WO2010082080A1

WO2010082080A1 - Multi-channel pipette guidance system

Info

Publication number: WO2010082080A1
Application number: PCT/IB2009/005010
Authority: WO
Inventors: Bernard Roussel; Stephane Guichardon; Olivier Clary
Original assignee: Gilson S.A.S.
Priority date: 2009-01-16
Filing date: 2009-01-16
Publication date: 2010-07-22

Abstract

A device for use in a multi- channel pipetting system is provided. The device includes a guidance assembly (302) that includes a piston holder (418), a first and a second rotating element (412, 414), a shaft (416), and a first and a second track (408, 410). The piston holder (418) includes a plurality of aligned notches (426), a first slot (420) extending above the plurality of aligned notches (426) and generally parallel to the plurality of aligned notches (426), and a second and a third slot (422, 424) extending generally orthogonal to the first slot (420). The first rotating element (412) is mounted in the second slot (422) and the second rotating element (414) is mounted in the third slot (424). The shaft (416) is mounted in the first slot (420) and connects the first rotating element (412) to the second rotating element (414). The first rotating element (412) is mounted to roll along the first track (408) and the second rotating element (414) is mounted to roll along the second track (410).

Description

MULTI-CHANNEL PIPETTE GUIDANCE SYSTEM

FIELD

[0001] The field of the disclosure relates generally to a multi-channel pipette.

BACKGROUND

[0002] Multi-channel pipetting systems include a multi-channel sampling pipette intended for the calibrated aspiration of liquids and the subsequent deposition of the liquids into receptacles. Sampling pipettes can be held in the hand of an operator during aspiration and dispensation of the liquid or may be included as part of an automated system. As an example, a multi-channel pipette may include a body forming a handle, in addition to a bottom part which, at its end, includes a plurality of pipette shafts on which pipette tips can be positioned. The bottom part includes a fixed body which, at its bottom end, has a plurality of pipette shafts spaced from each other in a sideways direction relative to the pipette body, with each pipette shaft including an orifice communicating with an intake chamber.

[0003] Parallel pistons are positioned in the intake chambers, and mounted at their upper ends to a piston holder that can be translated relative to the fixed body. The piston holder may be controlled by a manual or a motor-driven arrangement that causes the piston holder to rise during the liquid sampling or aspiration phase and causes the piston holder to descend during the liquid transfer phase, with the upward motion achieved, in general, by the expansion of a spring that was compressed during the downward movement.

[0004] During its movement, the piston holder carries with it the pistons that are attached to it so that the pistons are capable of simultaneous motion in a sliding movement that is usually parallel to a longitudinal central axis of the pipette. As an example, upward motion imposed on the piston holder, and therefore on the pistons, determines the volume of liquid drawn up. The volume is selected beforehand by the user, for example, using a control knob, an adjusting screw, a digital keypad, etc.

[0005] The piston holder usually includes a control rod parallel to a longitudinal central axis of the pipette and mounted to slide on the fixed body by means of two bearings spaced along the longitudinal central axis. The piston holder additionally includes a piston support head attached to the bottom end of the control rod and accommodating the top end of the pistons. In this case, the piston support head is arranged orthogonal to the longitudinal central axis of the pipette.

[0006] The precision and accuracy of the volume aspirated depends on the ability to reproduce, for each piston, the same simultaneous distance of travel for a given volume setting. However, it has been observed that during the use of a multichannel pipette, the support head of the piston holder, also known as the "rake", has a tendency to move without maintaining orthogonality with the sliding direction resulting in a slightly inclined plane determined by the lateral direction and the sliding direction. This effect, known as the "rake effect," occurs during the reciprocating motion of the piston holder and results in a difference in the distance of travel for one piston relative to another piston thereby reducing the precision and accuracy of the volume aspirated between the plurality of pistons. The rake effect may be caused by a large amount of play between the guide rod and the guide bearings, by an unsuitable shape of the return spring that is used to raise the piston holder, by inadequate stiffness of the piston holder, by an imbalance in the friction of the sealing gaskets mating with the pistons, etc.

[0007] The pipette shafts generally include a tapered external shape that can be fitted with a removable, disposable tip. Conventionally, the tips are force fitted on the shaft and held in place by friction. A longitudinal section through the inner surface of the tip is generally conical with dimensions that provide a frictional contact with the shaft sufficient to support a suitable retaining force and an acceptable leak tightness. The tip generally is ejected using an appropriate device integrated into the pipette. An illustrative tip ejection mechanism is described in French Patent No. A-2 807 342.

[0008] Fully satisfactory usage properties, however, are not obtained using existing pipette shafts with pipette tips having different designs because the force necessary to force fit the different types of pipette tips on the pipette shaft is uncertain and can be very large, because there is no means of limiting this force, because contact pressure at the sealing area may be low resulting in an uncertain and non-reproducible seal quality, and because the force to be applied to eject the tip is uncertain and can be very large if the tip was force fitted onto the shaft with a high force and insertion depth. Additionally, because the height and position of the sealing area are not sufficiently well controlled, there is no guarantee that the position of the tips is correct. This is particularly a problem using multi-channel pipettes that include several shafts in line with each other on which the corresponding number of tips is force fitted. There is no guarantee that the position of all the tips is correct, and therefore, that they all provide a satisfactory seal at the contact with the corresponding shaft.

SUMMARY

[0009] In an illustrative embodiment, a device for aspirating an identical amount of fluid in each of a plurality of channels of a multi-channel pipetting system is provided. The device includes a guidance assembly that includes a piston holder, a first and a second rotating element, a shaft, and a first and a second track. The piston holder includes a plurality of aligned notches, a first slot extending above the plurality of aligned notches and generally parallel to the plurality of aligned notches, and a second and a third slot extending generally orthogonal to the first slot. The first rotating element is mounted in the second slot and the second rotating element is mounted in the third slot. The shaft is mounted in the first slot and connects the first rotating element to the second rotating element. The first rotating element is mounted to roll along the first track and the second rotating element is mounted to roll along the second track.

[0010] Other principal features and advantages will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Illustrative embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements.

[0012] Fig. 1 shows a side view of a multi-channel pipette in accordance with an illustrative embodiment. [0013] Fig. 2 shows a front, perspective view of a multi-channel pipetting mechanism of the multi-channel pipette in accordance with an illustrative embodiment.

[0014] Fig. 3 shows a cross sectional side view of the multi-channel pipetting mechanism of Fig. 2 in accordance with an illustrative embodiment.

[0015] Fig. 4 shows an enlarged view of the cross sectional side view of the multichannel pipetting mechanism of Fig. 3 in accordance with an illustrative embodiment.

[0016] Fig. 4a shows a second enlarged view of the cross sectional side view of the multi-channel pipetting mechanism of Fig. 3 in accordance with an illustrative embodiment.

[0017] Fig. 5 shows a cross sectional front view of the multi-channel pipetting mechanism of Fig. 2 in accordance with an illustrative embodiment.

[0018] Fig. 6 shows a front, perspective view of a tip ejector of the multi-channel pipetting mechanism of Fig. 2 in accordance with an illustrative embodiment.

[0019] Fig. 7 shows a bottom view of the tip ejector of Fig. 6 in accordance with an illustrative embodiment.

[0020] Fig. 8 shows a top, perspective view of an adapter of the multi-channel pipetting mechanism of Fig. 2 in accordance with an illustrative embodiment.

[0021] Fig. 9 shows a side view of the adapter of Fig. 8 in accordance with an illustrative embodiment.

[0022] Fig. 10 shows a side, cross sectional view of the adapter of Fig. 9 in accordance with an illustrative embodiment.

[0023] Fig. 11 shows a side view of a shaft of the multi-channel pipetting mechanism of Fig. 2 in accordance with a first illustrative embodiment.

[0024] Fig. 12 shows a side, cross sectional view of the shaft of Fig. 11 in accordance with the first illustrative embodiment.

[0025] Fig. 13 shows a side view of the shaft of the multi-channel pipetting mechanism of Fig. 2 in accordance with a second illustrative embodiment. DETAILED DESCRIPTION

[0026] With reference to Fig. 1 , a side view of a multi-channel pipette 100 is shown in accordance with an illustrative embodiment. In other illustrative embodiments, any multi-channel pipetting system may be used. Multi-channel pipette 100 may be manually driven or motor driven. Multi-channel pipette 100 can be commanded to aspirate and to dispense a succession of liquid volumes into a plurality of pipette tips 106 using a control part 102 and a multi-channel pipetting mechanism 104. Different types and sizes of pipette tips may be used that accommodate various amounts of liquid. Multi-channel pipette 100 includes a number of components and subsystems that together provide various operational modes for aspirating and dispensing liquids in precise volumes. The components and subsystems may include, but are not limited to, a body case 108, a piston drive mechanism, a piston assembly, an internal power subsystem, a tip ejection mechanism, etc. In general these components and subsystems are known to those skilled in the art, and thus, will not be discussed in significant detail herein.

[0027] Control part 102 may include body case 108 which forms a handle for holding multi-channel pipette 100 in a hand of a user though in other embodiments, the multi-channel pipette may not be handheld. Body case 108 provides a comfortable external cover for a user holding multi-channel pipette 100 and protects the components of multi-channel pipette 100. Body case 108 includes, but is not limited to, a finger rest 110 that provides a bracing point, for example, for the pipette user's index finger to rest against while holding the body of multi-channel pipette 100 in the palm of the hand and while using multi-channel pipette 100 to interact with controls that control the aspiration and dispensation of the liquid.

[0028] Attachment knob 116 extends from an end of body case 108. Attachment knob 116 may include a surface that is threaded to allow mounting and dismounting of multi-channel pipetting mechanism 104 from control part 102. In the illustrative embodiment of Fig. 1 , tip ejection connector 118 mounts to multi-channel pipetting mechanism 104 and to attachment knob 116 to mount multi-channel pipetting mechanism 104 to control part 102. As used herein, the term "mount" includes join, unite, connect, associate, insert, hang, hold, affix, attach, fasten, bind, paste, secure, bolt, screw, rivet, solder, weld, mold, and other like terms. [0029] Multi-channel pipetting mechanism 104 includes a plurality of shafts 112 and a removable cover 114. A pipette tip of the plurality of pipette tips 106 is mounted to a shaft of the plurality of shafts 112. The plurality of pipette tips 106 can be press fit onto the plurality of shafts 112. The plurality of shafts 112 are spaced from each other in a lateral pipette direction orthogonal to a longitudinal axis 120 of multi-channel pipette 100. Each shaft of the plurality of shafts 112 has an orifice 122 communicating at its top end with an intake chamber 310 (shown with reference to Fig. 3), and at its bottom end with a cavity within the pipette tip of the plurality of pipette tips 106.

[0030] Multi-channel pipette 100 has a longitudinal central axis that corresponds to longitudinal axis 120 of multi-channel pipetting mechanism 104. Longitudinal axis 120 may be located to have an identical number of shafts positioned on either side of longitudinal axis 120 in the lateral direction. In general, longitudinal axis 120 is parallel to the axes of the plurality of shafts 112 and their associated pipette tip and to the sliding direction of a piston mounted in intake chamber 310 of the shaft.

[0031] With reference to Fig. 2, a multi-channel pipetting mechanism 104a is shown in accordance with a second illustrative embodiment. Control part 102 may include a control rod 200 which is configured to control an amount of liquid aspirated and dispensed through the pipette tip. Attachment knob 116a mounts multi-channel pipetting mechanism 104a to control part 102. Tip ejection connector 118a is connected to a tip ejection control part using connector 201. The tip ejection control part and connector 201 may be similar to the tip ejection mechanism described in U.S. Patent No. 7,264,779 incorporated herein by reference in its entirety.

[0032] Multi-channel pipetting mechanism 104a may further include a removable cover 114a. Removable cover 114a may include a first cover plate 202 and a second cover plate 204 which mounts to first cover plate 202. A tip ejector support 206 mounts to tip ejection connector 118a and to a tip ejector 208. In the illustrative embodiment of Fig. 2, tip ejector 208 includes a base 210, a first support 212, and a second support 600 (shown with reference to Fig. 6). First support 212 extends from a first side 214 of base 210 at a plurality of legs 216. For example, with reference to the illustrative embodiment of Fig. 2, first support 212 includes a first leg 218, a second leg 220, and a third leg 222 each of which extend from first side 214 of base 210. The plurality of legs 216 are joined at a cross bar 224. A fourth leg 226 extends from cross bar 224 on a side generally opposite the plurality of legs 216. Fourth leg 226 mounts to tip ejector support 206.

[0033] In the illustrative embodiment of Fig. 2, an adapter 228 mounts to base 210 in a direction generally opposite the plurality of legs 216. Adapter 228 is selected to provide consistent ejection of the plurality of pipette tips 106 mounted on the shafts 112. For example, adapter 228 may be selected based on the type of pipette tip mounted to the plurality of shafts 112. The tip ejection mechanism ejects the plurality of pipette tips 106 from the plurality of shafts 112 avoiding possible contamination of samples. Depression of an ejection knob drives tip ejector support 206, tip ejector 208, and adapter 228 toward the plurality of pipette tips 106 pushing the plurality of pipette tips 106 off from the plurality of shafts 112 with a consistent application force.

[0034] With reference to Fig. 3, a cross sectional side view of multi-channel pipetting mechanism 104a is shown in accordance with an illustrative embodiment. In the illustrative embodiment, there are twelve shafts though any number may be used. The piston drive mechanism of multi-channel pipette 100 may be manually controlled by a user, for example, through depression of a knob or may be controlled using a motor. The piston drive mechanism may include, but is not limited to, an actuator, control rod 200, a guide rod 300, a guidance assembly 302, a biasing element 304, and a brace 306. Guide rod 300 and brace 306 extend through an orifice 308 in removable cover 114a. Control rod 200 and guide rod 300 extend along longitudinal axis 120. Depression of control rod 200 causes a corresponding movement of guide rod 300 and guidance assembly 302 against a force exerted by biasing element 304 mounted at a first end to guide rod 300. In the illustrative embodiment of Fig. 3, biasing element 304 comprises a spring which is compressed against brace 306 when control rod 200 is depressed. When control rod 200 is released, biasing element 304 returns guide rod 300 and guidance assembly 302 to their initial position along longitudinal axis 120 causing the aspiration and dispensation of a specified volume of liquid through the plurality of pipette tips 106.

[0035] With reference to Fig. 4, an enlarged cross sectional side view of multichannel pipetting mechanism 104a is shown in accordance with an illustrative embodiment. First cover plate 202 includes a plurality of orifices 400 formed in first cover plate 202 and configured to receive the plurality of shafts 112. First cover plate 202 may further include a plurality of walls 401 and a wall 402. The plurality of walls 401 and wall 402 may be formed in first cover plate 202 and are configured to provide a stable support for the plurality of shafts 112. Second cover plate 204 may further include one or more walls to further provide a stable support for the plurality of shafts 112 on an opposed side. In an illustrative embodiment, first cover plate 202 and second cover plate 204 may be formed of molded plastic.

[0036] With reference to Fig. 4a, a further enlarged cross sectional side view of multi-channel pipetting mechanism 104a is shown in accordance with an illustrative embodiment. Multi-channel pipetting mechanism 104a includes a plurality of pistons 404. A support head 406 is mounted to each piston of the plurality of pistons 404. The support head 406 includes a dimple 407 which extends in a direction generally opposite the piston. A piston of the plurality of pistons 404 extends into intake chamber 310 and orifice 122 of a shaft of the plurality of shafts 112. The plurality of pistons 404 extend in a direction generally parallel to longitudinal axis 120 such that movement of guide rod 300 in the direction of longitudinal axis 120 causes simultaneous movement of the plurality of pistons 404 in the direction of longitudinal axis 120.

[0037] Guidance assembly 302 may include a first track 408, a second track 410, a first rotating element 412, a second rotating element 414, a shaft 416, and a piston holder 418. First track 408 and second track 410 are mounted to first cover plate 202. For example, first track 408 and second track 410 may be formed in first cover plate 202 using a molding process. First track 408 and second track 410 extend in a the direction of longitudinal axis 120. First rotating element 412 is mounted to roll along first track 408, and second rotating element 414 is mounted to roll along second track 410. Shaft 416 mounts first rotating element 412 to second rotating element 414 so that first rotating element 412 and second rotating element 414 simultaneously roll along first track 408 and second track 410, respectively. In the illustrative embodiment, guidance assembly 302 includes two rotating elements spaced in a lateral direction orthogonal to longitudinal axis 120 on either side of longitudinal axis 120. Guidance assembly 302 is provided to eliminate or reduce the rake effect during the reciprocating movement of piston holder 418 by applying an identical and simultaneous movement to the plurality of pistons 404. [0038] Guide rod 300 mounts to a first side of piston holder 418 opposite the plurality of pistons 404. Piston holder 418 may include a first slot 420, a second slot 422, a third slot 424, and a fourth slot 425. Fourth slot 425 may include a plurality of aligned notches 426 along a wall of fourth slot 425. First slot 420 extends above fourth slot 425 and is generally parallel to the plurality of aligned notches 426. Second slot 422 extends generally orthogonal to first slot 420. Third slot 424 also extends generally orthogonal to first slot 420. In the illustrative embodiment of Fig. 4a, second slot 422 and third slot 424 are positioned on either side of the plurality of aligned notches 426 and at the ends of first slot 420. However, second slot 422 and third slot 424 may be located between notches of the plurality of aligned notches 426 along first slot 420.

[0039] Each support head 406 of the plurality of pistons 404 is mounted in a notch of the plurality of aligned notches 426. The plurality of aligned notches 426 form a rake accommodating the support head 406 of the plurality of pistons 404 between its teeth. Each support head 406 of the plurality of pistons 404 is locked in translation by the plurality of aligned notches 426 in both directions of sliding movement to follow the reciprocating motion of guide rod 300. Thus, movement of guidance assembly 302 causes a corresponding and simultaneous movement of the plurality of pistons 404 producing an air displacement in intake chamber 310 of a shaft of the plurality of shafts 112 to aspirate or dispense the liquid into or out of a pipette tip of the plurality of pipette tips 106. An o-ring may be positioned in a seam in intake chamber 310 to provide sealing. The displacement imposed upon guidance assembly 302 in relation to brace 306 determines the volume of liquid aspirated/dispensed. In an illustrative embodiment, a sheet 428 may be positioned above the dimples 407 of the piston support heads 406 of the plurality of pistons 404 to provide a consistent contact surface. Shaft 416 is positioned in first slot 420. First rotating element 412 is positioned in second slot 422. Second rotating element 414 is positioned in third slot 424.

[0040] With reference to Fig. 5, a partial cross-sectional side view of multi-channel pipetting mechanism 104a is shown in accordance with an illustrative embodiment. In the illustrative embodiment of Fig. 5, first rotating element 412 and second rotating element 414 comprise a toothed wheel. Each toothed wheel is mounted in a track to roll without slipping along its corresponding track. The toothed wheels are mounted on the same axis of rotation defined by shaft 416 and are connected firmly together. The toothed wheels and shaft 416 are locked in translation with piston holder 418 in the direction of sliding movement. Shaft 416 locks the toothed wheels to each other in rotation so that during a movement of piston holder 418 in the direction of the longitudinal axis 120, the toothed wheels move simultaneously by the same distance along their respective track to apply identical movement to each piston due to the coupling in rotation of the toothed wheels and to the slip-free connection with the respective track. First track 408 and second track 410 may be of the longitudinal groove type extending parallel to longitudinal axis 120 with a contact surface that receives the toothed wheel.

[0041] In an alternative embodiment, first track 408 and/or second track 410 can be replaced by a chain that mates with first rotating element 412 and second rotating element 414. The chain may be tensioned by securing its two ends to removable cover 114a.

[0042] With reference to Figs. 6 and 7, tip ejector 208 includes base 210, first support 212, and second support 600. Second support 600 extends from a second side 602 of base 210 at a second plurality of legs 604. For example, with reference to the illustrative embodiment of Fig. 6, second support 600 includes a first leg 606, a second leg 608, and a third leg 610 each of which extend from second side 602 of base 210. The second plurality of legs 604 are joined at a cross bar 612. A fourth leg 614 extends from cross bar 612 on a side generally opposite the second plurality of legs 604. Fourth leg 614 is configured to mount to tip ejector support 206.

[0043] Base 210 includes a plurality of orifices 616 configured to receive the plurality of shafts 112. First side 214 and second side 602 include a plurality of notches 618 configured to accept adapter 228. Additional or fewer legs may be used to extend from base 210. The space between the plurality of legs 216 and the second plurality of legs 604 allows a user to view the aspiration/dispensation of fluid from the plurality of pipette tips 106 and reduces the weight of multi-channel pipette 100.

[0044] With reference to Figs. 8 and 9, adapter 228 is shown in accordance with an illustrative embodiment. Adapter 228 may include a third plurality of orifices 800 that generally align with the plurality of orifices 616 and are configured to receive the plurality of shafts 112. Adapter 228 further may include a groove 802 extending around at least a portion of the periphery of adapter 228 to facilitate alignment and mounting to tip ejector 208. Adapter 228 still further may include a plurality of clips 804 to mate with the plurality of notches 618 to further facilitate alignment and mounting to tip ejector 208 and to hold adapter 228 in place adjacent tip ejector 208. As shown with reference to Fig. 9, adapter 228 has a variable thickness. Adapter 228 is successively thicker from a center to an end to provide a more consistent ejection pressure across the plurality of pipette tips 106. Adapters having different thicknesses and orifice diameters may be used depending on the type and size of pipette tips 106 mounted to the plurality of shafts 112.

[0045] With reference to Fig. 10, a partial cross-sectional end view of adapter 228 is shown in accordance with an illustrative embodiment. A clip of the plurality of clips 804 includes a lip 1000 which extends over first side 214 and second side 602 of tip ejector 208 to hold adapter 228 in place adjacent tip ejector 208.

[0046] With reference to Figs. 11 and 12, a shaft 112a is shown in accordance with a first illustrative embodiment. Shaft 112a, according to the illustrative embodiment shown in Figs. 11 and 12, has a generally tapered outer shape to enable force fitting of a pipette tip onto shaft 112a. A pipette tip of the plurality of pipette tips 106 has an inner wall that has a tapered longitudinal section in an area in which contact is made with shaft 112a. The inner wall defines a cavity. The contact area should provide the best possible seal compatible with easy ejection of the pipette tip when the pipette tip is replaced. The configuration and dimensions of the pipette tip vary depending on the designed aspiration volume and the manufacturer. Previously, pipette tips were designed to fit a specific shaft resulting in widely varying designs across different manufactures and different types of devices even when produced by the same manufacturer. To provide additional flexibility in the selection of a pipette tip, shaft 112a comprises a plurality of stages 1100 that support the mounting a plurality of different types of pipette tips from different manufacturers and design for different types of pipetting devices.

[0047] Each stage of the plurality of stages 1100 includes an annular shoulder and a cylindrical section. The annular shoulder may be considered to extend from a cylindrical section or vice versa. A cylindrical section has a lower end and an upper end opposite the lower end. Each shaft stage has a length associated with a distance between the lower end and the upper end. Each shaft stage further has a cross-sectional diameter orthogonal to a longitudinal axis 1130 of shaft 112a. Each shaft stage extends from an adjacent shaft stage having a smaller diameter starting from a first shaft stage that includes an aspiration end 1132. Thus, the annular shoulder joins the cylindrical section of an adjacent shaft stage having a smaller diameter. As a result, the annular shoulder includes a first transition end adjacent the upper end of a shaft stage and a second transition end adjacent the lower end of the adjacent shaft stage. The first transition ends may be rounded to facilitate force fitting of the pipette tip.

[0048] A cylindrical section may have a tapered exterior surface or an exterior surface having a constant diameter. The diameter and the length of each stage may be selected so that an ejection force applied to remove the pipette tip from the shaft is consistent for a plurality of different types of pipette tips. To achieve this, the pipette tip may not contact each stage over which the pipette tip extends. Additionally, the pipette tip may extend over a subset of the plurality of stages 1100. In an illustrative embodiment, the diameter and the length of each stage are selected so that when mounted to the shaft a pipette tip extends over at least four shaft stages and contacts at least three of the at least four shaft stages.

[0049] In positioning the pipette tip onto shaft 112, a cylindrical section contacts the inner wall of the pipette tip when the pipette tip is force fitted onto shaft 112. A size of the contact area between the cylindrical section and the inner wall may vary depending on the pipette tip. The cylindrical sections maintain the pipette tip on shaft 112 more efficiently than using a conventional shaft arrangement whereby a diameter of shaft 112 is progressively and continuously reduced towards aspiration end 1132. The annular shoulder centers the pipette tip during force fitting and forms a progressive stop.

[0050] In the illustrative embodiment of Fig. 11 , a first cylindrical section 1104 extends from a first annular shoulder 1102. First cylindrical section 1104 is tapered and has a length of approximately 10 mm and a diameter of approximately 2.96 mm adjacent first annular shoulder 1102. A second cylindrical section 1108 extends from a second annular shoulder 1106. Second cylindrical section 1104 has an approximately constant diameter of approximately 4.3 mm and a length of approximately 3.5 mm. A third cylindrical section 1112 extends from a third annular shoulder 1110. Third cylindrical section 1112 has an approximately constant diameter of approximately 5.3 mm and a length of approximately 6.5 mm. A fourth cylindrical section 1116 extends from a fourth annular shoulder 1114. Fourth cylindrical section 1116 has an approximately constant diameter of approximately 5.3 mm and a length of approximately 3.0 mm. A fifth cylindrical section 1120 extends from a fifth annular shoulder 1118. Fifth cylindrical section 1120 has an approximately constant diameter of approximately 6.0 mm. A sixth cylindrical section 1124 extends from a sixth annular shoulder 1122. Sixth cylindrical section 1124 has an approximately constant diameter of approximately 8.0 mm. A seventh cylindrical section 1128 extends from a seventh annular shoulder 1126. Seventh cylindrical section 1128 has an approximately constant diameter of approximately 8.7 mm and a length of approximately 4.5 mm. Different numbers and sizes of shaft stages may be used depending on the types of pipette tips to be fitter on the shaft.

[0051] With reference to Fig. 13, a shaft 112b is shown in accordance with a second illustrative embodiment. Shaft 112b, according to the illustrative embodiment shown in Fig. 13, has a generally tapered outer shape to enable force fitting of a pipette tip onto shaft 112b. Shaft 112b comprises a second plurality of stages 1300. In the illustrative embodiment of Fig. 13, shaft 112b comprises ten shaft stages having diameters varying from approximately 5.0 mm to approximately 8.7 mm and lengths from approximately 1.0 mm to approximately 27.5 mm.

[0052] Using the annular shoulder, the geometry of the contact between the pipette tip and shaft 112a, 112b is more reliable because the quality of this contact becomes much more dependent on the force applied by the user during the force fitting operation of the pipette tip. A high fitting force does not cause significantly greater penetration of shaft 112a, 112b into the pipette tip than using a lower fitting force largely due to the existence of the stop provided by the annular shoulder(s) contacted by the pipette tip. As a result, when it is required to eject the pipette tip from shaft 112, the ejection force is generally equal to a clearly determined value. The fitting force does not have to be determined more precisely, yet a successful seal and ejection are more easily guaranteed. Shaft 112a, 112b can be used with single-channel or multi-channel pipettes.

[0053] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more".

[0054] The foregoing description of Illustrative embodiments of the invention have been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A device for aspirating an identical amount of fluid in each of a plurality of channels of a multi-channel pipetting system, the device comprising: a body; a guidance assembly comprising a piston holder comprising a plurality of aligned notches; a first slot extending above the plurality of aligned notches and generally parallel to the plurality of aligned notches; a second slot extending generally orthogonal to the first slot; and a third slot extending generally orthogonal to the first slot; a first rotating element mounted in the second slot; a second rotating element mounted in the third slot; and a shaft mounted in the first slot and connecting the first rotating element to the second rotating element; a first track mounted to the body and extending in a first direction; and a second track mounted to the body and extending parallel to the first direction, wherein the first rotating element is mounted to roll along the first track and the second rotating element is mounted to roll along the second track; a plurality of shafts mounted to the body, wherein each of the plurality of shafts includes an orifice connected to an intake chamber; a plurality of pistons wherein a support head mounted to each of the plurality of pistons is mounted in a notch of the plurality of aligned notches, wherein a piston of the plurality of pistons extends into the intake chamber of a shaft of the plurality of shafts; and a guide rod extending through a body orifice in the body and mounted to the piston holder on a side opposite the plurality of aligned notches wherein movement of the guide rod in the first direction causes simultaneous movement of the plurality of pistons in the first direction.

2. The device of claim 1 , wherein the first track and the second track are positioned on either side of a longitudinal central axis of the body.

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3. The device of claim 2, wherein the first track and the second track are positioned an equal distance from the longitudinal central axis of the body.

4. The device of claim 2, wherein the first track and the second track are at the two ends of the piston holder.

5. The device of claim 1 , wherein the first rotating element comprises a toothed wheel and the first track mates with the toothed wheel.

6. The device of claim 5, wherein the first rotating element comprises a toothed wheel and the first track comprises a chain that mates with the toothed wheel.

7. The device of claim 1 , wherein the first track and the second track are formed in the body.

8. The device of claim 1 , wherein the body comprises a first cover plate and a second cover plate mounted to the second cover plate, wherein the first cover plate comprises a plurality of orifices formed in the first cover plate and configured to receive the plurality of shafts.

9. The device of claim 8, wherein the body further comprises a plurality of walls formed in the first cover plate and configured to receive the plurality of shafts.

10. The device of claim 9, wherein the body further comprises a second plurality of walls formed in the second cover plate and configured to receive the plurality of shafts.

11. The device of claim 8, further comprising a tip ejector mounted to the body, the tip ejector comprising a base comprising a second plurality of orifices configured to receive the plurality of shafts, a first support extending from the base and comprising a first plurality of legs, and a second support extending from the base and comprising a second plurality of legs.

12. The device of claim 11 , further comprising an adapter mounted to the base of the tip ejector, the adapter comprising a third plurality of orifices configured to receive the plurality of shafts.

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13. The device of claim 1 , wherein the shaft comprises at least four shaft stages wherein each shaft stage comprises: a cylindrical section having a lower end, an upper end opposite the lower end, a diameter of a cross section orthogonal to a longitudinal axis of the shaft, and a length between the upper end and the lower end; and an annular shoulder including a transition end adjacent the upper end; wherein a shaft stage extends from the annular shoulder of an adjacent shaft stage having a smaller diameter; and further wherein the diameter and the length of each stage are selected so that when mounted to the shaft a pipette tip extends over the at least four shaft stages and contacts at least three of the at least four shaft stages.

14. The device of claim 13, wherein the diameter and the length of each stage are further selected so that an ejection force applied to remove the pipette tip from the shaft is consistent for a plurality of different types of pipette tips.

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