Patent Description:
When large quantities of samples have to be examined in medical, chemical, analytical or pharmaceutical laboratories, automated laboratory systems are usually used today to enable rapid and reliable processing of each individual sample. Such laboratory systems are often designed as liquid processing systems for handling liquid volumes. Such liquid processing systems, e.g. air displacement pipetting devices or system liquid pipetting devices, comprise in particular pipettors both for aspirating and dispensing liquids or dispensers exclusively for dispensing liquids. Most laboratory applications require very precise pipetting operations to achieve satisfactory analytical accuracy. In order to guarantee such precise pipetting, the volume ranges in which the automated laboratory systems operate are limited. With common automated laboratory systems, it is not possible to precisely aspirate and precisely dispense liquid volumes that differ by more than a factor <NUM> or maximum <NUM>. Consequently, there are automated laboratory systems on the market for larger volumes (e.g. "mL range", such as <NUM> to <NUM>) and automated laboratory systems for smaller volumes (e.g. "µL range", such as <NUM>µL to <NUM>µL). Furthermore, automated laboratory systems may be limited to a minimum volume or maximum volume that can still be aspirated and dispensed by design. In case a laboratory handles the analysis of samples that require pipetting operations of different liquid volumes, the laboratory is in the need of at least either two different automated laboratory systems operating in different volume ranges or one automated laboratory system comprising various pipettors or pipetting arms.

<CIT> discloses an air displacement pipette including a segmented, stepped piston configured to displace additional air at a higher velocity during a blowout stroke, thereby enabling improved dispensing accuracy by more completely dislodging adhering liquid from a pipette tip following the preceding dispensing stroke.

The objective of the present invention is to make any major adaption to an automated laboratory system superfluous by nonetheless allowing for operating the automated laboratory system in different volume ranges.

This object is achieved by the displacement device according to claim <NUM>, which allows for operating an automated laboratory system designed for a specific volume range in a volume range different from said specific volume range.

A displacement device according to the invention comprises a first fluid space and a second fluid space. The first fluid space is separated into a first chamber and a second chamber by a first piston displacement area of a first piston. The first piston is arranged in a movable manner within the first fluid space. The first chamber of the first fluid space is connectable to a pipetting device. The first piston is actuatable by an actuation volume of the working fluid of the pipetting device. The second fluid space is separated into a first chamber and a second chamber by a second piston displacement area of a second piston. The second piston is arranged in a movable manner within the second fluid space. The second piston is constructed to displace a displacement volume of a fluid located within the second chamber of the second fluid space when the second piston is actuated. The second piston is actuated in dependence on the first piston being actuated by the actuation volume. The actuation volume is different from the displacement volume. The first fluid space and the second fluid space are removably connected.

The working fluid of the pipetting device can be a gas (such as air, nitrogen,. ), a liquid (such as water, oil,. ) or a combination thereof. Subsequently, three different types of pipetting devices are explained in more detail to illustrate the operating mode of the displacement device according to the invention in combination with said pipetting devices. Please note that the subsequent illustration is not a conclusive enumeration.

The pipetting device can e.g. be an air pipetting device operating based on the principal of a classical piston-operated pipette that comprises an air cushion between the piston and the liquid to be aspirated or dispensed, the air cushion representing the working fluid. When connected to a displacement device according to the invention, it is the air of the air cushion that gets displaced by the piston of the air pipetting device and in consequence of said displacement actuates the first piston of the displacement device.

The pipetting device can also be a fluid pipetting device. Such a fluid pipetting device can be based on the principal described in e.g. <CIT> by means of a motor-driven syringe pump moving a piston of a syringe in a cylinder. A valve, such as a three-way-valve, is operatively connected to the syringe and can be switched by e.g. rotating the three-way-valve. In a first position of the valve, the syringe is in fluid connection with e.g. a system liquid, a system gas or a reagent that flows into the cylinder when the piston is partially withdrawn from the cylinder, the system liquid or system gas representing the working fluid. The valve is then switched into a second position, in which the syringe is in fluid connection with a dispenser tip for dispensing the reagent or a displacement device according to the invention. In case the piston is now moved further into the cylinder, the working fluid or reagent is pressed out of the syringe and led to the dispenser tip or the displacement device according to the invention. Either the reagent gets dispensed or the working fluid actuates the first piston of the displacement device according to the invention. The first piston in the illustrated example is consequently driven by a liquid or a gas (generally summarized by the term fluid) but can also be driven by a combination thereof. In case the syringe comprises some air or any other gas, or a liquid that does not mix with the system liquid before the piston is partially withdrawn from the cylinder in the first position of the valve, this air or gas, or liquid is also led to the displacement device according to the invention and forms an air or gas cushion, or liquid cushion between the first piston of the displacement device and the system liquid. In such cases, the working fluid comprises not only the system liquid or system gas but also the substance forming the cushion. Instead of a syringe pump, it is also possible to control the flow of the working fluid by e.g. a peristaltic pump or a membrane pump.

The pipetting device can also be a pipetting device with a vacuum reservoir and a pressure reservoir as e.g. described in <CIT>. One or more pipetting channels are fluidically connected to both a vacuum source and a pressure source. The individuals pipetting channels are separated from the vacuum source and the pressure source by <NUM>-way valves, respectively. The working fluid of such a pipetting device is e.g. system gas or system gas combined with system liquid. The vacuum of the vacuum reservoir is e.g. provided by a vacuum pump. The vacuum of the vacuum reservoir is assumed to be constant. The pressure reservoir is e.g. provided by a pressure pump. The pressure of the pressure reservoir is assumed to be constant. The pipetting device is operated by opening and closing the <NUM>-way valve between the vacuum reservoir and the pipetting channel and between the pipetting channel and the pressure reservoir. Based on the time between opening and closing the valve and vice versa ("valving time"), a specific amount of working fluid or lack of working fluid is provided to the pipetting channel. Such a pipetting device is called in this application a valve-controlled pipetting (VCP) device. It is therefore not a piston that moves an air cushion as in a classical piston-operated pipette but overpressure and underpressure that actuate the first piston of the displacement device according to the invention when connected to a VCP pipetting device. Nonetheless, overpressure can e.g. be represented by an amount of pressurized air such that the first piston is again actuated by a working fluid as in the previous examples.

In general, a pipetting device can be understood as any means that provides for aspirating and dispensing a specific volume of a fluid in a controlled manner. It is then this specific volume that provides for the working fluid of the pipetting device, which working fluid acts as or in other words represents or forms the actuation volume for actuating the first piston. The guiding of working fluid of the pipetting device into or the removing of working fluid of the pipetting device from the first chamber of the first fluid space provokes indirectly via the first piston a movement of the second piston and thus the aspiration or dispensation of the displacement volume. By actuating the first piston via the actuation volume, the first piston is driven either pneumatically or hydraulically depending on the working fluid being a gas or a liquid. The working fluid can also be a combination thereof such that the first piston can be actuated pneumatically and hydraulically at the same time. Although the working fluid of the pipetting device itself may be driven mechanically (e.g. by a rigid displacer such as a plunger operated manually or automatically), the first piston is directly and immediately actuated pneumatically and/or hydraulically and not by mechanical coupling, i.e. by a user interface such as a handle or a grip (e.g. an activator grip such as a thumb press) being coupled in a fix or removable manner to the first piston. In other words, the first piston is not coupled (neither in a fix nor removable manner) to a physical (e.g. rigid) means for actuating it. One can say that the force for actuating the first piston is applied contactless, i.e. it is not a solid-state body that is transmitting the force for actuating the first piston. The first piston and preferably also the first chamber of the first fluid space are thus constructed such that the first piston can be actuated pneumatically and/or hydraulically.

Concerning the general design of the first fluid space and the second fluid space, various basic shapes are possible, such as cylindric or cuboid. To avoid any hindering of the pistons' movement, an unvarying cross-sectional shape along the movement path of the pistons is beneficial. Sections of the fluid spaces that do not belong to the movement paths can comprise varying cross-section shapes, such as conical.

The first and second pistons can have various shapes and can be designed as massive or hollow bodies. For instance, a piston can be a continuous body, such as a cylinder, or a body with recesses. The piston displacement area describes the largest cross-sectional area of the pistons body perpendicular to the movement path of the piston. In case of the piston being a continuous body, there is only one cross-sectional area and thus the surface of the piston providing for the smallest second chamber and the largest first chamber is considered the piston displacement area. When the second chamber is located underneath the first chamber, it is the lower surface of the piston that is considered the piston displacement area. This definition holds for both the first and the second piston. In case a piston comprises several sections with an identical maximum cross-sectional area perpendicular to the movement path, it is the cross-sectional area of the first section viewed from the first chamber to the second chamber that represents the piston displacement area.

To be connectable to a pipetting device, in particular to the pipetting tube of such a device, wherein the pipetting tube describes the coupling means of the pipetting device such as the cone for plugging on disposable tips, the first chamber of the first fluid space can comprise a connection means. This connection means can provide e.g. for friction fit or form fit. The connection is preferably established in a gas-tight and/or liquid-tight manner. The first chamber of the first fluid space can for instance comprise on the side facing away from the first piston an opening with an opening section designed in analogy to the opening section of commercial disposable tips that are intended to be stuck to the pipetting tube of a pipetting device. Such a design allows sticking the displacement device to the pipetting tube similar to the sticking of a disposable tip to the pipetting tube, the opening section representing the connection means. The opening section of the first chamber of the first fluid space is for instance a hollow cylinder either with or without a slight conical shape and an opening section diameter of <NUM> to <NUM>, in particular of <NUM> to <NUM>. To achieve a friction fit, it is also an option to design the opening section of the first chamber of the first fluid space in an elastic manner e.g. by using an elastic material such as rubber or a polymer to build the opening section, the elastic material representing the connection means. It is also possible to provide a profiled structure on the inner surface of the opening section by means of material risings (e.g. by implementing an o-ring or two or more bulges), material recesses and/or structure bars, the profiled structure representing the connection means. To provide for a form fit, the first chamber of the first fluid space can for instance comprise protrusions designed complementary to recesses of the pipetting tube or vice versa, the protrusions or recesses representing the connection means. Alternatively, the connection can also be provided by magnetic forces or any other known way of connecting two items. The connection between the displacement device and the pipetting device is preferably detachable.

The displacement device works the most reliable when the pistons can be moved with as little friction as possible and when the pistons provide for a fluid-sealing separation of the first chamber and the second chamber. The first condition allows for a smoother movement of the pistons and thus for a better controllable movement. The second condition ensures that the desired volume (i.e. the displacement volume and/or the first volume addressed later on) is displaced by the piston's movement by a predetermined distance. In case some fluid could pass from the first chamber to the second chamber and was not displaced reliable by the piston's movement, it would be hard to predict what the actual volume of the displaced fluid is. It is in particular beneficial when the pistons are in direct contact against the inner wall of the fluid spaces. Both conditions can be influenced by the choice of material for both the pistons and the fluid spaces, in particular for the outer surface of the piston and the inner surface of the fluid spaces, i.e. for the contact area of the pistons and the fluid spaces. Low friction materials such as PTFE may be used. For the first piston not being in contact with the fluid of the second chamber of the second fluid space, i.e. the fluid of interest, it is also an option to use lubricants, such as silicon lubricants having a friction decreasing and a sealing effect. Such lubricants can be provided by adding a small volume of them to the first chamber of the first fluid space. To further improve the reliability of the displacement device, it can be beneficial to use a liquid as working fluid to minimize the compressible amount.

The displacement volume that gets displaced by the second piston is for instance a sample to be analyzed or a reagent or chemical in general. This so-called substance of interest can be a liquid (i.e. liquid of interest) such as e.g. water, puffer, acid and so on or a gas (being summarized together with liquids as fluid of interest).

However, the displacement volume is not limited to fluids and can also include solid materials e.g. in powder form or suspensions. Since the displacement device of the invention will probably predominantly be used to aspirate and dispense fluids, most examples and illustrations address the fluid of interest. This is not to be understood as a limitation of the invention to fluid displacement volumes. The actuation of the first piston is controlled by the volume of the working fluid of the pipetting device, namely the actuation volume. If now the second piston is actuated in dependence on the first piston and thereby displaces a volume that is different from the actuation volume, the actual displacement volume of the fluid of interest is different from the actuation volume predetermined by the pipetting device. In consequence, the displacement device provides for a volume transmission having a transmission ratio given by the ratio of the actuation volume to the displacement volume. The displacement device allows thus for the displacement and also for the aspiration and dispensation of a volume of a fluid of interest different from the volume predetermine by the working fluid of a pipetting device controlling the displacement and also aspiration and dispensation process. Since the volume difference can be of several magnitudes, the displacement device makes purchasing a plurality of pipetting devices of different operation volume ranges or the purchase of a single pipetting device with several pipetting arms, each arm operating in a different volume range, superfluous.

Please note that the displacement device according to the invention does also allow for operating a hand pipette designed for a specific volume range in a volume range different from said specific volume range. The invention and all its aspects are thus not limited to a use in combination with automated laboratory systems. However, the benefit of the invention and all its aspects is larger for automated laboratory systems since they are more expensive and take up far more space than hand pipettes.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the first piston constructed to displace a first volume of a fluid located within the second chamber of the first fluid space. The first volume is in particular of the same size than the actuation volume.

According to this embodiment, the first piston is constructed to displace a first volume of a fluid located within the second chamber of the first fluid space when the first piston is actuated by an actuation volume of the working fluid of the pipetting device. The first volume that gets displaced by the first piston is for instance ambient air or any kind of system fluid and is not consumed during the analytical procedure.

Since the actuation of the first piston is controlled by the actuation volume, the first volume that gets displaced by the first piston is also controlled by the actuation volume, preferably such that the size of the first volume is equivalent to the size of the actuation volume. Such an equality is given when none of the fluid (e.g. air or liquid) of the actuation volume can pass the barrier provided by the first piston. In this case, the displacement device provides for a volume transmission having a transmission ratio given by the ratio of the first volume to the displaced volume, the transmission ratio being identical to the transmission ratio given by the ratio of the actuation volume to the displacement volume.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the second piston a positive displacement piston.

Implementing the second piston as a positive displacement piston is in particular beneficial for the reliable displacement of small volumes, e.g. for displacement volumes in the range of <NUM> nL to <NUM> nL. In case the second piston is a positive displacement piston, the first fluid chamber of the second fluid space contains a part or even the whole second piston and is thus not an empty space only filled with ambient air or alike as it is the case for other embodiments.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the actuation of the second piston in dependence on the first piston based on at least mechanical coupling and/or magnetic force and/or pneumatic force and/or hydraulic force.

To control the movement of the second piston, several physical principals may be implemented, either alone or in combination. One principal is based on mechanical coupling between the first and the second piston. This is a simple as well as effective and non-costly principle. Another principle is based on attractive forces and/or repulsive forces, in particular based on magnetic forces. However, it is also possible to pneumatically and/or hydraulically couple the first and the second piston in order to determine the movement of the second piston dependent on the movement of the first piston. In one example, the actuation of the second piston in dependence on the first piston is not based on mechanical coupling, e.g. a rigid or solid connection between the first and the second piston.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the first piston either removably mechanically connected to the second piston.

The displacement device can be designed such that it can be disassembled, and single components can be exchanged. Here a removable mechanical connection between the first and the second piston is beneficial. For instance, the second piston, in particular a second positive displacement piston, can be exchanged together with the second fluid space after each displacement operation to avoid cross contamination.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, the second chamber of the first fluid space can be connected to the first chamber of the second fluid space.

A non-permanent and thus detachable connection of the first fluid space to the second fluid space allows for an exchange of the single components and also for the provision of a displacement device set comprising e.g. of a first fluid space adapted to the possible actuation volumes of the pipetting devices it is meant to be used with and a number of at least two second fluid spaces providing for the displacement of different actual displacement volumes.

In case of a non-permanent connection, it is even possible that the pipetting device, in particular the pipetting tube, provides the first fluid space and that the first fluid space is permanently attached thereto. It is also possible that the first fluid space is designed as semi disposable and gets e.g. exchanged after a certain number of uses (e.g. <NUM>) or after each full pipetting run. The fluid path, being a consequence of the fluid connection between the first fluid space and the second fluid space when connected, could be controlled by means of a valve, the valve defining in terms of a mechanical intersection the transition from the first fluid space to the second fluid space (e.g. second fluid space being a positive displacement tip).

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the second fluid space at least in parts formed by a standard positive displacement tip.

This embodiment allows on the one hand for integrating standard positive displacement in the manufacturing process of the displacement device by e.g. using them as prefabricated second fluid spaces. On the other hand, it is e.g. possible to use the first fluid space various times an replace the second fluid space, namely the standard positive displacement tip, after each pipetting operation to avoid contamination.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, controls the first piston the movement of the second piston such that the second piston cannot enter the second chamber of the first fluid space.

In case the first fluid space is meant to be used during several pipetting operations, this embodiment prevents any contact of the fluid of interest and the first fluid space and thus any potential contamination. It is only the second fluid space that gets in contact with the fluid of interest and may therefore need cleaning or replacement between single pipetting operations.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, comprises the second chamber of the first fluid space and/or the first chamber of the second fluid space a pressure equilibrium means.

The pressure equilibrium means may be designed as one or more openings (e.g. through-holes), one or more pressure control valves, one or more elastic sections (e.g. comparable to a balloon or alike) and so on. In one example, the pressure equilibrium means is not designed as (solely or exclusively) one or more openings. In another example, the pressure equilibrium means is not designed as one or more fluid ports. The pressure equilibrium means makes sure that when the first fluid space and the second fluid space, in particular the second chamber of the first fluid space and the first chamber of the second fluid space, are connected in a sealing, i.e. fluid-tight, manner that the movement of the second piston is still dependent on the movement of the first piston and not on the volume of the fluid that gets displaced by the first piston during its movement, namely the first volume.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the actuation volume larger than the displacement volume. The actuation volume is in particular between <NUM> to <NUM> times, further in particular between <NUM> to <NUM> times, larger than the displacement volume.

When the actuation volume is larger than the displacement volume, it is possible to aspirate and dispense a volume of a fluid of interest that is smaller than the actuation volume and thus smaller than the volumes the pipetting device providing the actuation volume is constructed for.

It is for instance possible to aspirate and dispense a volume of a fluid of interest of <NUM> nL with a pipetting device that is designed for aspirating and dispensing volumes of <NUM>µL when using a displacement device providing for a transmission ratio defined by the ratio of the actuation volume to the displacement volume of <NUM>:<NUM>. It is of course also possible to provide for an actuation volume that is smaller than the displacement volume and thus allowing for aspirating and dispensing volumes of a fluid of interest larger than the volume the pipetting device is designed for. In such cases the transmission ratio is smaller than <NUM>, e.g. <NUM>:<NUM> enabling the aspiration and dispensation of a volume of a fluid of interest of <NUM> with a pipetting device that is designed for aspirating and dispensing volumes of <NUM>.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, covers the first piston a first distance when being actuated by the actuation volume of the working fluid of the pipetting device. The first distance is identical to a second distance that is covered by the second piston when being actuated in dependence on the first piston.

This embodiment can for instance be realized by means of a double piston, i.e. an object of the first piston, the second piston and a rigid connecting element such as a bar or alike. A movement of the first piston by a certain distance forces the second piston to perform a movement of the same certain distance. An advantage of the equidistant movement is an easier determination of the transmission ratio of the displacement device.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the first piston displacement area different in size than the second piston displacement area.

This embodiment although allows for an easier determination of the transmission ratio of the displacement device. When the first distance covered by the first piston and the second distance covered by the second piston is known, the first and second piston displacement areas allow for calculating the volume displaced by the first piston and the second piston, namely the so-called first volume and displacement volume. In most cases a conclusion on the size of the actuation volume can be drawn based on the size of the first volume. If the movement of the first piston and the second piston is synchronous, the transmission ratio corresponds to the ratio of the first piston displacement area to the second piston displacement area.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the first piston displacement area larger than the second piston displacement area. The first piston displacement area is in particular between <NUM> to <NUM> times, further in particular between <NUM> to <NUM> times, larger than the second piston displacement area.

In consequence, assumed that the movement of the first piston and the movement of the second piston are synchronized, the transmission ratio would be larger than <NUM>, in particular between <NUM>:<NUM> and <NUM>:<NUM> and further in particular between <NUM>:<NUM> and <NUM>:<NUM>.

In one embodiment of the displacement device according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, comprises the first fluid space and/or the second fluid space an electrode that is constructed to form a measuring capacitor together with a further electrode. It is for instance the first chamber of the first fluid space and/or the second chamber of the first fluid space and/or the first chamber of the second fluid space and/or the second chamber of the second fluid space that comprises an electrode.

The provision of an electrode constructed to form a measuring capacitor together with a further electrode or at least two electrodes to form a measuring capacitor each together with a further electrode allows each for the determination of the actuation volume and/or the first volume and/or the displacement volume depending on the installation location of the electrode or the several electrodes. In particular the actuation volume and further in particular the displacement volume are of significant interest to monitor the reliability of the pipetting operation. The further electrode may be at least in parts aspirated fluid or e.g. the work bench. In case the further electrode is at least in parts formed by the aspirated fluid, the other electrode should be arranged at the second chamber of the second fluid space. Alternatively, the displacement volume and/or the actuation volume and/or first volume can be determined indirectly by determining the position of the first piston and/or the second piston. For this purpose, the piston(s) is(are) designed at least in parts as movable electrode(s) or movable dielectric(s). Monitoring the position of at least one piston, in particular the first piston, can be beneficial in view of varying frictional forces caused by production tolerances and allow for closed loop control of the piston and thus prevent abrupt piston movements. Furthermore, a fresh pipette tip is often used to handle a new sample. Such pipette tips are therefore designed for one-time use and are usually referred to as "disposable pipette tips" (abbreviated to "DiTis"). Depending on the pipetting operation, different pipette tips are used for pipetting.

It is therefore beneficial that an automated pipetting device is capable of detecting whether a pipette tip is connected to the pipette tube at all and, in particular, whether the correct pipette tip is connected. Further information concerning the capacitive volume determination and the determination of the presence and the kind of pipette tip can be derived from e.g. <CIT> or <CIT>.

A further aspect of the invention addresses the provision of a pipetting system comprising a pipetting device and at least one displacement device according to the invention. The pipetting device is for instance an air pipetting device, a fluid pipetting device, an VCP pipetting device, or a combination thereof. The displacement device is connected to the pipetting device. The displacement device is for instance removably stuck to a pipette tube of the pipetting device.

To avoid any modifications of the pipetting device when using it with a displacement device according to the invention, it is beneficial to arrange the displacement device at the pipetting device similar to a standard pipetting tip, namely by sticking a first section onto a pipetting tube of the pipetting device. Instead of aspirating and dispensing a fluid of interest directly, the pipetting device is driving via the working fluid of the pipetting device the first piston of the first fluid space and therewith the second piston of the second fluid space which is then aspirating and dispensing the fluid of interest such that the fluid of interest is indirectly aspirated and dispensed by the pipetting device.

An even further aspect of the invention addresses the provision of a method for displacing a displacement volume of a fluid. The method comprises moving a first piston that is arranged in a movable manner within a first fluid space. The first fluid space is separated into a first chamber and a second chamber by the first piston. The moving of the first piston is actuated by an actuation volume of the working fluid of a pipetting device. The method comprises further moving a second piston that is arranged in a movable manner within a second fluid space. The second fluid space is separated into a first chamber and a second chamber by the second piston such that a displacement volume of a fluid located within the second chamber of the second fluid space is displaced. The moving of the second piston is actuated in dependence on the moving of the first piston. The moving of the first piston is actuated by the actuation volume and the actuation volume is different from the displacement volume.

This method allows, in a manner comparable to the displacement device, for the displacement of a volume of a fluid of interest that is different from the volume the pipetting device driving the movement of the first piston is designed for. Again, the actuation volume is based on the working fluid of the pipetting device and is responsible for the actuation of the first piston such that the moving of the first piston can be described as a pneumatic and/or hydraulic moving. One can say that actuating the first piston is performed contactless, i.e. the actuation is not performed by a solid-state body transmitting an actuation force to the first piston.

In one embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, is the moving of the first piston that is arranged in a movable manner within the first fluid space performed such that a first volume of a fluid located within the second chamber of the first fluid space is displaced.

In one embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, the method comprises further connecting the first chamber of the first fluid space to an pipetting device, in particular an air pipetting device, a fluid pipetting device, an VCP pipetting device, or a combination thereof. The connecting is performed in particular by means of removable sticking at least a first section of the first chamber to a pipette tube of the pipetting device.

In one embodiment of the method according to the invention, which may be combined with any of the preaddressed embodiments and any of the embodiments still to be addressed unless in contradiction, comprises moving the second piston an actuating of the second piston by mechanical coupling and/or magnetic force and/or pneumatic force and/or hydraulic force.

Another aspect of the invention addresses a displacement device set. The set comprises at least one displacement device according to the invention and at least one further second fluid space. This further second fluid space is designed combinable with the first fluid space of the at least one displacement device. The first fluid space of the at least one displacement device is designed separately from the second fluid space of the at least one displacement device. The at least one further second fluid space is separated into a first chamber and a second chamber by the second piston displacement area (A<NUM>) of a second piston arranged in a movable manner within the further second fluid space. The further second fluid space comprises a second piston displacement area (A<NUM>) that is different in size, e.g. smaller or larger, than the second piston displacement area (A<NUM>) of the second fluid space of said at least one displacement device.

By exchanging the second fluid space of the displacement device with the further second fluid space provided in the set, it is possible to aspirate and dispense different displacement volumes having a different volume transmission when set into relation with the actuation volume.

A further aspect of the invention addresses the use of a pipetting system according to the invention, the use of a method according to the invention and/or the use of a displacement device according to the invention and/or the use of a displacement device set according to the invention for translating a first fluid volume to a second fluid volume. These addressed first fluid volume and second fluid volume are for instance represented by the actuation volume Va and the displacement volume Vd or the first volume V<NUM> and the displacement volume Vd.

An even further aspect of the invention addresses the use of a pipetting system according to the invention, the use of a method according to the invention and/or the use of a displacement device according to the invention and/or the use of a displacement device set according to the invention for displacing a displacement volume Vd by means of a pipetting device being constructed to displace an actuation volume Va, said actuation volume Va having a different volume than said displacement volume Vd.

The invention shall now be further exemplified with the help of figures. The figures schematically show:.

<FIG> shows a displacement device <NUM> according to the invention. The displacement device <NUM> comprises a first fluid space <NUM> and a second fluid space <NUM>. In the illustrated embodiment, the first fluid space <NUM> and the second fluid space <NUM> are designed separately and are thus not in fluid-connection or any other physical connection. The first fluid space <NUM> is separated into a first chamber <NUM> and a second chamber <NUM> by a first piston displacement area A<NUM> of a first piston <NUM>. The second fluid space <NUM> is also separated into a first chamber <NUM> and a second chamber <NUM> by a second piston displacement area A<NUM> of a piston, namely the second piston <NUM>.

The first chamber <NUM> of the first fluid space <NUM> is connectable to a pipetting device <NUM> drawn in dashed lines to indicate that the pipetting device <NUM> is not part of the displacement device <NUM>. The pipetting device <NUM> is, for instance, an air pipetting device or a fluid pipetting device. The second chamber <NUM> of the first fluid space <NUM> can be filled with a fluid such as a system liquid or a system gas, but it can also be filled with ambient air. The second chamber <NUM> of the first fluid space <NUM> may comprise a pressure equilibrium means (not shown here) to avoid any negative impact on the mobility of the first piston <NUM>. For instance, such a pressure equilibrium means can comprise one or more through holes, e.g. realized by means of a large opening of any shape at the bottom of the second chamber <NUM> of the first fluid space <NUM>, or a valve. Alternatively, the second chamber <NUM> of the first fluid space <NUM> can partially be made of an elastic material also allowing for a pressure equilibrium.

To move the first piston <NUM>, working fluid of the pipetting device, such as air of the air pipetting device or fluid (includes liquid, gas or combination thereof) of the fluid pipetting device, is either guided into or removed from the first chamber <NUM> of the first fluid space <NUM>. By removing working fluid of the pipetting device from the first chamber <NUM>, the first piston <NUM> is lifted such that the volume of the second chamber <NUM> is increased and the volume of the first chamber <NUM> is decreased. By guiding working fluid of the pipetting device into the first chamber <NUM>, the first piston is pushed downwards such that the volume of the second chamber <NUM> is decreased and the volume of the first chamber <NUM> is increased.

Since the actuation of the second piston <NUM> depends on the first piston <NUM>, and therefore also on the movement of the first piston <NUM>, the guiding of working fluid of the pipetting device into or the removing of working fluid of the pipetting device from the first chamber <NUM> of the first fluid space <NUM> provokes indirectly via the first piston <NUM> a movement of the second piston <NUM>. A lift of the second piston <NUM> leads to a decrease of the first chamber <NUM> of the second fluid space <NUM> and an increase of the second chamber <NUM> of the second fluid space <NUM>. When the second chamber <NUM> of the second fluid space <NUM> is in fluid-connection to a fluid of interest <NUM> (e.g. an analytical sample or any liquid consumable) while the second piston <NUM> is lifted, a volume of the fluid of interest <NUM> is aspirated. When the second chamber <NUM> of the second fluid space <NUM> comprises some fluid of interest <NUM> while the second piston <NUM> is pushed down, a volume of the fluid of interest <NUM> is dispensed, i.e. displaced. <FIG> illustrates the displacement of the fluid of interest <NUM>.

In the shown embodiment, the first piston <NUM> and second piston <NUM> are magnetically coupled such that a downward movement of the first piston <NUM> provokes an identical downward movement, i.e. a simultaneous movement covering the same distance, of the second piston <NUM>.

Since the first piston <NUM> comprises a first piston displacement area A<NUM> (largest cross-sectional area and in this embodiment also only cross-sectional area since it is an unvarying cross-sectional area; schematically illustrated by a double arrow above the corresponding piston) that is smaller than the second piston displacement area A<NUM> of the second piston <NUM> (cross sectional area also indicated schematically by a double arrow), a smaller volume is displaced when the first piston <NUM> is moved downwards by a certain distance compared to when the second piston <NUM> is moved by the same certain distance in the same direction. The displacement device <NUM> does therefore provide for a transformation of fluid volumes. In the shown embodiment, the first piston displacement area A<NUM> of the first piston <NUM> is <NUM> times smaller than the second piston displacement area A<NUM> of the second piston <NUM>. This means that when the pipetting device <NUM> is set to displace a volume of e.g. <NUM> and in consequence moves the first piston <NUM> by e.g. <NUM>, the second piston <NUM> displaces a volume of <NUM> when being moved by <NUM>. The resulting transformation ratio is thus <NUM>:<NUM> and a pipetting device <NUM> that is designed to aspirate and dispense sample volumes of between <NUM> to <NUM> is capable by means of the displacement device <NUM> of this embodiment to aspirate and dispense volumes of <NUM> to <NUM> without the need of any adjustment of the pipetting device <NUM> at all.

<FIG> shows an embodiment of a displacement device <NUM> according to the invention. Its general set-up is comparable to the set-up of the displacement device shown in <FIG>. However, the first fluid space <NUM> of the displacement device <NUM> illustrated here is partially surrounded by the second fluid space <NUM>, although there is no fluid-connection between the first fluid space <NUM> and the second fluid space <NUM>. A physical connection between the first fluid space <NUM> and the second fluid space <NUM> can exist but is not necessary. To indicate that the section surrounded by the second fluid space <NUM> is normally not visible, the first fluid space <NUM> and the first piston <NUM> are drawn in dashed lines. The first piston <NUM> separating the first chamber <NUM> of the first fluid space <NUM> from the second chamber <NUM> of the first fluid space <NUM> and the second piston <NUM> separating the first chamber <NUM> of the second fluid space <NUM> from the second chamber <NUM> of the second fluid space <NUM> are in alignment representing a simultaneous movement of the two pistons <NUM>, <NUM> and thus one way of moving the second piston <NUM> in dependence on moving the first piston <NUM>, the first piston <NUM> being actuatable by the pipetting device <NUM>. <FIG> shows a top view of a cross section along section A-A of the displacement device <NUM> of <FIG> in order to demonstrate how the first fluid space <NUM> is surrounded or enclosed by the second fluid space <NUM>. It is of course also possible to choose a design of a displacement device where the second fluid space is partially or completely surrounded or enclose by the first fluid space. The first fluid space <NUM> and the second fluid space <NUM> of the shown embodiment of the displacement device <NUM> comprise both a rectangular cross section.

<FIG> shows a further embodiment of a displacement device <NUM> according to the invention, the displacement device <NUM> having aspirated some fluid of interest <NUM>. The displacement device <NUM> comprises a first fluid space <NUM> being in fluid-connection with a second fluid space <NUM>. The first fluid space <NUM> is divided into two chambers by a first piston displacement area A<NUM> of a first piston <NUM>, the second fluid space <NUM> is divided into two chambers by a second piston displacement area A<NUM> of a second piston <NUM>. The first piston <NUM> and the second piston <NUM> are mechanically coupled such that an actuation of the first piston <NUM> by a fluid (e.g. gas, such as air, and/or liquid, such as water) provided by a pipetting device <NUM> provokes an actuation of the second piston <NUM>. The first fluid space <NUM> comprises a pressure equilibrium means <NUM> that is arranged on the one hand such that a fluid getting displaced by a downwards movement of the first piston <NUM> does not influence the actuation of the second piston <NUM> and on the other hand such that an upwards movement of the first piston <NUM> is not blocked by the creation of underpressure. Furthermore, the first fluid space <NUM> comprises means for limiting the movement of the first piston <NUM> (and thus for limiting the movement of the second piston <NUM> due to their mechanical coupling) in form of a protrusion located in the first chamber of the first fluid space <NUM>. The protrusion prevents a further uplifting of the first piston <NUM> that would cause the second piston <NUM> to leave the second fluid space <NUM> and enter the first fluid space <NUM>. Such a means for limiting the movement could e.g. also be arranged at the threshold of the first fluid space <NUM> to the second fluid space <NUM> and thus directly hindering the movement of the second piston <NUM>. It is also possible to implement means for limiting the movement of the first piston <NUM> in both the first chamber and the second chamber of the first fluid space <NUM> in order to e.g. define a maximum first volume and thus being able to transfer friction-independent always the same maximum volume. <FIG> illustrates that the displacement device <NUM> of this embodiment is designed for displacing a displacement volume Vd that is smaller than the actuation volume Va provided by the pipetting device <NUM>.

<FIG> shows an even further embodiment of a displacement device <NUM> according to the invention. The double piston <NUM> of the displacement device <NUM> with the first piston displacement area A<NUM> of its first piston <NUM> and the second piston displacement area A<NUM> of its second piston <NUM> is shown in <FIG>. The cross-sectional areas belonging to the displacement areas are schematically illustrated by double arrows. The first piston displacement area A<NUM> represents the largest cross-sectional area of the first piston <NUM>, wherein the second piston displacement area A<NUM> represents the lower surface of the second piston <NUM> since it comprises a constant cross-sectional area. The displacement device <NUM> comprises a first fluid space <NUM> and a second fluid space <NUM> being connected to each other, both fluid-connected and physically connected. The first fluid space <NUM> has a cross-sectional area being larger than the cross-sectional area of the second fluid space <NUM>. The cross-sectional area of the first fluid space <NUM> and the cross-sectional area of the second fluid space <NUM> are essentially identical to the first piston displacement area A<NUM> of the first piston <NUM> and the second piston displacement area A<NUM> of the second piston <NUM> respectively. The rigid connection bar connecting the first piston <NUM> to the second piston <NUM> make sure that a movement by a certain distance in one direction of the first piston <NUM> provokes a predetermined movement of the second piston <NUM> by the same certain distance in the same direction. In other words, the second piston <NUM> is mechanically actuated by the first piston <NUM>. The first piston <NUM> on the other hand is actuated by a fluid provided by a pipetting device (not shown here). The displacement device <NUM> is configured such that it is connectable in a fluid-tight manner to a standard pipetting device well known in the art. For this purpose, the displacement device <NUM> comprises connection means <NUM>. In this embodiment the opening section of the first fluid space <NUM> is designed complementary to at least a part of the free ending of a pipetting tube of a standard pipetting device, the opening section representing the connection means <NUM>. Such a pipetting device can move the first piston <NUM> either up or down, such movements being illustrated by the double arrow. The first piston <NUM> is located within the first fluid space <NUM> such that a downwards movement of the first piston <NUM> displaces fluid, in particular air, located in the first fluid space <NUM>. To avoid that said displaced fluid, instead of the mechanical coupling of the first piston <NUM> to the second piston <NUM>, provokes an actuation of the second piston <NUM> being located within the second fluid space <NUM>, a pressure equilibration means <NUM>, such as one or several holes, are arranged in the lower part of the first fluid space <NUM>.

<FIG> illustrate how a fluid of interest <NUM> gets dispensed by a displacement device <NUM>, e.g. by a displacement device designed similar to the one shown in <FIG>. The reference signs are only displayed in <FIG> for reasons of clarity. The second fluid space <NUM> of the displacement device <NUM> comprises some fluid of interest <NUM> that has previously been aspirated. By actuating the double piston <NUM> resulting in a downwards movement (indicated by the black arrow), namely towards the second chamber of the second fluid space <NUM>, a part of the aspirated fluid of interest <NUM> gets positively displaced (see <FIG>). By actuating the double piston <NUM> further to a maximum, in this embodiment until the physical blocking of the first piston <NUM>, the complete volume of the fluid of interest <NUM> gets dispensed since the second piston <NUM> is designed such that it has essentially reached the free ending of the second fluid space <NUM> when a further movement of the first piston <NUM> gets blocked (see <FIG>).

<FIG> shows an embodiment of a displacement device <NUM> according to the invention where the first piston <NUM> and the second piston <NUM> are fluid-coupled. This coupling may provide for an actuation of the second piston <NUM> in dependence on the first piston <NUM> based on pneumatic force or hydraulic force, depending on the fluid being a gas or a liquid. This fluid is represented by the small black spots located in the connection piece <NUM> arranged between the first fluid space <NUM> and the second fluid space <NUM> and provides for an operational coupling between the first piston <NUM> and the second piston <NUM> and thus ensures an actuation of the second piston <NUM> in dependence on the first piston <NUM>. When the first piston <NUM> is actuated by an actuation volume that causes a downwards movement of the first piston <NUM> by a first distance d<NUM>, fluid in the connection piece <NUM> gets displaced. The displaced fluid volume depends on the first distance d<NUM> as well as on the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the second chamber <NUM> of the first fluid space <NUM>. In case the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the first chamber <NUM> of the second fluid space <NUM> were identical to other side, the second piston <NUM> would be pushed by a second distance d<NUM> identical to the first distance d<NUM> and the volume transmission were dependent on the piston displacement area of the first piston <NUM> and the second piston <NUM> only. However, the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the first chamber <NUM> of the second fluid space <NUM> of this embodiment is not identical to the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the second chamber <NUM> of the first fluid space <NUM>. In consequence, it is also the ratio of the cross-sectional areas of the connection piece <NUM> having an impact on the volume transmission ratio. As the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the second chamber <NUM> of the first fluid space <NUM> is smaller than the cross-sectional area of the connection piece <NUM> on the side being operationally connected to the first chamber <NUM> of the second fluid space <NUM>, the second distance d<NUM> is shorter than the first distance d<NUM>. The pneumatic or hydraulic force can thus be used for linearly actuating the second piston <NUM> or for actuating and further transmitting the ratio of the actuation volume to the displacement volume.

<FIG> shows an embodiment of a displacement device <NUM> comprising a first fluid space <NUM> designed separately from a second fluid space <NUM>. The second fluid space <NUM> of this embodiment is a standard positive displacement tip. <FIG> shows the same displacement device <NUM> in assembled state. The reference signs are only displayed in <FIG> for reasons of clarity. The first piston <NUM> of the first fluid space <NUM>, which first piston displacement area A<NUM> separates the first chamber <NUM> of the first fluid space <NUM> and the second chamber <NUM> of the first fluid space <NUM>, comprises a means for coupling with the second piston <NUM> of the second fluid space <NUM>. The coupling provides for a movement of the second piston <NUM> in dependence on the first piston <NUM>. The means for coupling is illustrated by means of the narrow prolongation adjacent to the first displacement area A<NUM>. The first fluid space <NUM> comprises connection means <NUM> for getting connected to a pipetting device (not shown). The second chamber <NUM> of the first fluid space <NUM> comprises pressure equilibrium means <NUM>. The second fluid space <NUM> comprises connection means <NUM> for getting connected to the first fluid space <NUM>. Both the connection means <NUM> are preferably constructed to allow a plug connection by simply plugging the first fluid space <NUM> on the pipetting device or vice versa and the second fluid space <NUM> on the first fluid space <NUM> or vice versa. The second piston <NUM> is designed as a bar of a continuous cross-sectional area that is essentially equivalent to the cross-sectional area of the second fluid space <NUM>. In consequence, the body of the second piston <NUM> fills the first chamber <NUM> of the second fluid space <NUM>. To avoid a sliding of the second piston <NUM> through the second chamber <NUM> of the second fluid space <NUM>, the second piston <NUM> comprises a thickening. On the other hand, the first fluid space <NUM> comprises means for limiting the movement of the first piston <NUM> such as one or more protrusions located in the second chamber <NUM> of the first fluid space <NUM>.

<FIG> shows a displacement device set <NUM> comprising a first fluid space <NUM> designed separately from three different second fluid spaces <NUM>. The first fluid space <NUM> and the most left of the second fluid spaces <NUM> are designed identical to the ones shown in <FIG>. However, the set of <FIG> comprises two more second fluid spaces <NUM> that can be combined with the fist fluid space <NUM> as described based on <FIG>. Each of the second fluid spaces <NUM> comprises a second piston <NUM> with a second piston displacement area A<NUM> different in size. The second fluid space <NUM> comprises the second piston <NUM> having the largest second piston displacement area A<NUM> and the second fluid space <NUM> on the right-hand side comprises the second piston <NUM> having the smallest second piston displacement area A<NUM>. By exchanging the second fluid spaces <NUM> of the set, different volume transmission can be provided without having to exchange the complete displacement device. The smaller the second piston displacement area A<NUM>, the larger is the volume transmission.

<FIG> shows an embodiment of a displacement device <NUM> that is in particular suitable for displacing powder or suspensions. The displacement device <NUM> is in general designed like the displacement device of <FIG>. However, the second piston <NUM> is not designed as a bar of a continuous cross-sectional area but comprises three protrusions having essentially the same cross-sectional area, which is essentially equivalent to the cross-sectional area of the second fluid space <NUM>. In this embodiment, the three protrusions form two powder chambers in the second chamber <NUM> of the second fluid space <NUM>; a first one between the first protrusion and the second protrusion and a second one between the second protrusion and the third protrusion. The duty of the bottom protrusion closing the powder chamber is to avoid any loss of powder between aspiration and dispensation. Although the shown embodiment comprises three protrusions, it is enough to provide a second piston with only two protrusions to allow for a reliable aspiration and dispensation of powder or suspensions. Since the cross-sectional areas of the single protrusions are essentially identical, it is the cross-sectional area of the first protrusion that represents the second piston displacement area A<NUM>. The second piston displacement area A<NUM> is illustrated separately in the enlarged cut-out on the right-hand side.

<FIG> shows a pipetting system <NUM> comprising a pipetting device <NUM> and a displacement device <NUM> according to the invention. The pipetting device <NUM> comprises a pipetting arm <NUM>. The pipetting arm <NUM> in turn comprises a pipetting tube <NUM> which is moveable in x, y and z coordinates by the pipetting arm <NUM>. The displacement device <NUM> is removably coupled to the pipetting tube <NUM> by friction fit. The upper part of the first fluid space of the displacement device <NUM> is plugged on the free end of the pipetting tube <NUM>. Three well plates ready to receive a fluid of interest are provided on the work bench of the pipetting device <NUM>. The pipetting tube <NUM> is connected by means of a tube, i.e. the pipetting pipe <NUM>, to a means controlling the actuation volume (means not shown), such as e.g. a pressure source (e.g. of an VCP pipetting device) or a syringe pump (e.g. of a fluid pipetting device). The pipetting pipe <NUM> leads partially through the z-rod <NUM> of the pipetting arm <NUM>. The pipetting arm <NUM> and the means for controlling the volume are controlled by a common control unit (not shown).

<FIG> shows an embodiment of a displacement device <NUM> according to the invention that is coupled to a pipetting tube <NUM> of a pipetting device (not shown) in cross-section. The upper part of the first chamber <NUM> of the first fluid space <NUM> surrounds the outer surface of the pipetting tube <NUM> with its two protrusions meant to ensure a reliable friction fit. The pipette tube <NUM> is formed as an adapter <NUM>. Pressure equilibration means <NUM> are located close to the bottom of the second chamber <NUM> of the device <NUM>. A pipetting pipe <NUM> that leads through the pipetting tube <NUM> into the first chamber <NUM> of the first fluid space <NUM> of the displacement device <NUM> provides for the connection to a means for controlling the actuation volume (not shown). The second chamber <NUM> of the first fluid space <NUM>, the first chamber <NUM> of the second fluid space <NUM> and the second chamber <NUM> of the second fluid space <NUM> are also illustrated for the sake of completeness.

<FIG> shows a z-rod <NUM> of a pipetting arm of a pipetting device (not shown) and its pipetting tube <NUM> in cross-section. Such a pipetting tube <NUM> is for instance suitable for coupling with a displacement device according to the invention (not shown) and can comprise a thread working as coupling means <NUM>. The pipetting pipe <NUM> that leads through the pipetting tube <NUM> into the first chamber of the first fluid space of the displacement device provides for the connection to a means for controlling the actuation volume (not shown).

<FIG> shows a z-rod <NUM> of a pipetting arm of comprising an adapter <NUM> for coupling with a displacement device according to the invention (not shown) in cross-section. The same adapter <NUM> can be used for coupling conventional disposable pipetting tips. The displacement device is coupled directly to the pipetting tube by means of an adapter <NUM>. The pipetting pipe <NUM> can protrude from the adapter <NUM> as shown in this example. Such an adapter <NUM> may comprise a different cross-sectional diameter than the pipetting tube and/or coupling means such as protrusions or alike to provide for a better fit or even for a connection between a displacement device and a pipetting device at all.

Claim 1:
Pipetting system comprising a pipetting device (<NUM>) and a displacement device (<NUM>),
wherein said pipetting device (<NUM>) is in particular an air pipetting device or a fluid pipetting device or valve-controlled pipetting device, and
wherein said displacement device (<NUM>) comprises:
- a first fluid space (<NUM>) separated into a first chamber (<NUM>) and a second chamber (<NUM>) by a first piston displacement area (A<NUM>) of a first piston (<NUM>) being arranged in a movable manner within said first fluid space (<NUM>), said first chamber (<NUM>) of said first fluid space (<NUM>) being connectable to said pipetting device (<NUM>), said first piston (<NUM>) being actuatable by an actuation volume (Va) of working fluid of said pipetting device (<NUM>); and
- a second fluid space (<NUM>) separated into a first chamber (<NUM>) and a second chamber (<NUM>) by a second piston displacement area (A<NUM>) of a second piston (<NUM>) being arranged in a movable manner within said second fluid space (<NUM>), said second piston (<NUM>) being actuated in dependence on said first piston (<NUM>) being actuated by said actuation volume (Va), said second piston (<NUM>) being constructed to displace a displacement volume (Vd) of a fluid located within said second chamber (<NUM>) of said second fluid space (<NUM>) when being actuated in dependence on said first piston (<NUM>) being actuated by said actuation volume (Va),
wherein said actuation volume (Va) is different from said displacement volume (Vd), and
wherein said first fluid space (<NUM>) and said second fluid space (<NUM>) are removably connected, and
wherein said displacement device (<NUM>) is connected to said pipetting device (<NUM>), in particular by means of removable sticking to a pipette tube of said pipetting device (<NUM>).