Abstract
A displacement device for displacing a displacement volume is disclosed. The device has a first fluid space and a second fluid space. A first piston is arranged in a movable manner within the first fluid space. The first fluid space is connectable to a pipetting device. The first piston is actuatable by an actuation volume of air or of liquid provided by the pipetting device. A 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 fluid space when the second piston is actuated. The second piston is actuated in dependence on the first piston that is actuated by the actuation volume. The actuation volume is different from the displacement volume, and a pipetting system has a displacement device and a method of displacing a displacement volume.
Claims
1. A pipetting system comprising a pipetting device (60) and a displacement device (1), wherein said pipetting device (60) is in particular an air pipetting device and/or a fluid pipetting device and/or an VCP pipetting device, wherein said displacement device (1) comprises a first fluid space (11) separated into a first chamber (111) and a second chamber (112) by the first piston displacement area (A.sub.1) of a first piston (21) being arranged in a movable manner within said first fluid space (11), said first chamber (111) of said first fluid space (11) being connectable to a pipetting device, said first piston (21) being actuatable by an actuation volume (V.sub.a) of working fluid of said pipetting device; and a second fluid space (12) separated into a first chamber (121) and a second chamber (122) by the second piston displacement area (A.sub.2) of a second piston (22) being arranged in a movable manner within said second fluid space (12), said second piston (22) being constructed to displace a displacement volume (V.sub.d) of a fluid located within said second chamber (122) of said second fluid space (12) when being actuated in dependence on said first piston (21) being actuated by said actuation volume (V.sub.a); wherein said actuation volume (V.sub.a) is different from said displacement volume (V.sub.d), and wherein said displacement device (1) is connected to said pipetting device (60), in particular by means of removable sticking to a pipette tube of said pipetting device.
2. The pipetting system according to claim 1, wherein said first piston (21) is constructed to displace a first volume (V.sub.1) of a fluid located within said second chamber (112) of said first fluid space (11), said first volume (V.sub.1) being in particular of equal size than said actuation volume (V.sub.a).
3. The pipetting system according to claim 1, wherein said actuation volume (V.sub.a) is larger than said displacement volume (V.sub.d), in particular between 10 to 1000 times, further in particular between 50 to 500 times.
4. The pipetting system according to claim 1, wherein said first piston (21) is constructed to cover a first distance (d.sub.1) when being actuated by the actuation volume (V.sub.a) of the working fluid of said pipetting device, which first distance (d.sub.1) is identical to a second distance (d.sub.2) covered by said second piston (22) when being actuated in dependence on said first piston (21).
5. Method A method for displacing a displacement volume (V.sub.d) of a fluid, said method comprising: moving a first piston (21) being arranged in a movable manner within a first fluid space (11), said first fluid space (11) being separated into a first chamber (111) and a second chamber (112) by a first piston displacement area (A.sub.1) of said first piston (21), wherein said moving of said first piston (21) is actuated by an actuation volume (V.sub.a) of a working fluid of a pipetting device, moving a second piston (22) being arranged in a movable manner within a second fluid space (12), said second fluid space (12) being separated into a first chamber (121) and a second chamber (122) by a second piston displacement area (A.sub.2) of said second piston (22), such that a displacement volume (V.sub.d) of a fluid located within said second chamber (122) of said second fluid space (12) is displaced, wherein said moving of said second piston (22) is actuated in dependence on moving said first piston (21) being actuated by said actuation volume (V.sub.a), wherein said actuation volume (V.sub.a) is different from said displacement volume (V.sub.d).
6. The method according to claim 5, wherein said moving a first piston (21) being arranged in a movable manner within a first fluid space (11) is performed such that a first volume (V.sub.1) of a fluid located within said second chamber (112) of said first fluid space (11) is displaced.
7. The method according to claim 5, further comprising: connecting said first chamber (111) of said first fluid space (11) to a pipetting device, in particular by means of removable sticking said first chamber (111) to a pipette tube of said pipetting device.
8. The method according to claim 5, wherein said moving of said second piston (22) comprises actuating said second piston (22) by at least one of the following: mechanical coupling; magnetic force; pneumatic force; hydraulic force.
9. A displacement device (1) for a pipetting system according to claim 1, the displacement device (1) comprising: a first fluid space (11) separated into a first chamber (111) and a second chamber (112) by the first piston displacement area (A.sub.1) of a first piston (21) being arranged in a movable manner within said first fluid space (11), said first chamber (111) of said first fluid space (11) being connectable to a pipetting device, said first piston (21) being actuatable by an actuation volume (V.sub.a) of working fluid of said pipetting device; and a second fluid space (12) separated into a first chamber (121) and a second chamber (122) by the second piston displacement area (A.sub.2) of a second piston (22) being arranged in a movable manner within said second fluid space (12), said second piston (22) being constructed to displace a displacement volume (V.sub.d) of a fluid located within said second chamber (122) of said second fluid space (12) when being actuated in dependence on said first piston (21) being actuated by said actuation volume (V.sub.a); wherein said actuation volume (V.sub.a) is different from said displacement volume (V.sub.d).
10. The displacement device (1) according to claim 9, wherein said first piston (21) is constructed to displace a first volume (V.sub.1) of a fluid located within said second chamber (112) of said first fluid space (11), said first volume (V.sub.1) being in particular of equal size than said actuation volume (V.sub.a).
11. The displacement device (1) according to claim 9, wherein said second piston (22) is a positive displacement piston.
12. The displacement device (1) according to claim 9, wherein the actuation of said second piston (22) in dependence on said first piston (21) is based on at least one of the following: mechanical coupling; magnetic force; pneumatic force; hydraulic force.
13. The displacement device (1) according to claim 9, wherein said first piston (21) is mechanically connected to said second piston (22), in particular removably connected or permanently connected.
14. The displacement device (1) according to claim 9, wherein said first fluid space (11) is connected to said second fluid space (12), in particular said second chamber (112) of said first fluid space (11) to said first chamber (121) of said second fluid space (12).
15. The displacement device (1) according to claim 14, wherein said first fluid space (11) and said second fluid space (12) are removably connected or permanently connected.
16. The displacement device (1) according to claim 9, wherein said second fluid space (12) is at least in parts formed by a standard positive displacement tip.
17. The displacement device (1) according to claim 14, wherein the first piston (21) controls the movement of the second piston (22) such that the second piston (22) cannot enter the second chamber (112) of the first fluid space (11).
18. The displacement device (1) according to claim 9, wherein said second chamber (112) of said first fluid space (11) and/or said first chamber (121) of said second fluid space (12) comprises a pressure equilibrium means (40).
19. The displacement device (1) according to claim 9, wherein said actuation volume (V.sub.a) is larger than said displacement volume (V.sub.d), in particular between 10 to 1000 times, further in particular between 50 to 500 times.
20. The displacement device (1) according to claim 9, wherein said first piston (21) covers a first distance (d.sub.1) when being actuated by the actuation volume (V.sub.a) of the working fluid of said pipetting device, which first distance (d.sub.1) is identical to a second distance (d.sub.2) covered by said second piston (22) when being actuated in dependence on said first piston (21).
21. The displacement device (1) according to claim 9, wherein said first piston displacement area (A.sub.1) is different in size from said second piston displacement area (A.sub.2).
22. The displacement device (1) according to claim 21, wherein said first piston displacement area (A.sub.1) is larger than said second piston displacement area (A.sub.2), in particular between 10 to 1000 times, further in particular between 50 to 500 times.
23. The displacement device (1) according to claim 9, wherein said first fluid space (11), in particular said first chamber (111) of said first fluid space (11) and/or said second chamber (112) of said first fluid space (11), and/or said second fluid space (12), in particular said first chamber (121) of said second fluid space (12) and/or said second chamber (122) of said second fluid space (12) comprise an electrode that is constructed to form a measuring capacitor together with a further electrode.
24. A displacement device set comprising at least one displacement device (1) according to claim 9 and at least one further second fluid space (12) being designed combinable with said first fluid space (11) of said at least one displacement device (1), wherein said first fluid space (11) of said at least one displacement device (1) is designed separately from said second fluid space (12) of said at least one displacement device (1), and wherein said at least one further second fluid space (12) being separated into a first chamber (121) and a second chamber (122) by the second piston displacement area (A.sub.2) of a second piston (22) arranged in a movable manner within said further second fluid space (12) comprises a second piston displacement area (A.sub.2) being different from the second piston displacement area (A.sub.2) of the second fluid space (12) of said at least one displacement device (1).
25. A method of translating a first fluid volume to a second fluid volume, comprising the steps of: providing the pipetting system according to claim 1; and translating an actuation volume (V.sub.a) to a displacement volume (V.sub.d).
26. A method of displacing a displacement volume (V.sub.d), comprising the step of providing the pipetting system according to claim 1, wherein the pipetting device (60) is constructed to displace an actuation volume (V.sub.a), said actuation volume (V.sub.a) having a different volume than said displacement volume (V.sub.d).
Description
[0061] The invention shall now be further exemplified with the help of figures. The figures schematically show:
[0062] FIG. 1a a displacement device according to the invention;
[0063] FIG. 1b the displacement device of FIG. 1a displacing a fluid of interest;
[0064] FIG. 2a an embodiment of a displacement device according to the invention;
[0065] FIG. 2b a cross-sectional top view of the displacement device of FIG. 2a;
[0066] FIG. 3a a further embodiment of a displacement device according to the invention;
[0067] FIG. 3b the displacement device of FIG. 3a displacing a fluid of interest;
[0068] FIG. 4a a even further embodiment of a displacement device according to the invention;
[0069] FIG. 4b the double piston of the displacement device of FIG. 4a;
[0070] FIG. 5a the displacement device of FIG. 4a having a fluid of interest aspirated;
[0071] FIG. 5b the displacement device of FIG. 4a displacing a fluid of interest;
[0072] FIG. 5c the displacement device of FIG. 4a further displacing a fluid of interest;
[0073] FIG. 6 an embodiment of a displacement device according to the invention;
[0074] FIG. 7a an embodiment of a displacement device in two-piece design;
[0075] FIG. 7b the displacement device of FIG. 7a in assembled state;
[0076] FIG. 8 a displacement device set;
[0077] FIG. 9 an embodiment of a displacement device for displacing powder;
[0078] FIG. 10 a pipetting system comprising a pipetting device and a displacement device according to the invention;
[0079] FIG. 11 an embodiment of a displacement device according to the invention coupled to a pipetting tube of a pipetting device;
[0080] FIG. 12a a pipetting arm having a pipetting tube suitable for coupling with a displacement device according to the invention; and
[0081] FIG. 12b a pipetting arm comprising an adapter for coupling with a displacement device according to the invention.
[0082] FIG. 1a shows a displacement device 1 according to the invention. The displacement device 1 comprises a first fluid space 11 and a second fluid space 12. In the illustrated embodiment, the first fluid space 11 and the second fluid space 12 are designed separately and are thus not in fluid-connection or any other physical connection. The first fluid space 11 is separated into a first chamber 111 and a second chamber 112 by a first piston displacement area Ai of a first piston 21. The second fluid space 12 is also separated into a first chamber 121 and a second chamber 122 by a second piston displacement area A.sub.2 of a piston, namely the second piston 22.
[0083] The first chamber 111 of the first fluid space 11 is connectable to a pipetting device 60 drawn in dashed lines to indicate that the pipetting device 60 is not part of the displacement device 1. The pipetting device 60 is, for instance, an air pipetting device or a fluid pipetting device. The second chamber 112 of the first fluid space 11 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 112 of the first fluid space 11 may comprise a pressure equilibrium means (not shown here) to avoid any negative impact on the mobility of the first piston 21. 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 112 of the first fluid space 11, or a valve. Alternatively, the second chamber 112 of the first fluid space 11 can partially be made of an elastic material also allowing for a pressure equilibrium.
[0084] To move the first piston 21, 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 111 of the first fluid space 11. By removing working fluid of the pipetting device from the first chamber 111, the first piston 21 is lifted such that the volume of the second chamber 112 is increased and the volume of the first chamber 111 is decreased. By guiding working fluid of the pipetting device into the first chamber 111, the first piston is pushed downwards such that the volume of the second chamber 112 is decreased and the volume of the first chamber 111 is increased.
[0085] Since the actuation of the second piston 22 depends on the first piston 21, and therefore also on the movement of the first piston 21, the guiding of working fluid of the pipetting device into or the removing of working fluid of the pipetting device from the first chamber 111 of the first fluid space 11 provokes indirectly via the first piston 21 a movement of the second piston 22. A lift of the second piston 21 leads to a decrease of the first chamber 121 of the second fluid space 12 and an increase of the second chamber 122 of the second fluid space 12. When the second chamber 122 of the second fluid space 12 is in fluid-connection to a fluid of interest 50 (e.g. an analytical sample or any liquid consumable) while the second piston 22 is lifted, a volume of the fluid of interest 50 is aspirated. When the second chamber 122 of the second fluid space 12 comprises some fluid of interest 50 while the second piston 22 is pushed down, a volume of the fluid of interest 50 is dispensed, i.e. displaced. FIG. 1b illustrates the displacement of the fluid of interest 50.
[0086] In the shown embodiment, the first piston 21 and second piston 22 are magnetically coupled such that a downward movement of the first piston 21 provokes an identical downward movement, i.e. a simultaneous movement covering the same distance, of the second piston 22.
[0087] Since the first piston 21 comprises a first piston displacement area A.sub.1 (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.sub.2 of the second piston 22 (cross sectional area also indicated schematically by a double arrow), a smaller volume is displaced when the first piston 21 is moved downwards by a certain distance compared to when the second piston 22 is moved by the same certain distance in the same direction. The displacement device 1 does therefore provide for a transformation of fluid volumes. In the shown embodiment, the first piston displacement area A.sub.1 of the first piston 21 is 10 times smaller than the second piston displacement area A.sub.2 of the second piston 22. This means that when the pipetting device 60 is set to displace a volume of e.g. 1 mL and in consequence moves the first piston 21 by e.g. 2 cm, the second piston 22 displaces a volume of 10 mL when being moved by 2 cm. The resulting transformation ratio is thus 1:10 and a pipetting device 60 that is designed to aspirate and dispense sample volumes of between 1 mL to 10 mL is capable by means of the displacement device 1 of this embodiment to aspirate and dispense volumes of 10 mL to 100 ml without the need of any adjustment of the pipetting device 60 at all.
[0088] FIG. 2a shows an embodiment of a displacement device 1 according to the invention. Its general set-up is comparable to the set-up of the displacement device shown in FIGS. 1a and 1b. However, the first fluid space 11 of the displacement device 1 illustrated here is partially surrounded by the second fluid space 12, although there is no fluid-connection between the first fluid space 11 and the second fluid space 12. A physical connection between the first fluid space 11 and the second fluid space 12 can exist but is not necessary. To indicate that the section surrounded by the second fluid space 12 is normally not visible, the first fluid space 11 and the first piston 21 are drawn in dashed lines. The first piston 21 separating the first chamber 111 of the first fluid space 11 from the second chamber 112 of the first fluid space 11 and the second piston 22 separating the first chamber 121 of the second fluid space 12 from the second chamber 122 of the second fluid space 12 are in alignment representing a simultaneous movement of the two pistons 21, 22 and thus one way of moving the second piston 22 in dependence on moving the first piston 21, the first piston 21 being actuatable by the pipetting device 60. FIG. 2b shows a top view of a cross section along section A-A of the displacement device 1 of FIG. 2a in order to demonstrate how the first fluid space 11 is surrounded or enclosed by the second fluid space 12. 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 11 and the second fluid space 12 of the shown embodiment of the displacement device 1 comprise both a rectangular cross section.
[0089] FIG. 3a shows a further embodiment of a displacement device 1 according to the invention, the displacement device 1 having aspirated some fluid of interest 50. The displacement device 1 comprises a first fluid space 11 being in fluid-connection with a second fluid space 12. The first fluid space 11 is divided into two chambers by a first piston displacement area A.sub.1 of a first piston 21, the second fluid space 12 is divided into two chambers by a second piston displacement area A2 of a second piston 22. The first piston 21 and the second piston 22 are mechanically coupled such that an actuation of the first piston 21 by a fluid (e.g. gas, such as air, and/or liquid, such as water) provided by a pipetting device 60 provokes an actuation of the second piston 22. The first fluid space 11 comprises a pressure equilibrium means 40 that is arranged on the one hand such that a fluid getting displaced by a downwards movement of the first piston 21 does not influence the actuation of the second piston 22 and on the other hand such that an upwards movement of the first piston 21 is not blocked by the creation of underpressure. Furthermore, the first fluid space 11 comprises means for limiting the movement of the first piston 21 (and thus for limiting the movement of the second piston 22 due to their mechanical coupling) in form of a protrusion located in the first chamber of the first fluid space 11. The protrusion prevents a further uplifting of the first piston 21 that would cause the second piston 22 to leave the second fluid space 12 and enter the first fluid space 11. Such a means for limiting the movement could e.g. also be arranged at the threshold of the first fluid space 11 to the second fluid space 12 and thus directly hindering the movement of the second piston 22. It is also possible to implement means for limiting the movement of the first piston 21 in both the first chamber and the second chamber of the first fluid space 11 in order to e.g. define a maximum first volume and thus being able to transfer friction-independent always the same maximum volume. FIG. 3b illustrates that the displacement device 1 of this embodiment is designed for displacing a displacement volume V.sub.d that is smaller than the actuation volume V.sub.a provided by the pipetting device 60.
[0090] FIG. 4a shows an even further embodiment of a displacement device 1 according to the invention. The double piston 20 of the displacement device 1 with the first piston displacement area A.sub.1 of its first piston 21 and the second piston displacement area A.sub.2 of its second piston 22 is shown in FIG. 4b. The cross-sectional areas belonging to the displacement areas are schematically illustrated by double arrows. The first piston displacement area A.sub.1 represents the largest cross-sectional area of the first piston 11, wherein the second piston displacement area A.sub.2 represents the lower surface of the second piston 22 since it comprises a constant cross-sectional area. The displacement device 1 comprises a first fluid space 11 and a second fluid space 12 being connected to each other, both fluid-connected and physically connected. The first fluid space 11 has a cross-sectional area being larger than the cross-sectional area of the second fluid space 12. The cross-sectional area of the first fluid space 11 and the cross-sectional area of the second fluid space 12 are essentially identical to the first piston displacement area A.sub.1 of the first piston 21 and the second piston displacement area A.sub.2 of the second piston 22 respectively. The rigid connection bar connecting the first piston 21 to the second piston 22 make sure that a movement by a certain distance in one direction of the first piston 21 provokes a predetermined movement of the second piston 22 by the same certain distance in the same direction. In other words, the second piston 22 is mechanically actuated by the first piston 21. The first piston 21 on the other hand is actuated by a fluid provided by a pipetting device (not shown here). The displacement device 1 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 1 comprises connection means 30. In this embodiment the opening section of the first fluid space 11 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 30. Such a pipetting device can move the first piston 21 either up or down, such movements being illustrated by the double arrow. The first piston 21 is located within the first fluid space 11 such that a downwards movement of the first piston 21 displaces fluid, in particular air, located in the first fluid space 11. To avoid that said displaced fluid, instead of the mechanical coupling of the first piston 21 to the second piston 22, provokes an actuation of the second piston 22 being located within the second fluid space 12, a pressure equilibration means 40, such as one or several holes, are arranged in the lower part of the first fluid space 11.
[0091] FIG. 5a to FIG. 5c illustrate how a fluid of interest 50 gets dispensed by a displacement device 1, e.g. by a displacement device designed similar to the one shown in FIG. 4a. The reference signs are only displayed in FIG. 5a for reasons of clarity. The second fluid space 12 of the displacement device 1 comprises some fluid of interest 50 that has previously been aspirated. By actuating the double piston 20 resulting in a downwards movement (indicated by the black arrow), namely towards the second chamber of the second fluid space 12, a part of the aspirated fluid of interest 50 gets positively displaced (see FIG. 5b). By actuating the double piston 20 further to a maximum, in this embodiment until the physical blocking of the first piston 11, the complete volume of the fluid of interest 50 gets dispensed since the second piston 22 is designed such that it has essentially reached the free ending of the second fluid space 12 when a further movement of the first piston 11 gets blocked (see FIG. 5c).
[0092] FIG. 6 shows an embodiment of a displacement device 1 according to the invention where the first piston 21 and the second piston 22 are fluid-coupled. This coupling may provide for an actuation of the second piston 22 in dependence on the first piston 21 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 70 arranged between the first fluid space 11 and the second fluid space 12 and provides for an operational coupling between the first piston 21 and the second piston 22 and thus ensures an actuation of the second piston 22 in dependence on the first piston 21. When the first piston 21 is actuated by an actuation volume that causes a downwards movement of the first piston 21 by a first distance d.sub.1, fluid in the connection piece 70 gets displaced. The displaced fluid volume depends on the first distance d.sub.1 as well as on the cross-sectional area of the connection piece 70 on the side being operationally connected to the second chamber 112 of the first fluid space 11. In case the cross-sectional area of the connection piece 70 on the side being operationally connected to the first chamber 121 of the second fluid space 12 were identical to other side, the second piston 22 would be pushed by a second distance d.sub.2 identical to the first distance d.sub.1 and the volume transmission were dependent on the piston displacement area of the first piston 21 and the second piston 22 only. However, the cross-sectional area of the connection piece 70 on the side being operationally connected to the first chamber 121 of the second fluid space 12 of this embodiment is not identical to the cross-sectional area of the connection piece 70 on the side being operationally connected to the second chamber 112 of the first fluid space 11. In consequence, it is also the ratio of the cross-sectional areas of the connection piece 70 having an impact on the volume transmission ratio. As the cross-sectional area of the connection piece 70 on the side being operationally connected to the second chamber 112 of the first fluid space 11 is smaller than the cross-sectional area of the connection piece 70 on the side being operationally connected to the first chamber 121 of the second fluid space 12, the second distance d.sub.2 is shorter than the first distance d.sub.1. The pneumatic or hydraulic force can thus be used for linearly actuating the second piston 22 or for actuating and further transmitting the ratio of the actuation volume to the displacement volume.
[0093] FIG. 7a shows an embodiment of a displacement device 1 comprising a first fluid space 11 designed separately from a second fluid space 12. The second fluid space 12 of this embodiment is a standard positive displacement tip. FIG. 7b shows the same displacement device 1 in assembled state. The reference signs are only displayed in FIG. 7a for reasons of clarity. The first piston 21 of the first fluid space 11, which first piston displacement area A.sub.1 separates the first chamber 111 of the first fluid space 11 and the second chamber 112 of the first fluid space 11, comprises a means for coupling with the second piston 22 of the second fluid space 12. The coupling provides for a movement of the second piston 22 in dependence on the first piston 21. The means for coupling is illustrated by means of the narrow prolongation adjacent to the first displacement area A.sub.1. The first fluid space 11 comprises connection means 30 for getting connected to a pipetting device (not shown). The second chamber 112 of the first fluid space 11 comprises pressure equilibrium means 40. The second fluid space 12 comprises connection means 30 for getting connected to the first fluid space 11. Both the connection means 30 are preferably constructed to allow a plug connection by simply plugging the first fluid space 11 on the pipetting device or vice versa and the second fluid space 12 on the first fluid space 11 or vice versa. The second piston 22 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 12. In consequence, the body of the second piston 12 fills the first chamber 121 of the second fluid space 12. To avoid a sliding of the second piston 22 through the second chamber 122 of the second fluid space 12, the second piston 22 comprises a thickening. On the other hand, the first fluid space 11 comprises means for limiting the movement of the first piston 21 such as one or more protrusions located in the second chamber 112 of the first fluid space 11.
[0094] FIG. 8 shows a displacement device set 1 comprising a first fluid space 11 designed separately from three different second fluid spaces 12. The first fluid space 11 and the most left of the second fluid spaces 12 are designed identical to the ones shown in FIG. 7a and FIG. 7b. However, the set of FIG. 8 comprises two more second fluid spaces 12 that can be combined with the first fluid space 11 as described based on FIG. 7a and FIG. 7b. Each of the second fluid spaces 12 comprises a second piston 22 with a second piston displacement area A.sub.2 different in size. The second fluid space 12 comprises the second piston 22 having the largest second piston displacement area A.sub.2 and the second fluid space 12 on the right-hand side comprises the second piston 22 having the smallest second piston displacement area A.sub.2. By exchanging the second fluid spaces 12 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.sub.2, the larger is the volume transmission.
[0095] FIG. 9 shows an embodiment of a displacement device 1 that is in particular suitable for displacing powder or suspensions. The displacement device 1 is in general designed like the displacement device of FIG. 5a to FIG. 5c. However, the second piston 22 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 12. In this embodiment, the three protrusions form two powder chambers in the second chamber 122 of the second fluid space 12; 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.sub.2. The second piston displacement area A.sub.2 is illustrated separately in the enlarged cut-out on the right-hand side.
[0096] FIG. 10 shows a pipetting system 100 comprising a pipetting device 60 and a displacement device 1 according to the invention. The pipetting device 60 comprises a pipetting arm 62. The pipetting arm 62 in turn comprises a pipetting tube 61 which is moveable in x, y and z coordinates by the pipetting arm 62. The displacement device 1 is removably coupled to the pipetting tube 61 by friction fit. The upper part of the first fluid space of the displacement device 1 is plugged on the free end of the pipetting tube 61. Three well plates ready to receive a fluid of interest are provided on the work bench of the pipetting device 60. The pipetting tube 61 is connected by means of a tube, i.e. the pipetting pipe 65, 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 65 leads partially through the z-rod 64 of the pipetting arm 62. The pipetting arm 62 and the means for controlling the volume are controlled by a common control unit (not shown).
[0097] FIG. 11 shows an embodiment of a displacement device 1 according to the invention that is coupled to a pipetting tube 61 of a pipetting device (not shown) in cross-section. The upper part of the first chamber 111 of the first fluid space 11 surrounds the outer surface of the pipetting tube 61 with its two protrusions meant to ensure a reliable friction fit. The pipette tube 61 is formed as an adapter 63. Pressure equilibration means 40 are located close to the bottom of the second chamber 112 of the device 1. A pipetting pipe 65 that leads through the pipetting tube 61 into the first chamber 111 of the first fluid space 11 of the displacement device 1 provides for the connection to a means for controlling the actuation volume (not shown). The second chamber 112 of the first fluid space 11, the first chamber 121 of the second fluid space 12 and the second chamber 122 of the second fluid space 12 are also illustrated for the sake of completeness.
[0098] FIG. 12a shows a z-rod 64 of a pipetting arm of a pipetting device (not shown) and its pipetting tube 61 in cross-section. Such a pipetting tube 61 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 30. The pipetting pipe 65 that leads through the pipetting tube 61 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).
[0099] FIG. 12b shows a z-rod 64 of a pipetting arm of comprising an adapter 63 for coupling with a displacement device according to the invention (not shown) in cross-section. The same adapter 63 can be used for coupling conventional disposable pipetting tips. The displacement device is coupled directly to the pipetting tube by means of an adapter 63. The pipetting pipe 65 can protrude from the adapter 63 as shown in this example. Such an adapter 63 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.
REFERENCE SIGNS
[0100] 1 Positive displacement device [0101] 11 First fluid space [0102] 111 First chamber of first fluid space [0103] 112 Second chamber of first fluid space [0104] 12 Second fluid space [0105] 121 First chamber of second fluid space [0106] 122 Second chamber of second fluid space [0107] 20 Double piston [0108] 21 First piston [0109] 22 Second piston [0110] 30 Connection means [0111] 40 Pressure equilibration means [0112] 50 Fluid of interest [0113] 60 Pipetting device [0114] 61 Pipetting tube [0115] 62 Pipetting arm [0116] 63 Adapter [0117] 64 Z-rod of pipetting arm [0118] 65 Pipetting pipe [0119] 70 Connection piece [0120] 100 System [0121] A.sub.1 First piston displacement area [0122] A.sub.2 Second piston displacement area [0123] d.sub.1 First distance [0124] d.sub.2 Second distance [0125] V.sub.a Actuation volume [0126] V.sub.d Displacement volume [0127] V.sub.1 First volume
