2. A piston is motor driven for linear movement in a cylinder thereby changing the total volume of a chamber defined by the cylinder and pipetting tip connected to the cylinder. An under pressure may be created by retracting the piston which is used for aspirating liquids when the distal end of the pipe tting tip is in contact with a liquid surface, and an over pressure may be created by advancing the piston in the cylinder thereby dispensing the aspirated liquid through the pipetting tip.

[0008] An example of an Air Restriction Pipettor (ARP) is disclosed in EP2569642A1. One or more pipetting heads are fluidically connected to a vacuum source or to a pressure source. The pipetting heads are separated from the vacuum respectively from the pressure source by two-way valves. The pipetting device is operated by opening and closing the 2-way valves between the vacuum reservoir and the pipeting tip respectively between the pipetting tip and the pressure source. Based on the timing for the opening or closing of the valves, a specific amount of liquid is aspirated into, or dispensed from the pipetting tip.

[0009] Another example for an ADP is disclosed in GB2510027A. The air displacement pipettor includes a pair of piezo membranes and both provide the walls of a pumping chamber. Actuating the pair of piezo membranes results in contraction or expansion of the pair of membranes whereby an excess pressure or a vacuum is produced in the pumping chamber.

[0010] EP3597298B1 discloses a droplet forming device comprising a liquid holder, a film having a discharge hole and two or more piezo based vibration generators surrounding the discharge hole for vibrating the film and dispensing droplets from the discharge hole.

[0011] DESCRIPTION OF THE INVENTION

[0012] There is a need for a compact pipettor for use in a laboratory automation apparatus. There is a need for a simple and accurate air displacement pipetor requiring less components or parts.

[0013] It is an objective of the present invention to overcome the disadvantages of the prior art and provide a simple and compact air displacement pipettor. Those objectives are solved by the independent claims using a piezoresistive element, further exemplary embodiments are evident from tire dependent claims and the following description including the Figures.

[0014] A first aspect relates to an air displacement pipettor comprising a base plate with a top surface and a bottom surface and a back plate w ith a top surface and bottom surface. The size of the back plate may be equal to or smaller than the base plate. Alternatively, the size of the base plate may be equal to or smaller than the back plate. A rim section of the back plate is sealably attached or sealably adhered to the top surface of the base plate thereby leaving a central portion of tire bottom surface of the back plate adjacent to, and non-adhered to the top surface of the base plate. A central portion on the top surface of the base plate is preferably not adhered to the bottom surface of the back plate. A piezoresistive disk, element or membrane is attached to the back plate, preferably to the top surface of the back plate. The piezoresistive disk or element is configured to contract or expand upon applying a voltage to, or across the piezoresistive disk thereby deforming the central portion of the back plate and / or the base plate and creating a cham ber between the top surface of the base plate and the botom surface of the back plate. The pipettor includes an outlet TC 0868 for connecting the chamber to an adapter, and the adapter is configured for releasably connecting a pipetting tip to the pipettor such that volume changes of the chamber may be used for aspirating or dispensing of liquids from the pipettor,

[0015] Tire base plate and / or the back plate may be essentially Hat. The base plate and the back plate are preferably oriented parallel to another when the piezo resistive disk or element is not activated. The top surface of the base plate and the bottom surface of the back plate may be essentially flat in the central portion when no voltage is applied. Alternatively, one or both the base plate and the back plate is curved or one or both the top surface of the base plate and the bottom surface of the back plate is curved. The top surface of the base plate and / or the bottom surface of the back plate may include indentions, pockets or grooves in the central portion. There may be multiple grooves in the back plate or the base plate and the grooves may be circular or semicircular and oriented around a common center.

[0016] The base plate and the back plate may be equally elastically deformable and the chamber tnay be bordered by two curved walls when applying the voltage. The back plate may be more deformable compared to the base plate. A relatively flexible back plate may be adhered to a relatively rigid base plate such that the chamber is bordered by a flat top stirface on the base plate and a curved bottom surface on the back plate upon applying a voltage to the piezoresistive element. One of the base plate and back plate may be provided as a bistable element, such as a bi stable disk or clicker.

[0017] The base plate and / or back plate are manufactured from elastic materials and are elastically deformable such that the volume of the chamber may be increased upon activating the piezo resistive element and may elastically contract with a volume reduction of the chamber when no voltage is applied. The retraction force may be provided by the elasticity of the back plate and / or the base plate. Alternatively, the size of the chamber increases when no voltage is applied or when a voltage is switched off or when the polarity of the voltage is reversed The base plate and or the back plate may be prestressed providing the chamber between the two plates and the size is reduced upon applying the voltage to the piezo resistive element

[0018] The rim section preferably has a width that is less than 20% of the maximum lateral dimension of the back plate. The rim section of the back plate includes the rim surrounding the back plate. The rim section includes a rim section on the bottom surface of the back plate. The rim may be attached to the base plate and / or the botom surface of the rim section may be adhered to the base plate.

[0019] The piezoresistive disk, element or membrane may be shaped as a flat disk, as a block or as a cylinder and a botom surface of the disk, a side wall of the block or the end-face of the cylinder may be coupled, attached or adhered to the top surface of the back plate. The block or cylinder may be coupled to a rigid wall for transferring the displacement of the piezo element to the back plate. The piezoresistive element may deform upon applying a voltage across the element or vice versa a voltage is generated upon deforming the piezo element, for example upon deforming the chamber of the pipettor.

[0020] The outlet is configured for connecting the chamber to the adapter, or the central portions of top surface of the base plate and bottom surface of the back plate that are not adhered to another to the adapter. The outlet may be incorporated in the top surface of the base plate and / or the bottom surface of the back 4 TC 0868 plate. The adapter may be sleeve shaped having a proximal section for connecting to the pipettor and a disial section for connecting to the pipetting tip. The proximal section may be coupled to, or couplable to one or both the base plate or the back plate. The proximal section may be sandwiched between the base plate and the back plate. The proximal section may include a threaded section for a screw type connection to the pipettor The proximal section may be adhesively coupled to the pipettor or coupled in a press-fit engagement. The pipettor may include the adapter in that the adapter is integrated in the base plate and / or the back plate. The distal section may include an outer wail surface adapted for a releasable press fit engagement with a pipetting tip, preferably with a disposable pipetting tip. The outer wall may include a cone shaped section or at least one circumferential rim radially extending outwards from the axis of the sleeve for engaging an inner surface of a bore at the proximal end of the pipeting tip.

[0021] The air displacement pipettor according to the present disclosure comprises a compact design comprising two essentially flat plates oriented parallel to another. This may lead to a credit card shaped pipettor. The compact and flat design allows for a compact arrangement of a plurality' of pipettors in a parallel arrangement. The air displacement pipettor according to the present disclosure comprises less parts, for example only one piezo disk may be used thereby providing a simple and cost-efficient solution for the air displacement pipettor.

[0022] A skirt ou the top surface of the back plate extends beyond and surrounds the piezo resistive disk and an electrode may be attached to the top surface of the piezo resistive disk and a counter electrode to the top surface of skirt for applying the voltage to. or across the piezo resistive disk. The piezo resistive disk contracts in a direction parallel to the plane of the back plate upon applying the voltage Alternatively, the expansion / contraction is in a direction perpendicular to the back plate. The deformation of the element or disk results in a deformation of the back plate adhered to the disk and / or a deformation of the base plate that is adhered to the back p late via the rim section. The skirt on the top surface is located between the external edge of the piezo resistive disk and the rim of the back plate. The back plate may be made from an at least partially' electrically conductive material or is coated with an electrically conductive coating.

[0023] In an embodiment, a plurality of electrodes may be attached to different locations on the top surface of the piezo resistive disk or element thereby locally activating and deforming the piezoresistive disk. Each of the plurality of elements may be connected to a control unit of the pipettor or to a control unit of a laboratory automation apparatus including the pipettor. The control unit may locally address a voltage io the piezo resistive disk for locally deforming tire disk such that the local deformation of the back plate and / or base plate may be controlled. The volume and / or shape of the chamber used for the air displacement pipettor may be controlled accordingly.

[0024] The electrodes at different locations may be differently poled or powered with different voltage levels. The control unit may address the electrodes in an alternating manner to expand or contract different areas of the piezo resistive element.

[0025] In another embodiment, the air displacement pipetor may include a piezoresistive disk iticluding a plurality of separated piezoresistive elements and each piezo resistive element is connected to a 5 TC 0868 separate electrode for locally activating and deforming the back plate. The control unit may locally activate one or more of the piezo resistive elements thereby locally deforming the back plate for increasing and / or decreasing the internal volume of the chamber The local activation of the one or more piezo resistive elements may be used to change the shape and volume of the chamber of the air displacement pipettor. The space on the top surface of the back plate between two adjacent piezo resistive elements cannot be activated Tach of the plurality of separated piezoresistivc elements may be individually activated with a voltage, or no voltage is applied or the polarity of the voltage is rever sed.

[0026] The plurality of separated piezoresistivc elements may be linear, circular, semi-circular, quadratic, or rectangular shaped. The plurality of piezoresisiive elements may be concentrically arranged with respect to each other on the top surface of the back plate. The plurality of piezoresistivc elements may be arranged as a sunburst for, for example the linear elements.

[0027] In an embodiment, the bottom surface of the back plate of the rim section is attached to the top surface of the base plate using an adhesive. Adhesives may be chosen to be relatively rigid, or relatively flexible. In the case of flexible adhesives, they may be chosen to have a high flexure life. The adhesive may be a heat cured adhesive such as an epoxy adhesive or an LTV cured adhesive such as an acr late- based adhesive Adhesives might be silicone, urethane or other cured adhesives. In another example, the rim section is welded to the top surface of the base plate. The welding may be executed using laser welding or ultrasonic welding The rim section may be soldered to the base plate. The attachment is done in a controlled maimer in that only the rim section is attached and not the central portions.

[0028] The base plate and back plate may be each made from a metal or a metal alloy. The base plate and back plate may be made from a metal sheet. The base plate and the back plate may be each made from identical or different metals or metal alloys. Metals and metal alloys may be selected from steel, brass, copper or aluminum). One of the base plate or back plate may be made from a non-metal such as a polymer or ceramic One of the base plate or back plate may be made from a composite material such as a fiber reinforced polymer. For a ceramic or polymer material a conductive coating may be applied io the surface or to one of the top surface or bottom surface. The base plate and the back plate may be coated with a noble metal such as gold, silver or platinum. The base plate and or the back plate may be made of a printed circuit board (PCB) material with integrated conductive layers and integrated cavities or passages for connecting the pipette lip volume to the chamber volume.

[0029] In another embodiment, a manifold connects the outlet to a plurality of air displacement pipettors thus providing a total chamber volume available for pipetting that is composed of a plurality of sub volumes of each pipettor coupled to the manifold.

[0030] In another embodiment, a modulated voltage is applied to the piezoresistivc disk thereby vibrating the backplate and / or the base plate wherein the resulting acoustic wave in the outlet is used for liquid level detection. The modulated voltage may be combined with, or applied on top of the voltage used for contraction or expansion of the piezoresisiive disk or element. The vibration of the disk generates the acoustic wave that propels towards the outlet and via the adapter into the pipetting tip. In addition to being used as a pumping element, the piezo disk or membrane may thus be used as acoustic 6 TC 0868 transmitter, and possibly even as an acoustic receiver or sensor by using a separate electrode area on the piezo membrane. This may enable a means for pressure liquid level detection by vibrating the disk while moving down the pipetting tip towards the liquid surface The resulting acoustic wave in the air passage to the pipeting tip is detected using either a separate pressure sensor or using the piezo membrane as the acoustic receiver. The acoustic impedance within the pipeting tip will change when the end of the tip touches the liquid and closes the opening for the acoustic waves. The control unit may be configured to detect the liquid level from the acoustic impedance measurements.

[0031] The piezoresistive disk or membrane may be used as a sensor or acoustic receiver or a separate pressure sensor is used and configured for detecting the change in acoustic impedance when the end of a pipette tip touches the liquid to be aspirated.

[0032] The deformation of the back plate and / or the deformation of the base plate may be measured to determine the volume of the chamber.

[0033] In an embodiment, measuring electrodes are attached each to the back plate and tire base plate providing a capacitive sensor for measuring the gap or distance between the electrodes for quantifying the deformation of the back plate and / or base plate that define the size of the pumping chamber. One of the electrodes may be attached to the top surface of the piezo resistive disk, alternatively, one of the electrodes is attached to the top surface of the back plate between the back plate and the piezo resistive disk, as yet another alternative the electrode is located on the bottom surface of the back plate. The other one of the electrodes may be attached to the top surface or bottom surface of the base plate. The capacitive sensor is coupled to the control unit or a separate sensor control unit and a capacitive sensor voltage may be applied across the two electrodes. The response signal is received by the sensor unit and depends on. for example the distance between the two electrodes. The data received from the capacitive sensor may be used by the control unit for controlling the volume of the chamber and therewith the aspirated or the dispensed liquid volume. As an example, a modulated voltage signal is applied to one or both of the electrodes for detecting the charge time of the capacitor in the response signal.

[0034] In another embodiment, strain gauges are attached to the back plate and or base plate for quantif ing the degree of deformation of the plates and therewith the size of the chamber The strain gauges may be attached io the bottom surface of the back plate, to the top surface if the back plate between the top surface and the piezo element, or the stain gauge may be attached to the top surface of the piezo element

[0035] In an embodiment, a groove is provided forming a channel in the bottom surface of the back plate and / or the top surface of the base plate, The channel provides the outlet for connecting the chamber to the adapter. The channel may cross the sealed connection between the bottom surface of the back plate and the top surface of the base plate. The groove may be a linear or curved groove. Constriction elements may be included in the groove for regulating the air flow.

[0036] A second aspect relates to a laboratory automation apparatus comprising the air displacement pipettor The laboratory automation apparatus may include a robotic arm with a plurality of air displacement pipettors and the back plates of each air displacement pipettor of the plurality of air 7 TC 0868 displacement pipettors may be organized in a parallel or stacked arrangement. This may lead to a space saving arrangement by stacking the multiple Hat, for example credit card shaped ADPs.

[0037] The invention will now be described using the drawings It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects and / or embodiments of the invention.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the present invention are described in more detail with reference to the attached drawings presentin:

[0040] Figure 1: Cross sectional view of an air displacement pipettor including a piezoresistive element that is not actuated.

[0041] Figure 2: Cross sectional view of the air displacement pipettor of Figure 1, a piezoresistive element that is actuated providing the pumping chamber,

[0042] Figure 3: Side view of the air displacement pipettor of Figure 1,

[0043] Figure 4: Side view of the air displacement pipettor according to another embodiment: Multiple electrodes on the piezoresistive element,

[0044] Figure 5: Side view of the air displacement pipettor according to another embodiment: Multiple piezoresistive elements on a back plate,

[0045] Figure 6: Side view of the ah' displacement pipettor according to another embodiment: Multiple piezo air displacement pipettors coupled by a manifold,

[0046] Figure 7: Sectiononal view of tire air displacement pipettor according to another embodiment:

[0047] Detection of the air displacement volume using a capacitive sensor.

[0048] Figure 8: Further example for an air displacement pipettor with the piezoresistive element deforming in a direction perpendicular to the base plate.

[0049] Figure 9: Further example for an air displacement pipettor with the piezoresistive element deforming in a direction perpendicular to the base plate.

[0050] Figure 10: A laboratory automation apparatus including two air displacement pipettors.

[0051] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0052] Definitions: The distal end or distal direction is defined by the flow direction for tire liquid, thus the distal end of a pipetting tip is defined by the outlet when dispensing liquid and the proximal end is opposite to the distal end. The indefinite article "a" or "an" does not exclude a plurality’. For example, "a base plate” 8 TC 0868 does not exclude the fact that there may be two base plates that functionally or structurally fulfill the purpose of “a base plate”. In the claims, the word "comprising" does not exclude other elements or steps. The piezoresi stive material deforms when a voltage is applied to the material or, vice versa, a voltage is generated upon deformation. The piezoresistive materials can be broadly classified as either ciystalline, ceramic, or polymeric. The most commonly produced piezoelectric ceramics are lead zirconate titanate (PZT), barium titanate, and lead titanate.

[0053] Figure 1 discloses an air displacement pipettor 1 including a flat base plate 2 with a top surface 4 and a bottom surface 5 oriented essentially parallel to another. A back plate 3 is positioned onto the base plate 2. The back plate 3 is essentially flat with a top surface 6 and a bottom surface 7 oriented parallel to another. The top surface 4 of the base plate 2 is adjacent to the bottom surface 7 of the back plate 3 when no voltage is applied to the pipettor as depicted in Figure 1. The back plate 3 has a total surface area smaller compared to the surface area of the base plate 2. A rim section 8 and / or rim 29 of the back plate 3 is attached to the top surface 4 of the base plate 2. The rim section 8 is adhered along a continuous path, for example a full circle in the embodiment presented in Figures 1 to 3. The rim section 8 or the rim 29 of the back plate is atached to the top surface of the base plate and a central portion 9a, 9b of the back plate 3 and base plate 2 is not attached to another. The rim section 8 may be welded to the base plate 2 or attached using an adhesive or welding seam 19 (Figure 2). The rim section 8 could also be attached by mechanical means such as an o-ring and clamping arrangement against the base plate 2. It may be preferable for the join of the rim 8 to the base plate to be compliant, while ensuring no leakage or air. A piezo resistive element, disk or sheet 10 is attached to the top surface 6 of the back plate 3 and the surface area of the disk 10 is smaller than the surface area of the back plate 3 thereby leaving a skirt 14 on the back plate 3 surrounding the piezoresistive disk 10. The piezoresistive disk 10 may expand in a plane parallel to the top surface of the base plate 2 upon applying a voltage to the disk thereby locally deforming the back plate 3 and providing a chamber or pumping chamber 27 (Figure 2). The stiffness of the base plate 2 exceeds the stiffness of the back plate 3 in the example presented in Figures 1 to 3 such that the contraction or expansion of the piezoresistive disk deforms the back plate 3 only. Alternatively, the base plate 2 may deform upon activation of the piezo resistive disk 10. The central portion 9a on the bottom surface 7 of the back plate 3 deflects and departs from the top surface of the base plate 2, The back plate is preferably made from an electrically conductive material such as a metal sheet, a brass sheet, an aluminum sheet, or a copper sheet. The sheets are relatively thin, below 2 mm thickness, preferably below 1 mm thickness, more preferably below 0.5 mm thickness. Alternatively, the backplate 3 is made from an electrically insulating material such as a sheet of a polymeric material or composite material that is at least partially coated with an electrically conductive coating. The base plate 2 is preferably made from an electrically conductive material such as a metal plate. The thickness of the plate preferably exceeds the thickness of the back plate in the example presented in Figures 1 to 3.

[0054] In an alternative embodiment, the situation for the activated and non -activated state in Figures 1 and 2 is reversed in that the piezo element is activated in Figure 1 and not activated in Figure 2. The piezoelectric, element 10 can, for example, be attached to the top surface 6 of back plate 3 by means of a thermally curable epoxy. Plates 3 and 10 can be constrained to a flat state while the epoxy is being cured at an elevated 9 TC 0868 temperature. Upon cooling and when the constraint is removed, the differential thermal expansion differences between the PZT material and the metal of the back plate will result in a shape as shown in Figure 2. When voltage is applied to cause the PZT material to contract, the disk will flatten to the shape shown in Figure 1.

[0055] A side view for the air displacement pipetor 1 is presented in Figure 3, The back plate 3 and the piezoresistive disk 10 have a circular shape. Other shapes of the disk and plate can be envisaged as long as the central portions do not adhere to another, for example rectangular or elliptical shaped piezo disks or back plates. The base plate 2 may have any shape as long as the back plate 2 can be fully covered by the base plate. An electrode 15 is attached to the piezo resistive disk 10 and a cormter electrode 16 is attached to the skirt 14 of the top surface of the back plate 3 such that a voltage may be applied to the piezoresistive disk 10 using a control unit 30. The control unit 30 includes a power source and may apply a continuous voltage to the disk 10. The power source may also generate a modulated voltage to tire disk 10 such that the disk may be set in a vibrating mode for generating acoustic waves. An outlet 1 1 is connected or connectable to the chamber 27, or to the central portions 9a.9b via a channel 25. The channel 25 is provided in this embodiment as a groove in the top surface 4 of the base plate 2. An adapter 12 is coupled to the channel 25 and the adapter provides a mechanical interface to a pipetting tip 13. Volume changes of the pumping chamber 27 may be used for aspiration and / or dispensing of liquids via the pipetting tip 13.

[0056] Another example for an air displacement pipettor I and controlling the deformation of the back plate 3 and therewith the size and shape of the chamber 27 is presented in Figure 4. A plurality of electrodes 15 is attached to different locations on the top surface of the piezoresistive disk 10. All electrodes 15 and the counter electrode 16 are coupled to the control unit 30 which may direct different voltage signals to different locations of the piezoresistive disk 10, alike commutating of an stepper motor. The voltage applied to different sections may be equally poled or partially counter poled thereby locally deforming the piezo disk and thereby controlling the deformation of the back plate 3.

[0057] Another example for an air displacement pipettor I and controlling the deformation of the back plate 3 is presented in Figure 5. The piezo resistive disk 10 is provided as a plurality of piezoresistive rings 18 which are concentrically arranged with respect to each other and attached to the top surface 6 of the back plate 3. Each ring 18 is separated from an adjacent ring and each ring is connected to a separate electrode 15. Each electrode 15 is coupled to the control unit 30 for locally applying a voltage to the rings 18 and thereby locally controlling the deformation of the piezo resistive rings and therewith also controlling the deformation of the back plate 3 and the size and shape of the pumping chamber 27. No voltage, a voltage or a reverse poled voltage may be applied to each piezo resistive ring 18. The ring-shaped top surface 32 of the back plate between two adjacent piezo rings 18 cannot be actively deformed.

[0058] Another example for an air displacement pipettor with an augmented pumping volume is depicted in Figure 6. The outlet 11 is coupled to a plurality of air displacement pipettors 1 via a manifold 20. The back plate 3 of each pipettor may be attached to a common base plate 2 and the size of the back plates may be different for each pipettor 1. The pumping chambers for each pipettor are coupled to the outlet 11 via the 10 TC 0868 manifold 20. The control unit may individually address an activation voltage to each pipettor for controlling the total pumping volume.

[0059] An example for detecting the size and shaped of the pumping chamber 27 for the air displacement pipettor is presented in Figure 7. An electrode 21 is attached to the bottom surface of the base plate 2 and another electrode 22 is attached to the top surface of the piezoresistive disk 10. The electrode attached to the piezoresistive disk may be the same electrode as used for applying the source voltage for deforming the piezo resistive disk. The electrodes 21, 22 are coupled to a sensor unit providing a capacitive sensor 23. The capacitive sensor 23 may be integrated into the control unit 30. The capacitive response of the sensor 23 depends on the size, shape and composition of the dielectric medium between the electrodes 21,22. Most notably, the distance between the electrodes 2.1,22 changes when the piezoresistive disk 10 is activated and the change in impedance is used for detection the size and shape of the chamber 27.

[0060] A further example for the air displacement pipettor 1 is presented in Figures 8 and 9. The main difference to the pipettor presented in Figures 1 and 2 is that the deformation of the piezo element in the direction perpendicular to the base plate is used for deforming the back plate and / or the base plate. The piezo resistive element 10 is provided as a disk, cylinder or block with one face attached to a solid body or frame 33 and the opposite face being attached to the top surface 6 of the back plate 3. Applying a voltage to the piezo resistive cylinder expands or contracts the piezoelement in the direction indicated by the arrow for creating the chamber 27 between the top surface of the base plate and the bottom surface of the back plate. The frame or solid body may be directly or indirectly mechanically coupled to the base plate 2. As an example, the base plate and the frame 33 are directly connected to each other via a U-shaped element or a fork.

[0061] A laboratory automation apparatus 26 including two of the above-mentioned air displacement pipettors 1 is presented in Figure 10. The laboratory automation apparatus includes a work surface 31 defining an x-y plane and a robotic arm 28 positioned above the work surface 31, The work surface 31 provides space for labware components such as well plates, containers, or sample holders. The work surface is also a vailable for processing equipment such as shakers, heaters or thermocyclers. The work surface may include analytical testing devices such as plate readers or microfluidic chips used for DN A sequencing. The robotic arm in this example includes two piezo pipettors 1, alternatively, the robotic arm holds four' or eight pipetors 1. The robotic arm 28 may include a spreading device for adjusting the distance between the outlets of each pipettor 1. The piezo pipettors 1 are flat due to the arrangement of the back plate 3 and the base plate 2 such that a plurality of pipettors may be arranged in a parallel and space saving configuration. Preferably the distance between two adjacent pipetors amounts to 9 mm or 4.5 mm corresponding to the pitch of the 96 well plate respectively the 384 well plate (SLAS Format). The robotic arm may control and move each pipettor to different locations on the work surface of the laboratory' automation apparatus. Each pipettor may include a pipetting tip used for aspirating liquid from a sample container by first contacting the liquid, followed by increasing the volume of the chamber 27. The liquid may be partially dispensed in a well plate positioned on a different location on the work surface by moving the pipettor to the location of 11 TC 0868 the well plate, lowering the pipettor and finally reducing the volume of the pumping chamber 27. The laboratory automation apparatus includes a control unit 30 that controls the movement of the robotic arm and the size and shape of the pumping chamber of each pipettor 1. TC 0868

[0062] LIST OF REFERENCE SIGNS

[0063] 1 Air displacement pipettor

[0064] 2 Base plate

[0065] 3 Back plate

[0066] 4 Top surface base plate

[0067] 5 Bottom surface base plate

[0068] 6 Top surface back plate

[0069] 7 Bottom surface back plate

[0070] 8 Rim section

[0071] 9a Central portion, section backplate

[0072] 9b Central portion, section base plate

[0073] 10 Piezoresistive element, sheet, disk

[0074] 11 Outlet

[0075] 12 Adapter

[0076] 13 Pipetting tip

[0077] 14 Skirt

[0078] 15 Electrode

[0079] 16 Counter electrode

[0080] 17 Electrode

[0081] 18 Piezo resistive element, ring

[0082] 19 Adhesive, welding seam

[0083] 20 Manifold

[0084] 21 Electrode

[0085] 22 Electrode

[0086] 23 Capacitive sensor

[0087] 24 Gap

[0088] 25 Channel

[0089] 26 Laboratory automation apparatus

[0090] 27 Chamber

[0091] 28 Robotic arm

[0092] 29 Rim

[0093] 30 Control unit

[0094] 31 Work surface

[0095] 32 Ring shaped top surface between piezo elements

[0096] 33 Frame

Claims

13 TC 0868 CLAIMS1. An air displacement pipettor (1) comprising:a base plate (2) with a top surface (4) and a bottom surface (5),a back plate (3) with a top surface (6) and bottom surface (7).a rim section (8) of the back plate (3) being sealably attached to the top surface (4) of the base plate (2). leaving a central portion (9a) of the bottom surface (7) of the back plate (3) adjacent to. and non-adhered to the top surface (4) of the base plate (2),characterized bya piezoresistive disk (10) attached to the top surface (6) of the back plate (3), the piezoresistive disk being configured to contract or expand upon applying a voltage across the piezoresistive disk (10) thereby deforming the central portion (9a.9b) of the back plate (3) and / or the base plate (2) for creating a chamber (27) between the top surface (4) of the base plate (2) and the bottom surface (7) of the back plate (3).an outlet (11) for connecting the chamber (27) to an adapter (12) configured for releasably connecting the pipettor (1) to a pipetting tip (13) such that volume changes of the chamber may be used for aspirating or dispensing of liquids.

2. The air displacement pipetor (1) according to claim 1, wherein a skirt (14) on the top surface (6) of the back plate (3) extends beyond and surrounds the piezo resisti ve disk (10) and wherein an electrode (15) is attached to the top surface of the piezo resistive disk (14) and a counter electrode (16) to the top surface (6) of skirt (14) for applying the voltage across the piezo resistive disk for contraction or expansion of the disk in a direction parallel to the plane of the back plate.

3. The air displacement pipetor (1) according to claim 2, wherein a plurality of electrodes (15.17) is attached to different locations on the top surface of the piezo resistive disk for locally activating and deforming the piezoresistive disk (10)4. The air displacement pipettor (1) according to claim 2, wherein the piezoresistive disk (10) comprises a plurality of separated piezoresistive elements (10.18) and whereby each piezo resistive element ( 10, 18) is connected to a separate electrode (15.17) for locally activating and deforming the central portion (9a.9b) of the back plate (3) and / or the base plate (2).14 TC 08685. The air displacement pipettor (1) according to claim 4, wherein the plurality of separated piezoresistive elements (10,18) is concentrically arranged with respect to each other.

6. The air displacement pipettor (1) according to any of the previous, wherein the bottom surface (7) of the back plate (3) of the rim section (8) is attached to die top surface (4) of the base plate (2) using an adhesive (19).

7. The air displacement pipetor (1) according to any of the previous claims, wherein the base plate (2) and the back plate (3) are each made from different metals.

8. The air displacement pipetor (1) according to any of the previous claims, wherein a modulated voltage is applied to the piezoresistive disk for vibrating the backplate and wherein the resulting acoustic wave in the outlet is used for liquid level detection.

9. The air displacement pipetor (1 ) according to claim 8. wherein the piezoresistive disk is used as a sensor or wherein a separate pressure sensor is used and configured for detecting the change in acoustic impedance when the end of a pipette tip touches the liquid to be aspirated.

10. The air displacement pipettor according to any of the previous claims wherein the deformation of the back plate (3) and / or the base plate (2) is measured to determine the volume of the chamber (27).

11. The air displacement pipetor (1) according to claim 10. wherein measuring electrodes (21,22) are attached each to the back plate (3) and the base plate (2) providing a capacitive sensor (23) for measuring the gap (24) between the electrodes (21.22) for quantifying the deformation of the back plate (3) and / or base plate (2) defining the size of the chamber (27).

12. The air displacement pipettor (1) according to claim 10 wherein a strain gauge is attached to the back plate (3) and / or base plate (2) for quantifying the deformation of the back plate (3) and / or base plate (2) defining the size of the chamber (27)15 TC 0868 13. The air displacement pipettor (1) according to any of the previous claims, wherein a channel (25) is provided in the bottom surface (7) of the back plate (3) and / or the top surface (4) of the base plate (2) providing the outlet (11) for connecting the chamber (27) to the adapter (12).

14. A laboratory automation apparatus (26) comprising the air displacement pipetor (I) according to any of the previous claims.

15. The laboratory automation apparatus (26) according to claim 14 wherein a robotic arm (28) of the laboratory automation apparatus (26) comprises a plurality of air displacement pipettors (1) according to claims 1 to 12 and wherein the back plate (3) of each air displacement pipettor (1) of the plurality of air displacement pipettors is organized in a parallel or stacked arrangement.

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