WO2022018434A1

WO2022018434A1 - Tip ejector block and multi-channel laboratory tool

Info

Publication number: WO2022018434A1
Application number: PCT/GB2021/051865
Authority: WO
Inventors: Christoph Yves SADÉE
Original assignee: The Francis Crick Institute Limited
Priority date: 2020-07-24
Filing date: 2021-07-21
Publication date: 2022-01-27
Also published as: GB202011501D0; GB2597505A

Abstract

A tip ejector block (22), for ejecting tips (10) from shafts (8) of a multi-channel laboratory tool (2), comprises apertures (42) for receiving the shafts (8), spaced along a first axis at regular intervals of a predetermined spacing interval. A front end surface (24) comprises contact surface portions (46) each surrounding a respective aperture (42) for ejecting the tip from a corresponding shaft when in use. In at least one configuration: the apertures (42) comprise first and second subsets (62, 64) of apertures interleaved in an alternating pattern, and when the tip ejector block is moved along a second axis perpendicular to the first axis with the front end surface (24) facing a direction of travel, the contact surface portions (46) for the first subset (62) of apertures reach a given position along the second axis before the contact surface portions (46) for the second subset (64) of apertures.

Description

TIP EJECTOR BLOCK AND MULTI-CHANNEL LABORATORY TOOL

The present technique relaters to the field of laboratory tools.

Scientific researchers may use a multi-channel laboratory tool to conduct scientific experiments on samples disposed within wells, tubes or other vessels. The multi-channel laboratory tool may have a number of tip-carrying shafts. In use, disposable tips are fitted over the ends of the shafts of the tool, and the tips can be used to carry samples such as (liquid) reagents, fluid samples or biological material trapped on magnetic beads (for example), to transfer the samples between vessels. Once the use of the tips is complete then the tips can be ejected from the shafts using an ejector mechanism of the multi-channel laboratory tool. An example of such a multi-channel laboratory tool is a pipette which may have a fluid aspirating mechanism for drawing fluid into the tips at the end of the shafts and expelling fluid from the tips. Another example of such a multi-channel laboratory tool may be a magnetic bead carrying device where the shafts comprise magnetic rods which can be used to attract magnetic beads onto the disposable tips and then the rods can be retracted to cause the magnetic beads to fall off the tips. Such a multi-channel laboratory tool can be useful for speeding up experiments and improve reproducibility because, in comparison to a single-channel tool, the multi-channel laboratory tool is able to carry more samples in parallel. By using disposable tips at the ends of the shafts of the tool, which can be ejected from the tool and replaced with new tips when required, the tips can function as single-use disposable items to prevent residue from one experiment contaminating a subsequent experiment.

At least some examples provide a tip ejector block for ejecting tips from tip-carrying shafts of a multi-channel laboratory tool, the tip ejector block comprising: a plurality of apertures for receiving the tip-carrying shafts of the multi-channel laboratory tool, where the plurality of apertures are spaced along a first axis at regular intervals of a predetermined spacing interval; and a front end surface comprising a plurality of contact surface portions, each contact surface portion surrounding a respective one of the apertures for contacting the tip on a corresponding one of the tip-carrying shafts to eject the tip when in use; in which: in at least one configuration of the tip ejector block: the apertures comprise a first subset of apertures and a second subset of apertures, where the first subset of the apertures are interleaved with the second subset of the apertures in an alternating pattern; and when the tip ejector block is moved along a second axis perpendicular to the first axis with the front end surface facing a direction of travel, the contact surface portions associated with each of the first subset of apertures would reach a given position along the second axis before the contact surface portions associated with each of the second subset of apertures reach the given position.

At least some examples provide a computer-readable storage medium storing a shape- representing data structure representing a shape of the tip ejector block as described above, for controlling an additive manufacturing machine to manufacture the tip ejector block by an additive manufacturing process. The storage medium may be a non-transitory storage medium. At least some examples provide a multi-channel laboratory tool comprising: a plurality of tip-carrying shafts for carrying tips ejectable from the tip-carrying shafts; the tip ejector block as described above; and an ejection mechanism to actuate movement of the tip ejector block along the tip-carrying shafts to eject the tips from the tip-carrying shafts.

At least some examples provide a multi-channel laboratory tool comprising: a plurality of tip-carrying shafts for carrying tips ejectable from the tip-carrying shafts, where the tip-carrying shafts are spaced at regular intervals of a predetermined spacing interval; and an ejection mechanism to eject the tips from the tip-carrying shafts; in which: in response to a first user- selected action, the ejection mechanism is configured to eject the tips from a first subset of the tip-carrying shafts; in response to a second user-selected action distinguishable by the user from the first user-selected action, the ejection mechanism is configured to eject the tips from a second subset of the tip-carrying shafts; and the first subset of the tip-carrying shafts are interleaved with the second subset of the tip-carrying shafts in an alternating pattern.

Further aspects, features and advantages of the present technique will be apparent from the following description of examples, which is to be read in conjunction with the accompanying drawings, in which:

Figure 1 shows an example of a multi-channel pipette;

Figure 2 shows a number of views of a tip ejector block for ejecting tips from tip-carrying shafts of a multi-channel laboratory tool, such as the pipette of Figure 1 ;

Figure 3 is a graph showing offset distances for a first subset of apertures and a second subset of apertures of the tip ejector block;

Figures 4A, 4B, 4C and 4D illustrate an example of use of the tip ejector block to control ejection of tips from the pipette so that a first subset of tips are ejected in response to a first user- controlled action and a second subset of tips interleaved with the first subset are ejected in response to a second user-controlled action;

Figures 5 to 7 show further views of the tip ejector block in one embodiment;

Figure 8 illustrates a profile of a front end surface of a second example of a tip ejector block in which there are three subsets of apertures with offset distances grouped into three different bands;

Figure 9 shows an example of a spring serving a biasing mechanism to resist displacement of a button or lever for controlling the tip ejection;

Figure 10 shows an example shape for forming the spring;

Figure 11 shows a number of alternative examples of implementing the biasing mechanism;

Figures 12 and 13 show examples of tip ejector blocks with adjustable offset distances for the respective apertures;

Figure 14 shows an example of a tip ejector block for use with an automated liquid handling laboratory tool; Figure 15 shows an example of a magnetic-bead-carrying tool with which the tip ejector block could be used; and

Figure 16 shows an example of controlling additive manufacture of the tip ejector block.

Multi-channel laboratory tools, such as a multi-channel pipette, are commonly in use within scientific research laboratories for handling experiments involving multiple channels of sample disposed in wells, tubes or other vessels. The sample could, for example, comprise chemical or biological material disposed in solution or disposed on a solid substrate such as beads. For such experiments, it is common to use a set up where the spacing between adjacent tubes or wells is a fixed distance which is standardised in the industry. For example, test tube racks and well plates with an inter-tube or inter-well spacing of 9 mm are commonly in use (although other spacings can also be provided). Hence, multi-channel pipettes or other similar laboratory tools may have shafts arranged along an axis at regular intervals of a fixed predetermined spacing interval designed to match the spacing interval of the particular lab rack or well plate for which that tool is designed. As 9 mm is one of the most common spacings, then this is a common spacing used between the respective shafts of a multi-channel pipette or other laboratory tool. If tube racks or well plates with a different spacing are to be used, this would require a different multi-channel laboratory tool to be used for that particular experiment, to account for the variation in the spacing between adjacent tubes or wells. Maintaining multiple different tools with different inter-shaft spacings increases expense for the laboratory.

Some multi-channel pipettes are available which have an adjustable spacing between adjacent shafts of the pipette, where a concertina mechanism or other mechanical arrangement is used to allow the shafts of the multi-channel laboratory tool to move apart or towards each other along a linear axis perpendicular to the axes of the shafts themselves, so as to adjust the tool for use with different tube or well spacings. However, such a mechanism tends to make the adjustable multi-channel pipette more bulky, increases complexity and hence a potential source of failure and increases the cost of such pipettes. Also, standard non-adjustable pipettes are so prevalent that for laboratories to replace their existing non-adjustable pipettes with new adjustable pipettes would require some expense which may not be considered justified.

In the examples below a tip ejector block is provided for ejecting tips from tip-carrying shafts of a multi-channel laboratory tool. The tip ejector block comprises a number of apertures for receiving the tip-carrying shafts of the multi-channel laboratory tool. The apertures are spaced along a first axis at regular intervals of a predetermined spacing interval. For example, the predetermined spacing interval could be 4.5 mm or 9 mm to match common spacings used for tube racks or well plates for example (e.g. 384 well plates use 4.5 mm spacing and 96 well plates use 9 mm spacing). Hence, in use the apertures can slide over the shafts of the multi-channel pipette or other similar laboratory tools already found in the laboratory. The block has a front end surface which has a number of contact surface portions, each contact surface portion surrounding a respective one of the apertures for contacting the tip on a corresponding one of the tip-carrying shafts to eject the tip when in use. For example, when in use the tip ejector block can slide down the shafts of the multi-channel laboratory tool with the shafts passing through the apertures, and then the front end surface may approach the disposable tips carried on the tip-carrying shafts, so that the respective contact surface portions of the front end surface touch the tips to push the tips off the shafts and eject them from the multi-channel laboratory tool.

The tip ejector block has at least one configuration in which: the apertures comprise a first subset of apertures and a second subset of apertures, where the first subset of the apertures are interleaved with the second subset of the apertures in an alternating pattern; and when the tip ejector block is moved along a second axis perpendicular to the first axis with the front end surface facing a direction of travel, the contact surface portions associated with each of the first subset of apertures would reach a given position along the second axis before the contact surface portions associated with each of the second subset of apertures reach the given position.

Hence, when the tip ejector block is moved along the second axis with the front end surface facing the direction of travel (similar to the motion that would be made when the tip ejector block is in use for ejecting tips from the multi-channel laboratory tool), the contact surface portions associated with the first subset of apertures will reach a given position along the second axis before the contact surface portions associated with each of the second subset of apertures. This means that, when in use the tips on a first subset of tip-carrying shafts would be ejected from the shafts earlier than the tips carried by a second subset of the tip-carrying shafts, so the ejector block can be used to adapt the pattern with which the tips are ejected from the block so that the user can control ejection of only a subset of the tips from the multi-channel laboratory tool while retaining other tips. As the first and second subsets of apertures are interleaved in an alternating pattern, this means that the corresponding tips ejected in stages also correspond to that alternating pattern. This can be particularly useful for adapting the multi-channel laboratory tool for use with tube racks or well plates of different layouts, arrangements or spacings. This avoids the need for a laboratory to buy a new tool to deal with a different arrangement of tube rack or well plate and may further allow for the transfer of material from one form factor to another (i.e. 4.5mm well spacing to 9mm well spacing). Also, unlike the adjustable multi-channel laboratory tools described above which require a complicated and expensive mechanical arrangement to adjust the position of the tip-carrying shafts, the tip ejector block may be cheap to manufacture and simple to retrofit onto existing tools to reduce the expense for laboratory operators.

The first axis described above is the axis along which the apertures are arranged. In use, this may correspond to the axis along which the shafts of the corresponding laboratory tool are arranged. The second axis is perpendicular to the first axis, and may correspond to the direction along which the tip ejector block moves to eject the tips when in use. In use, this second axis corresponds to the longitudinal axis of the shafts.

For each aperture of the tip ejector block, an offset distance may be defined for the corresponding contact surface portion surrounding that particular aperture. The offset distance for a given contact surface portion surrounding a given aperture may be defined as the distance, along the second axis, between a leading edge of the given contact surface portion and a leading edge of the front end surface as a whole. The leading edge of the front end surface as a whole may be the first part of the front end surface to reach a given position along the second axis when the tip ejector block is moved along the second axis with the front end surface facing the direction of travel. On the other hand, the leading edge of a given contact surface portion may be the first part of that given contact surface portion which reaches the given position along the second axis when the tip ejector block is moved along the second axis with the front end surface facing the direction of travel. Hence, the offset distance is effectively a measure of how long it will take the contact surface portion around a particular aperture to contact the corresponding tip when in use for tip ejection. When in use, a contact surface portion having a smaller offset distance would reach the corresponding tip sooner than a contact surface portion having a larger offset distance.

For at least one aperture of the first subset, the offset distance could be zero, since part of the contact surface portion around that aperture could be the leading edge of the front end surface. Alternatively, in some examples the leading edge of the front end surface may be at a position that does not act as any of the contact surface portions as it would not come in contact with the tips when in use, and in that case all of the apertures could have non-zero offset distances. The concept of the offset distance is useful to represent the sequence (or staging) with which the contact surface portions around different apertures will reach a given position along the second axis, which also represents the sequence/staging with which tips would be ejected from the multi-channel laboratory tool when the tip ejector block is in use.

Hence, in the at least one configuration of the tip ejector block, the offset distance for the contact surface portions associated with each of the second subset of apertures may be greater than the offset distance for the contact surface portions associated with each of the first subset of apertures.

In one example the apertures may comprise at least one aperture of the first subset which is disposed between two apertures of the second subset (either directly between the two apertures of the second subset, or indirectly between the two apertures of the second subset, so that there could be at least one further aperture between the aperture of the first subset and one or both of the neighbouring apertures of the second subset). Similarly, at least one aperture of the second subset may be disposed between two apertures of the first subset (either directly or indirectly). Hence, the alternating pattern of apertures may include at least one aperture of the first subset, followed by at least one aperture of the second subset, followed by at least one further aperture of the first subset, followed by at least one further aperture of the second subset. This alternating arrangement of apertures can be useful to adapt to tube racks or well plates with wider spacing (e.g. adapting from use for 384 well plate to use for a 96 well plate). In some examples the apertures may have a repeating pattern where the unit of repetition includes at least one aperture of the first subset and at least one aperture of the second subset, and there are at least two repetitions of that repeating pattern.

It is not essential for the first subset of apertures to be disposed with a regular spacing interval. For example, in some embodiments the arrangement of the first and second subset of apertures could be in groups so that, for example, the tip ejector block could have two apertures of the first subset, followed by two apertures of the second subset, followed by two apertures of the first subset, followed by two apertures of the second subset, and so on. For example, this could be useful for experiments when a multi-channel pipette designed for a very fine well spacing is being used with a much wider-spaced well plate or rack so that it is desirable for multiple adjacent channels of the tool to draw up fluid or expel fluid into the same larger well or tube. By using an ejector block with alternating blocks of first and second subsets of apertures the tips carried by shafts extending through the first subset of apertures could be released first and then the remaining tips used to provide fluid into one of these wider spaced well plates or racks.

It is not essential for the number of first subset of apertures to equal the number of second subset of apertures. Another example could have the apertures arranged in a pattern similar to 122122122... or 211211211... where every third aperture is an aperture of the first subset and remaining apertures are of the second subset (or vice versa), for example it is also not essential for the alternating pattern to be regular. In some examples a more irregular alternating pattern such as 11222122 or 21222122 could be used for bespoke experiments for specific purposes. For example, a laboratory could obtain a set of tip ejector blocks with different arrangements of the first and second subsets of apertures to handle different types of experiments, with much lower cost than a bespoke multi-channel pipette or similar tool for each experiment.

However, in one particular example it can be useful to provide a tip ejector block in which either: the first subset of apertures are spaced along the first axis at regular intervals of a wider spacing interval greater than the predetermined spacing interval, or the second subset of apertures are spaced along the first axis at regular intervals of the wider spacing interval. For example the wider spacing interval could be twice the predetermined spacing interval, four times the predetermined spacing interval, or some other integer multiple of the predetermined spacing interval. This would allow the user to control a first stage of tip ejection to eject tips from the shafts of the tool that correspond to the first subset of apertures, followed by a second stage of tip ejection from the shafts that correspond to the second subset of apertures. Either the first subset of tips or the second subset of tips may be positioned at spacings N times the nominal spacing of the multi-channel laboratory tool, which can be useful for dealing with tube racks or well plates of different regular spacings. It may be a matter of design choice whether the apertures which should be positioned at regular intervals are the first subset of apertures or the second subset of apertures, depending on the particular choice of the design or of the tip ejector block. In general, the contact surface portions of the front end surface may be shaped so that the contact surface portions around the first subset of apertures reach the tips first and then subsequently the contact surface portions around the second subset of apertures reach the tips, when in use, to control a phased ejection of different subsets of tips. One way of controlling this may be to provide the front end surface with a number of plateau portions and floor portions between the plateau portions, where the contact surface portions for the first subset of apertures comprise the plateau portions and the contact surface portions for the second subset of apertures comprise the floor portions. Hence, by forming plateaus and valleys in the front end surface this can provide the desired pattern of alternation of the first and second subset of apertures, by controlling the positions of the plateau portions and floor portions accordingly.

In some implementations all of the apertures of the tip ejector block could be considered to be part of either the first subset or the second subset.

However, for other examples a further third subset of apertures may also be provided in at least one configuration of the tip ejector block, where when the tip ejector block is moved along the second axis with a front end surface facing the direction of travel, the contact surface portions associated with each of the second subset of apertures would reach the given position along the second axis before the contact surface portions associated with each of the third subset of apertures reach the given position. Hence, in some cases the apertures could be divided into at least three subsets, so that when the block is in use and the user activates the ejection mechanism of the multi-channel laboratory tool, the first subset of tips disposed on shafts extending through the first subset of apertures will be ejected first, followed by the tips on a subset of shafts extending through the second subset of apertures, and finally the tips on a subset of shafts extending through the third subset of apertures. By providing staged release of tips in this way then this can provide further control over lab experiments. Optionally, further subsets of apertures could also be provided (e.g. a fourth subset, fifth subset, etc.).

In one example, the tip ejector block may be a rigid solid block of material without moving parts or a mechanical mechanism.

The given position reached along the second axis is described above may be any arbitrary position along the second axis. Due to the shape of the front end surface, when the tip ejector block is moved along the second axis with the front end surface facing the direction of travel, regardless of what particular position is chosen as the given position along the second axis, the contact surface portions associated with the first subset of apertures may reach that given position before the contact surface portions associated with the second subset of apertures (and if provided then the third subset of apertures may have the contact surface portions reaching that given position after the contact surface portions of the second subset of apertures). The same principle can be extended to fourth or fifth subsets of apertures or further if desired.

Hence, it will be appreciated that the definition of which contact surface portions reach the given position first does not depend on defining the given position as being at any specific position along the second axis, but rather the given position can refer to any arbitrary position selected along the second axis. In practice, in use the given position of interest may be the position at which the top of the tips sit when they are held on the shafts of the multi-channel laboratory tool. However, the same ejector block could be used with laboratory tools which use tips of different lengths, so the exact position of the top of the tips may vary, so the exact definition of the point where the block contacts the tips when in use is not important for defining the shape of the tip ejector block.

The tip ejector block may, in use, be affixed to the laboratory tool in different ways. The tip ejector block could include attachment members for fixing to the laboratory tool. For example, the tip ejector block could be clipped onto, or fitted into a slot of, an ejection carriage or other moving part which slides along the shafts to bring the ejector block into contact with the tips. Many designs of multi-channel laboratory tool already have a tip ejector block which implements a fixed offset distance for each of the apertures so that all of the tips are ejected at once, and such a standard ejector block could be replaced or modified with a tip ejector block as described in this application so as to convert the existing tool into a tool which is capable of ejecting subsets of tips separately.

In some implementations all of the apertures of the first subset may have contact surface portions with identical offset distances, and similarly all of the apertures of the second subset may have contact surface portions with identical offset distances different to the offset distances for the first subset of apertures.

However, this is not essential. In some examples the tip ejector block may have a profile of the front end surface so that the offset distances may vary among the apertures of the first subset. This means that, when the tip ejector block is moved along the second axis with the front end surface facing a direction of travel, the contact surface portions associated with at least two apertures of the first subset may reach the given position along the second axis at different times. Similarly, for the apertures of the second subset the contact surface portions may have different offset distances, and so there may be contact surface portions associated with at least two apertures of the second subset that may reach the given position along the second axis at different times.

For example, the offset distances for the respective contact surface portions associated with apertures of the first subset may be within a first band of offset distances, but need not be identical to each other, while the offset distances for the contact surface portions associated with the apertures of the second subset may be within a second band of offset distances different from the first band. It can be useful to provide slightly differing offset distances for different apertures of the first subset or for different apertures of the second subset, because this will avoid the ejection mechanism of the multi-channel laboratory tool touching many tips all at once which would tend to increase the resistance to ejection and require the user to apply greater force to eject the tips. By providing some variation of the offset distances for different apertures within the first subset or within the second subset, this can spread out the force applied by the user so that although each of the apertures of the first subsetwill have their corresponding tips released before any other tip is released from a shaft passing through one of the apertures of the second subset, the release of the first subset of tips will be spread out over time (but imperceptible for the user) to reduce the effort in releasing the tips. Nevertheless, the maximum difference in offset distance between any two apertures of the first subset may be less than the minimum difference in offset distance between any one aperture of the first subset and any one aperture of the second subset, so as to preserve the user-controllable selection of whether the first subset or the second subset should have their tips ejected.

As mentioned above, the definition of the first and second subset of apertures may be provided in at least one configuration of the tip ejector block. In some implementations this may be the only configuration of the tip ejector block supported, so there is no ability to adjust the pattern in which first and second subsets of apertures (and further subsets if provided) are arranged. In this case the block may simply be a fixed solid object without any moveable parts. If a different pattern is desired then the entire tip ejector block could be replaced with an alternative block with a different pattern.

However, in another example at least one of the apertures could have a contact surface portion with an adjustable offset distance. That is, the tip ejector block could have two or more different configurations where one configuration could have at least one aperture with a different offset distance compared to the offset distance provided for that same aperture in another configuration. For example, this could be achieved by providing certain slideable portions of material which can be moved in and out to change the position of the leading edge of the contact surface portion that surrounds a given aperture. For example extra pieces of material could slide linearly into position for one configuration and then be removed for another configuration. Another option may be that there may be some additional plateau portions which can be pivoted into position in a rotating action and clipped into place in one configuration, but in another configuration these portions could be removed and withdrawn to a position where the extra material will not interact with the tips when in use. This can allow the same tip ejector block to handle experiments with different requirements for staging of tip ejection from the respective shafts of the multi channel laboratory tool.

The tip ejector may be retrofittable to an existing multi-channel laboratory tool. This can greatly reduce the cost of implementing tools capable of interfacing with different sizes of well plate or rack, as it prevents the need to replace the entire tool and instead only the tip ejector block may be replaced or fitted. The tip ejector block can be an inexpensive part which can be manufactured cheaply, compared to the more complex laboratory tool itself. The tip ejector block may be sold and marketed as a stand alone product, so does not need to be sold together with the corresponding laboratory tool. Hence, the tip ejector block alone may correspond to an industrially applicable item. It is not essential for the multi-channel laboratory tool having the tip- carrying shafts, or any associated tip ejection mechanism to be part of the claimed tip ejector block.

The tip ejector block can be manufactured through any known manufacturing technique for manufacturing a component with a desired shape. For example the block could be formed by injection moulding, casting, etc. However, one way of making the tip ejector block can be to use an additive manufacturing process, where instead of forming the object by removing material from a larger block of material as in subtractive manufacturing processes, the block is made by laying down successive layers of material one by one and processing each layer to form the shape of the block. For example the additive manufacturing process may comprise 3D printing, powder bed fusion, directed energy deposition, selective laser melting, or any other examples of additive manufacturing process. An advantage of using additive manufacturing is that intricate shapes can be made to precise degrees of tolerance which may not be possible using conventional subtractive manufacturing processes.

As it is possible for the tip ejector block to be made by additive manufacturing, and such additive manufacturing processes may typically operate under computer control, where the shape of the block to be manufactured is represented by an electronic design-representing data structure that is used to control the additive manufacturing machine to form the block with the desired shape, then it is not essential for the tip ejector block to be sold and marketed as a physical object. Although some parties may choose to provide the block as a physical object, another way of distributing the block may be to provide a shape-representing structure which represents the shape of the tip ejector block, so that the recipient can then use that data structure to control their additive manufacturing machine to manufacture the tip ejector block at the recipient’s side. Hence, in some cases the item of industrial application may be a shape-representing data structure as described above, rather than the block itself. The shape representing data structure may be stored on a computer-readable storage medium, which could be a non-transitory storage medium. For example, the shape-representing data structure could be a computer-aided design (CAD) file which represents the 3D shape of the block including the design of the front end surface. Alternatively, the shape-representing data structure can be a slice-by-slice data representation where each layer of the block is represented by a separate portion of the data structure, ready for controlling the additive manufacturing machine to control laying down, melting or patterning the material for that particular layer. It will be appreciated that the shape- representing data structure could be represented in different formats. In general by using such a data structure to define the shape of the tip ejector block having the apertures of the first and second subsets with contact surface portions described as above, this can allow the recipient of such a data structure to use their additive manufacturing machine to make the block and then use it in the lab.

As described above, the tip ejector block could be retro-fitted to existing multi-channel laboratory tools. However, in other examples the tip ejector block could be part of a standalone multi channel laboratory tool and supplied along with the tool itself. Alternatively, a set of one or more replaceable tip ejector blocks could be provided along with a multi-channel laboratory tool so that the user can select which particular tip ejector block should be fitted for a given experiment. Hence, although useful for retrofitting to existing tools, the tip ejector block may also have use with newly supplied multi-channel laboratory tool themselves and may be marked along with the tool in some cases, either as an integral non-removable component or as a replaceable component which can be replaced with other tip ejector blocks. Even in a laboratory tool which does not allow replacement of its tip ejector block, the techniques discussed above could still be useful to provide certain bespoke laboratory tools which are suitable for providing tip ejection in certain controlled patterns.

Hence, in some examples a multi-channel laboratory tool may have a number of tip carrying shafts for carrying tips that are ejectable from the shafts, and a tip ejector block as described above. An ejection mechanism may be provided to actuate movement of the tip ejector block along the tip-carrying shafts to eject the tips from the tip-carrying shafts. In the example where the entire laboratory tool is provided, then the first axis of the tip ejector block may correspond to the axis along which the tip-carrying shafts of the laboratory tool are arranged, and the second axis of the tip ejector block may correspond to an axis parallel to the longitudinal axis of the tip-carrying shafts.

Hence, when the laboratory tool is in use then, in response to a first user-selected action, the ejection mechanism may move the tip ejector block along the tip-carrying shaft parallel to the second axis, and then in response to a second user-selected action distinguishable by the user from the first user-selected action, the ejection mechanism may move the tip ejector block further along the tip-carrying shafts beyond the position reached in response to the first user-selected action. The position reached after the first user-selected action may correspond to a position at which, when in use, the contact surface portions around the first subset of apertures reach the position of the tips to eject the tips from the shafts associated with that first subset of apertures, while the second user-selected action may then move the tip ejector block further so that the contact surface portions around the apertures of the second subset also reach the corresponding tips (when in use) to eject those tips.

The first and second user-selected actions may be any two actions which can be distinguished by the user. For example, in bespoke laboratory tools designed from the outset to use a tip ejector block with first and second subset of apertures as described above, the first and second user controlled actions could be triggered by separate buttons or separate electronic commands provided to control the ejection of first and second subsets of tips respectively.

However, in other examples the first and second user-selected actions may be controlled by mechanical displacement of a single button or lever. Some existing laboratory tools may already have a button or lever for controlling tip ejection, but may not originally be designed to support the user selecting first and second subsets of tips for ejection separately. When the tip ejector block is retrofitted to such a tool, then the same ejection button may still be used by the user to control both the first and second stages of tip ejection. The user may, for the first user- selected action, mechanically displace the button or lever from a starting position to a first control position, and then for the second user-selected action further mechanically displace the same button or lever beyond the first control position to reach a second control position. Hence, the user can feel that with a smaller displacement of the button or lever the first subset of tips will be ejected but with a larger displacement then both the first and second subsets of tips are ejected. This avoids the need to provide any separate user-controlled mechanism for ejecting the second subset of tips, and means that the techniques discussed above can be retrofitted to an existing tool designed for ejecting all the tips at once.

It can be useful to provide a biasing mechanism to resist displacement of the button or lever between the first control position and the second control position, to assist the user with distinguishing the first control position and the second control position. By providing additional resistance to the user displacing the button, this makes it simpler for the user to intentionally select the displacement of the button or lever to the first control position so as to only eject the first subset of tips, without accidentally pushing the button or lever so far that it reaches the second control position. This biasing mechanism could be integral in the multi-channel laboratory tool in a design where the tool is designed to have the ejector block described above from the outset, or could be retrofittable to an existing laboratory tool to adapt that tool to use the tip ejector block of the current technique.

The biasing mechanism could be implemented in different ways. In one example the biasing mechanism could be a spring. The spring could be made of metal or plastic or any other resilient material. The spring could be wound around the button or lever actuated by the user, or provided at another component of the tool that moves when the ejector mechanism is actuated. The spring could be an internal spring which is hidden from view when the tool is in use, or could be an external spring which is visible when in use. An external spring may be simpler to retrofit on to existing designs, although in some cases the button may be removable and the spring could be hidden inside the button even when retrofitting.

In another example, the biasing mechanism could use magnets to provide the resistance to displacement of the button or level between the first and second control positions. For example, opposed magnets could be positioned to provide a separation force which increases as the button or lever is displaced from the first control position to the second control position. Alternatively attracting magnets could be positioned to provide an attraction force which decreases as the button or level is displaced from the first control position to the second control position. Either way, the user may find it increasingly difficult to move the level from the first control position to the second control position so that there is some additional force needed to reach the second control position, which makes it less likely that the user accidentally ejects the second subset of tips when only the first subset of tips was intended to be ejected. Regardless of whether the magnets are opposed or attracting, the magnets could be positioned at various points of a multi channel laboratory tool, for example on the button or lever used for controlling ejection itself, or on another part of the tool where moving parts move relative to each other when the ejection mechanism is in use (for example one of the magnets could be disposed on a static body of the tool and another magnet disposed on a moving part of the ejection mechanism, not necessarily on the button/lever itself, which moves when the ejection mechanism is triggered).

In examples where there is a third subset of apertures as discussed earlier, the biasing mechanism may further resist displacement of the button/lever between the second control position and a third control position corresponding to the position at which the tips associated with the third subset of apertures are released. Similarly, if there is a fourth or further subset of apertures, there may be resistance provided by the biasing mechanism to resist the user moving the lever/button between successive control positions corresponding to release of successive subsets of apertures.

In one example, the techniques discussed above can be applied to a manual tool which is portable by a user. Such manual multi-channel laboratory tools such as multi-channel pipettes are commonly used for workbench experiments within life sciences laboratories and the techniques discussed above can provide a relatively cost effective way of adapting such tools for new uses. However, the techniques can also be applied to multi-channel laboratory tools which have an automated control mechanism for controlling ejection of the tips from the tip-carrying shafts. For example some automated devices may provide two-dimensional arrays of shafts which can carry tips providing fluid or other material and which can, under automated control, release their contents into an array of tubes, wells or vessels and eject the tips when needed. Such automated devices can also be fitted with tip ejector blocks with a front end surface having contact surface portions of different heights for different subsets of apertures. Hence, the tip ejector block can be used to adapt the pattern with which the tips are released when the automated ejection mechanism is activated.

The biasing mechanism can be particularly useful for a manual tool, to allow the user to distinguish the positions at which the tips corresponding to respective subsets of apertures are released. However, the biasing mechanism is not essential, and in other examples it may be possible for the user to distinguish the control positions without the biasing mechanism. Nevertheless, the biasing mechanism can help to make the tool more user-friendly.

On the other hand, for automated tools, the biasing mechanism described above may not be essential as for some designs of automated tool, the automated control mechanism may be configured to move the tip ejector block by set distances to reach the first/second/further control positions, so that there is no need for additional biasing to be provided. Alternatively, for other designs of automated tool, the biasing mechanism may still be useful. The techniques discussed above can be particularly useful when applied to a multi channel pipette where the tips carried by the tip-carrying shafts are fluid-carrying tips which can be used to carry liquid sample between one container and another. Such a multi-channel pipette may, in addition to the ejection mechanism, also include a fluid-aspirating mechanism (e.g. a piston driven suction/release mechanism) for drawing fluid into the tips and expelling fluid from the tips.

However, the techniques can also be used for other types of multi-channel laboratory tool which have tip-carrying shafts for use with disposable tips. For example, a magnetic-bead carrying tool can be provided where each tip-carrying shaft comprises a magnetic rod for attracting magnetic beads onto the tips carried by the tip-carrying shafts. The magnetic rods may be retractable so that the rods can be moved up or down to control attraction of the beads onto the tips or release the beads from the tips. For similar reasons to the pipettes, it can be desirable to use single-use disposable tips on such a magnetic-bead-carrying tool to prevent contamination of future experiments based on residue from earlier experiments. Experiments involving magnetic beads can be useful for many life science laboratories for conducting research involving manipulation of biological material such as cells, nucleic acids, proteins or micro-organisms. Similar to the pipette example, the tip ejector block described above can be useful for adapting the magnetic-bead-carrying tool so that some shafts of the tool may drop their tips while leaving other shafts carrying their tips at positions interleaved with the positions of the shafts which dropped their tips.

In another example, a multi-channel laboratory tool may have a number of tip-carrying shafts for carrying tips ejectable from the shafts, where the tip-carrying shafts are spaced at regular intervals of the predetermined spacing interval. An ejection mechanism may eject the tips from the tip-carrying shafts when selected by the user. In response to a first user-selected action the ejection mechanism may eject the tips from a first subset of tip-carrying shafts. In response to a second user-selected action which is distinguishable by the user from the first user-selected action, the ejection mechanism may eject the tips from a second subset of the tip-carrying shafts. The first and second subsets of tip-carrying shafts may be interleaved in an alternating pattern. This approach provides a tool capable of interacting with different arrangements of tube racks or well places. For example this can be useful for transferring material from a 96 well plate having a 9 mm well to well spacing and a 384 well plate having a 4.5 mm well to well spacing.

Figure 1 schematically illustrates an example of a multi-channel pipette, which is an example of a multi-channel laboratory tool. The pipette 2 has a handle 4 and a pipette body 6. The dimensions shown in Figure 1 are not shown to scale, as for example the length of the handle 4 is shown shorter than it would be in practice (the size of the body has been exaggerated compared to the handle to allow better visibility of the components within the pipette body 6). In practice, the length of the handle 4 would be greater than shown in Figure 1. Similarly, other dimensions shown in Figure 1 may not be to scale. Extending from the pipette body 6 are a number of tip-carrying shafts 8 which are positioned along a first axis (labelled the x axis in Figure 1) with a regular spacing interval V between adjacent shafts 8. When in use, each shaft 8 is for carrying a corresponding disposable tip 10. The tips 10 are for holding liquid sample when carrying out laboratory experiments. The tips 10 are not themselves part of the pipette 2 but would be provided separately as disposable single-use items, while the pipette 2 would be re-used across different experiments.

The pipette has a fluid aspirating mechanism for drawing fluid into the tips 10 through a hole 12 at the bottom of each tip 10, and expelling fluid from the tips 10. The shafts 8 are hollow and open at the lower end. The upper end of each shaft 8 is connected to a piston chamber 14 within which a piston 16 is disposed. The piston 16 can be driven up and down by the user moving a fluid aspiration control plunger 18 which extends down the handle 4. In this example, the upper portion of the piston chambers 14 and pistons 16 are hidden from view within the pipette body 6, as shown by the dotted lines in Figure 1. In this example, the lower portion of the piston chambers 14 extend outside the pipette body 6 and so is visible (as shown in the part of the piston chambers 14 indicated with solid lines). In other examples, the piston chambers 14 could be fully disposed within the pipette body 6 and so may not be visible to the user at all, and in this case the shafts 8 may be the only portion protruding out of the body 6 to be visible to the user,.

When in use, empty tips 10 are placed over the shafts 8 (e.g. by placing the tips 10 in tubes or wells with their upper end facing the pipette, and then moving the pipette down onto the tips to insert the shafts 8 into the tips 10). When the user wishes to draw fluid into the tips 10, prior to inserting the tips 10 into the fluid, the user prepares for drawing up fluid by pushing in the fluid aspiration control plunger 18 to drive the piston 16 down towards the ends of the piston chambers 14. Then, having inserted the ends of the tips 10 into fluid containing wells or tubes, the user pulls up the fluid aspiration control plunger 18 to raise the piston head 16 up towards the top of the piston chambers. The resulting drop in air pressure within the tips 10 and shafts 8 creates suction which causes fluid to be drawn from the wells or tubes into the tips 10. The pipette 2 can then be removed from the tubes or wells, and the surface tension of the fluid in the tips 10, combined with the air pressure of the external air pushing on the bottom surface of the fluid, prevents gravity pulling the fluid out of the tubes, so that the fluid is retained despite the fact that the ends 12 of the tips 10 are open.

The user can then move the pipette over to a different set of wells or tubes or other laboratory vessels, and expel the fluid from the tubes by pushing the fluid aspiration control plunger 18 down again to cause the piston 16 to move back down the piston chambers 14. This increases the pressure of the air trapped between the piston head 16 and the upper surface of the fluid in the tips 10, compared to the external air pressure acting on the bottom surface of the fluid nearest the tip ends 12, causing the fluid to be expelled from the tips. The fluid aspiration mechanism shown in the example of Figure 1 is just one example and other pipettes can use a different mechanism. Figure 1 shows an example of an air displacement pipette where the piston head 16 is not in direct contact with the fluid to be expelled, and instead the piston 16 acts on an intervening pocket of air whose pressure can be increased to expel the fluid. However, it is also possible to provide positive-displacement pipettes where the piston head 16 pushes directly against the fluid itself.

The pipette 2 also has a tip ejection mechanism for ejecting the tips 10 from the pipette. An ejection carriage 20 is disposed about the shafts 8 so that the shafts pass through the ejection carriage 20. The ejection carriage 20 is able to slide up and down the shafts 8. The shafts 8 extend parallel to a second axis (labelled the y axis in Figure 1) and the carriage 20 moves parallel to that second axis. The ejection carriage 20 carries a tip ejector block (also known as an ejection control block) 22 which has a front end surface 24 for engaging with the upper ends of the tips 10 to push the tips 10 off the ends of the shaft 8 when the ejector carriage 20 is moved down over the shafts 8. In this example the ejector carriage 20 is connected by connecting arms 26 to an ejection control handle 28 and the upper end of the ejection control handle forms an ejection control button 30 which extends out the top end of the handle 4. In other examples, the ejection carriage 20 could be actuated by the user moving a lever, instead of a button.

Hence, the user can push the ejection control button 30 down to cause the ejection carriage 20 to move down so that the tip ejector block 22 slides over or alongside the shafts and ejects the tips 10 from the pipette 2. When the user releases the ejection control button 30, a return spring (not shown in Figure 1) may cause the ejection carriage 20 to move back to its resting position ready for a future ejection of tips.

It will be appreciated that the ejection control mechanism shown in Figure 1 is just one example. It is not essential for the ejection control mechanism to be controlled by a mechanical lever or button. In other examples the ejection control mechanism could be actuated by the user pressing a button or touch screen which causes an electronic command to be issued to cause the ejection mechanism to mechanically push the tips 10 off the ends of the shafts 8.

The tip ejector block 22 may be fixed to the ejector carriage 20 in different ways. For example, the tip ejector block 22 could have integral clips which clip over portions of the ejector carriage 20 (e.g. see the clips 74 shown in Figure 5 described further below). Alternatively, the ejector carriage 20 could comprise an outer rim with a central aperture or slot, and the tip ejector block 22 could sit within the aperture or slot of the ejector carriage 20. Also, in some implementations the tip ejector block 22 and the carriage 20 could be formed integrally as one piece, so it is not essential for two separate components to be provided. However, providing the tip ejector block 22 as a separate component to the ejector carriage 20 can be useful because it allows the tip ejector block 22 to be replaced more easily, to support different arrangements of staged tip ejection as discussed below.

Figure 1 shows an example of a pipette with eight channels (that is, there are eight shafts 8 which can hold a maximum of eight tips 10 at a time). However, other examples may have a larger or smaller number of channels, for example 4 or 12 (or blocks of 96 in automated systems as discussed with respect to Figure 14 below).

In a typical multi-channel pipette 2, the tip ejector block 22 is designed so that its front end surface 24 will, when sliding down the shafts 8 under control of the ejector control mechanism, contact the tips on each of the shafts 8 at substantially the same time so as to eject all of the tips from the pipette. For many experiments this may be sufficient. The pipette 2 may generally be designed for use with a well plate or tube rack with wells or tubes at certain standardised spacings, and so the regular spacing interval V between the shafts 8 may be chosen to match the spacing of the corresponding plate or rack. For example, it is common to use tube racks with a tube-to- tube centre spacing of 9 mm, or well plates with well-to-well centre spacings of 9 mm or 4.5 mm (although other spacings are also possible). Hence, a pipette can be chosen with the regular spacing interval V between the shafts 8 matching the spacing of the rack or plate being used.

However, sometimes a lab scientist may wish to transfer fluid between racks or plates with different spacings. For example, fluid may need to be transferred between a 96 well plate with a 9mm well to well spacing and a 384 well plate with a 4.5mm well to well spacing. Also, some tube racks may have a less conventional inter-tube spacing, for example because the rack has other features provided between adjacent tube apertures of the rack (or the tubes themselves are too large to allow for standardized spacing). For example, a tube rack could be provided with magnets disposed around the apertures for receiving tubes, so that the magnets can be used to selectively apply magnetic fields to the contents of the tubes, which can be useful for experiments involving magnetic beads. Also, some tube racks may have heating mechanisms or other devices disposed between the tubes, which may increase the spacing between the tubes. Another alternative is that tubes are too large to allow for the standard 9mm spacing. Hence, some racks could have tubes spaced at double the conventional 9 mm spacing, for example so that the spacing becomes 18 mm. A conventional multi-channel pipette 2 as shown in Figure 1 would not cope well with such differences of spacing because the fluid aspiration mechanism and the ejection mechanism process the tips 10 on all of the shafts 8 at once. Some multi-channel pipettes 2 are known where it is possible to adjust the regular spacing interval V between the shafts 8, but these require a complicated mechanical mechanism more prone to failure to allow the inter-shaft spacing to be varied and would in any case require laboratories to replace all their existing pipettes with new pipettes.

In the examples described below, the tip ejector block 22 may be provided with a front end surface 24 which, in at least one configuration of the tip ejector block 22, is profiled so as to vary the point at which the front surface of the tip ejector block 22 contacts the tips 10 on the different shafts 8 of the pipette, so as to divide the tips 10 into different subsets which can be released at different stages of a staged ejection process. This recognises that on many existing pipettes, the tip ejector block 22 is removable and can be replaced with a new tip ejector block having a different profile of the front end surface 24, so that an existing pipette can be adapted for different well or tube spacings by fitting a different tip ejector block 22. For example a new tip ejector block may be clipped to the ejector carriage 20 or may sit within a slot in the ejector carriage as described earlier. Hence, this can provide a relatively inexpensive way of converting an existing pipette to adapt it to different spacings, avoiding the need to purchase a new pipette. Nevertheless, it is also possible for standalone pipettes with integrated tip ejector blocks 22 to be provided with a tip ejector block having the front end surface profiled as described below, so this technique could also be used by pipette manufacturers when manufacturing complete pipette devices. Hence, the technique can be provided either as a retrofit to an existing pipette or as part of the pipette itself.

Figure 2 shows three views of the tip ejector block 22. Part A of Figure 2 shows a view of a top surface of the tip ejector block 22 when viewed along the Y axis in the direction marked A in Figure 1 , that is, when viewed from the top end of the pipette in a direction extending from the handle end towards the shaft end of the pipette. As shown in the top view of part A, the tip ejector block 22 comprises a solid block of material 40 which comprises a number of apertures 42 which are spaced at regular intervals V to match the regular spacing between the shafts 8 of the pipette 2 for which the block is designed. In this example, the tip ejector block 22 is a solid block of material with no moving parts. For example, the block could be made of metal, plastic or any other solid material.

Part B of Figure 2 shows a view of the front end surface 24 of the tip ejector block 22, when viewed along the Y axis in a direction marked B in Figure 1 (that is, the direction extending from the shaft end of the pipette up towards the handle end). Around each aperture 42 is provided a contact surface portion 46, which is the part of the front end surface which will contact the top of the corresponding tip 10 when in use. The contact surface portions 36 are shown shaded in view B of Figure 2. The portions shown unshaded in part B of Figure 2 represent parts of the front end surface 24 which do not act as the contact surface portion 46 (e.g. because they are too far away from the aperture 42 to contact any part of the tips 10 when in use). In some examples, the unshaded regions between apertures may be omitted, if the inter-aperture spacing V is small enough that the contact surface portion for one aperture directly abuts the contact surface portion for another aperture.

Different subsets of apertures 42 have their contact surface portions disposed at different heights along the Y axis, as shown in the view shown in Figure C of Figure 2, which shows the surface profile of the front end surface 24 when viewed along the Z axis extending into the page in the view shown in Figure 1. The view shown in part C of Figure 2 shows the profile of an internal region of the front end surface, which comprises a number of plateaus 50 and valleys 52. Note that around the edge of the tip ejector block 22 there may be an outer rim portion which may hide the plateaus and valleys from the view of the user when in use. Hence, it is not necessary that the profile shown in part C of Figure 2 is visible externally. As shown in part C, a first subset of the apertures (in this example the first subset comprises apertures A1 , A3, A5, A7) have their contact surface portions formed on the upper surface of plateau portions 50 of the front end surface, while a second subset of apertures (in this example apertures A2, A4, A6, A8) have their contact surface portions 46 formed at the base of valley portions 52 which are positioned between the plateau portions 50. This means that when the tip ejector block 22 is moved along the second axis (Y axis) along the shafts 8 of the pipette when in use, with the front end surface 24 pointing towards the direction of travel, the contact surfaces 46 on the tops of the plateau portions 50 will reach the end of the tips 10 before the contact surface portions 46 at the base of the valley portions 52, and so the tips 10 on the shafts 8 corresponding to the first subset of apertures A1, A3, A5, A7 would be ejected first, and then the ejection control button 30 would need to be pushed further to eject the remaining second subset of tips from the shafts by pushing the tip ejector block 22 further along the second axis until the contact surface portions 46 at the bottom of the valleys 42 touch the top ends of the corresponding tips 10 disposed on the shafts which extend through the second subset of apertures A2, A4, A6, A8. This allows the user to select which tips are released when, which can be useful for allowing the pipette to be used with well plates or tube racks of different spacing or other user needs.

Figure 3 is a graph showing an offset distance associated with each aperture A1 to A8 of the tip ejector blocks 22. Here, the offset distance is defined as the distance between the leading edge of the contact surface portion 46 associated with that aperture and the leading edge 60 of the front end surface as a whole. The leading edge 60 of the front end surface as a whole is the part of the front end surface 24 which will reach a given point on the Y axis first when the tip ejector block moves along the Y axis with the front end surface 24 facing the direction of travel. In some examples, the tip ejector block 22 could have an outer rim which is positioned wide enough out from the apertures that it will not touch any of the tips 10 when in use, but which extends beyond the leading edge of any of the contact surface portions 46, so that the leading edge of the front end surface is not a part which engages with any of the tips 10. In this case, all of the apertures may be associated with a non-zero offset distance. However, in the particular example shown in Figures 2 and 3, the offset distance 01, 07 associated with apertures A1 and A7 is zero, as for this particular example the leading edge of the front end surface as a whole corresponds to the leading edge of the plateau portions 50 associated with apertures A1 and A7. For any apertures which have a contact surface portion 46 which extends further back from the leading edge 60 of the front end surface as a whole, the offset distance will be non-zero.

As shown in Figure 3, in this example the apertures are divided into a first set of apertures A1 , A3, A5, A7 which have their offset distances 01 , 03, 05, 07 within a first band 62 of offset distances, and a second subset of apertures A2, A4, A6, A8 which have their offset distances 02, 04, 06, 08 within a second band 64 of offset distances. All of the second subset of apertures have their offset distances greater than any one offset distance associated with the apertures of the first subset. Also, the minimum difference between the offset distance of any one of the first subset of apertures and the offset distance of any one of the second subset of apertures is greater than the maximum difference between any two apertures of the first subset or the maximum difference between any two apertures of the second subset. This means that there are two clearly differentiated subsets of apertures, which means that the corresponding tips and be ejected in corresponding clearly differentiated subsets.

As shown in Figure 3, it is not essential for all of the apertures in the first subset to be associated with contact surface portions 46 with identical offset distances. Similarly, the apertures of the second subset also do not need to all have the same offset distance for their contact surface portions 46. In fact, it can be useful to have some variation in the offset distances for the apertures within the same subset, so that when the user wishes to eject the tips, the contact surface portions reach the tips associated with apertures of the same subset at slightly different times, which helps to spread out the ejection force so that less effort is required to release the tips on the part of the user driving the ejection control lever 30. In contrast, if all of the first subset of tips had identical offset distances then the force applied by the user would be divided among a greater number of tips making it harder work to release the tips. Nevertheless, any variation between the offset distances for apertures within the same subset is optional, but if present the variation between offset distances for apertures in the same subset is less than the difference between the offset distance of an aperture in the first subset and the offset distance of an aperture in the second subset. This means that while the user can perceive a clear difference between the timing at which the first subset of apertures is released compared to the second subset, the differences between offset distances within apertures of the same subset are small enough that the user cannot perceive any appreciable difference in the timings at which the tips are released for that subset.

In this example, the apertures of the first subset are selected to be apertures A1 , A3, A5, A7 which are spaced along the first axis (X axis) at regular intervals of a wider spacing interval greater than the predetermined spacing interval V between the apertures 42. In this example the wider spacing interval is 2V, so that the first subset of apertures are spaced at twice the spacing of the apertures as a whole, and every other aperture is a member of the first subset. That is, the first subset of apertures are spaced at twice the spacing of the apertures as a whole, and every other aperture is a member of the second subset (so the second subset of apertures are also spaced apart at intervals of 2V).

Figures 4A to 4D show one example of use of the pipette 2 with the tip ejector block 22 as described above. The tip ejector block 22 is not shown in Figures 4A to 4D for conciseness, and instead these Figures simply show the effect of the control block on the release of the tips 10 from the pipette 2. Again, the diagrams are not drawn to scale.

As shown in Figure 4A, initially the pipette 2 is inserted onto the tips 10 which are held within a rack with a certain spacing V between adjacent tubes. As shown in Figure 4B, when the ejector control button 30 is depressed to a first control position then the first subset of tips which are on the shafts 8 extending through the first subset of apertures A1 , A3, A5, A7 of the tip ejector block 22 are ejected (e.g. allowing those tips to fall back into the tubes from which they were initially collected). This corresponds to a first phase/stage of tip ejection, leaving tips remaining on the shafts extending through the second subset of apertures A2, A4, A6, A8. As shown in Figure 4C, the remaining tips on the pipette can then be used to draw up fluid from a well plate or tube rack with twice the well/tube spacing (2V). As shown in Figure 4D, when the user wishes to release the second subset of tips, then the user further depresses the ejector control button 30 to a second control position and then this causes the contact surface portions 46 around the apertures 42 of the second subset to contact their respective tips and eject the tips. Hence, it is possible to use a pipette designed for racks/wells with a spacing of V to draw up / eject fluid in a rack/well with spacing 2V, without replacing the entire pipette 2.

It will be appreciated that Figures 4A to 4D just show one possible use of the pipette with the tip ejector block 22 shown above, but lab scientists may find many other uses. For example, another mode of use could be that, while tips 10 are held on all of the shafts 8 as shown in Figure 4A, fluid is drawn into all of the tips 10, before then ejecting the first subset of tips 10 into a first tube rack with fluid contained in the tips. The user could then move the pipette (with only the second subset of tips 10 remaining) above second a tube rack or well plate with spacing 2V and expel the fluid from the second subset of tips into respective tubes or wells of the second tube rack or well plate. Subsequently, the user could return to the first tube rack, and insert the pipette onto the first subset of tips 10 which were ejected previously, before moving back to the second tube rack or well plate with spacing 2V and expelling the fluid from those tips in a similar way to the first pass (but with a different subset of tubes/wells of the second tube rack or well plate selected for receiving the fluid). With this approach, the pipette designed for racks/well plates with a spacing of V could be used to transfer fluid from a rack/well plate with spacing V to a rack/well plate with spacing 2V.

Hence, in general this technique allows an existing pipette design for one spacing interval V to be used with tube racks or wells with a different spacing, by varying the pattern of release of the tips.

Figures 5 to 7 show different views of a specific embodiment of the tip ejector block 22 corresponding to the schematic of Figure 2. It will be appreciated that the exact shape shown in Figures 5 to 7 is just one example, but in general this shape exhibits the property summarised in Figures 2 and 3. Note that the triangular hatching shown in Figures 5 to 7 is provided to illustrate the shape of the surfaces of the tip ejector block 22 - these are not intended to show markings or engravings on the surface. The surfaces of the tip ejector block can be implemented a plain surface without any markings (although markings could optionally be provided if desired).

Figure 5 shows a view of the front end surface 24 of the tip ejector block, similar to the view shown in part B of Figure 2. The apertures A1 to A8 are shown the other way round so that A1 is the aperture on the right hand side shown in the view of Figure 5 and A8 is the aperture on the left hand side. As shown in Figure 5, the plateau portions 50 extend right up to the edge of the first subset of apertures 42 so that these will be close enough to the aperture to contact the top ends of the tips 10 when the user presses the ejector button when the pipette is in use. In contrast, the second subset of apertures 42 have surrounding the aperture a valley portion 52 which extends out to a greater radius away from the edge of the aperture 42. This means that the parts of the block 22 which are disposed around the second subset of apertures which are at the same level as the plateau portions 50 around the first subset of apertures are disposed far enough out from the centre of the aperture that they will pass over the top end of the tips 10 when in use so that the part of the block 22 which contacts the tips corresponding to the second subset of apertures is the contact surface portion 64 at the floor at the valley portions rather than any part higher up in line with the top of the plateau portions. By alternating the arrangement of the plateaus 50 and valleys 52 between adjacent apertures 42 as shown in Figure 5, this allows the alternating first and second subset of tips to be selected for ejection as described earlier.

Figure 6 shows two side views of the tip ejector block, the left hand view comprising a view along the long axis of the tip ejector block (i.e. along the x axis), and the right hand view comprising a view along the z axis. These views show that the portion 70 of the block 22 nearest the back end surface has a narrower width than the portion 72 nearest the front end surface. The narrower back end portion 70 is useful for enabling the tip ejector block 22 to sit within a slot in the ejector carriage 20. Clips 74 are provided to grip the outside of the ejector carriage 20 to fasten the tip ejector block 22 to the carriage.

Figure 7 shows a view similar to part A of Figure 2 showing the back end surface of the tip ejector block. As shown in Figure 7, each aperture may have the same diameter (sized to accommodate the diameter of the corresponding shafts 8 of the pipette 2). Hence, at the back end, the differences in profiling at the front end may not be visible.

Figures 5 and 6 illustrate how different apertures within the same subset can be provided with slightly different offset distances for the front end. In this example, the apertures A1 and A7 are provided with a ridge 76 formed on the plateau portion around the circumference of apertures A1 and A7, so that the plateau portions 50 for apertures A1 , A7 are slightly higher than plateau portions for the other apertures A3, A5 of the first subset. This can help to provide the minor differences in offset distance among the apertures of the first subset as described with respect to Figure 3 to reduce the ejection force. Similarly, the depths of the valleys 52 for the apertures of the second subset may vary slightly from aperture to aperture.

The tip ejector block shown in Figures 2, 3 and 5 to 7 is just one example and other examples may provide a different arrangement of the first and second subsets of apertures. For example, it would be possible to provide a tip ejector block 22 where the first subset of apertures comprise apertures spaced at a spacing interval of 4V (four times the normal spacing), and the remaining apertures are in the second subset. For example the first subset could comprise apertures A1 and A5, apertures A2 and A6, apertures A3 and A7, or apertures A4 and A8 (depending on design choice), with any remaining apertures being in the second subset.

Some implementations may also provide tip ejector blocks where the apertures of the first subset do not necessarily have a regular spacing. For example, the apertures of the first and second subset could be arranged in a pattern such as 11221122, where there is an alternating pattern between first apertures and second apertures but not necessarily a regular spacing.

Also, as shown in Figure 8, it is possible in some implementations for the front end surface of the tip ejector block 22 to be profiled so that the apertures are divided into three or more subsets where each subset of apertures has contact surface portions 46 with offset distances defined in a distinct band, separate from the bands used for other subsets. For example, Figure 8 shows an example where the first subset of apertures which have the offset distances in the lowest band 62 comprise apertures A1, A5 spaced at spacing interval 4V, for which the contact surface portions are on the upper surface of plateau portions 50 which are of a greater height than any other plateaus within the tip ejector block. A second subset of apertures A3, A7 (also having a spacing of 4V in this example) are formed with their contact surface portions on secondary plateaus 51 of shorter height than the plateaus 50 for the first subset of apertures, but where the secondary plateaus still extend above the base of the valleys 52 on which the contact surface portions for the remaining third subset of apertures A2, A4, A6, A8 are formed. Hence, as shown in Figure 8 the offset distances for the apertures group into three distinct bands 62, 64, 66 corresponding to first, second and third subsets of apertures respectively. Again, the maximum difference between the offset distances for any two apertures within the same subset is less than the minimum difference between the offset distances for any two apertures in different subsets. This means that, by user-distinguishable control actions on the control button 30, the user can select whether the first subset is released, whether both the first and second subsets are released, or whether all of the first, second and third subsets are released. This can be controlled by moving the ejection control button 30 by different distances.

It will be appreciated that these are just some examples of how the front end surface 60 of the tip ejector block can be profiled to divide apertures into different subsets which will have the tip ejector block contacting the corresponding tips on the shafts 8 at different timings as the tip ejector block 22 slides down the shafts 8 of the pipette 2.

The use of the tip ejector block 22 described above can help allow respective subsets of tips to be ejected in stages. Even without any modification to the ejection control mechanism, this may be sufficient to allow a user to move the ejection control button 30 by different amounts to select ejection of first, second or further subsets of tips. However, in some cases this may require very careful control of the amount by which the button 30 is pressed, which may be tricky for some designs of pipette (but not all). As shown in Figures 9 and 11, to assist the user with controlling whether only the first subset of tips are ejected or whether both first and second subsets are ejected, a biasing mechanism can be provided to provide resistance to depression of the ejection control button 30. The resistance means that the user has to expend more effort to depress the ejection control button which makes it easier to distinguish the respective positions at which different subsets of tips are released.

In the example of Figure 9, the biasing mechanism comprises an external spring 80 which is wound around the outside of the ejection control button 30, in the portion between the top surface 82 of the button and the top of the handle 4 of the pipette 2. When the user depresses the button 30 the spring 80 compresses and resists depression of the button. For example, the spring could be formed from a resilient piece of metal or plastic. A simple way of forming the spring 80 could be to cut a piece of plastic or other resilient material in a shape as shown in Figure 10, and then to cut out (remove) two circular portions 84 and a central square portion 86, leaving the outer portion marked 88. The material can then be folded about the central score line marked 90, to form the spring 80. The spring 80 can be fitted around the shaft of the ejection control button 30, with the shaft passing through the circular cut outs in the regions marked 84. For example, some pipettes may have an ejection control button where the top of the button can be pulled off the pipette and then replaced so this may allow the spring to fit around the shaft before it is replaced. Alternatively, the material used to form the spring may be flexible enough to clamp the spring onto the button without needing to remove the button (e.g. the material could be temporarily stretched to fit over the button) In some examples, the button body may not actually pass through the circular cut out region 84, but instead the spring can simply be bent over and wedged in the gap between the lip 82 at the top surface of the button and the upper surface at the top of the handle 4.

Of course, this is not the only way of forming such a spring. Springs can also be formed in other ways, e.g. with a coiled piece of metal. In some examples, the spring may (when at its resting state with no compression force applied) have a height which is less than the spacing between the top of the handle 4 and the bottom of the button lip 82, so that when the button 30 is depressed by the user, initially the spring is not compressed at all, but once the button 30 reaches a certain position corresponding to the height of the spring above the top of the handle 82, the spring starts to be compressed, increasing the resistance to further compression. Hence, it is not necessary for the spring to resist compression along the entire movement of the button 30.

Also, the particular means of providing resistance to actuation of the ejection control mechanism can vary depending on the pipette design. Figure 11 shows a number of alternative examples of biasing mechanisms. Three different examples of possible biasing mechanisms are shown in Figure 11 , but it will be appreciated that only one needs to be provided in practice, the three examples being shown in the same diagram simply to reduce the number of diagrams.

Example 1 is similar to the case shown in Figure 9, where a spring is provided around the ejection control button 30. It will be appreciated that springs could also be fitted at other parts of the mechanism, e.g. internally around part of the arm or other cross-pieces linking the ejection control button 30 to the carriage 20. The resistance force of the spring resisting further compression of the button increases with increasing compression of the spring, so it is harder to move the button 30 from a first control position 104 to a second control position 106 than from the starting position to the first control position 104. This makes it easier for the user to select which position to move the button 30 to and hence which subset of tips 10 is ejected.

As shown in example 2 of Figure 11 , another approach can be to provide a set of opposed magnets 100, which are positioned such that, as the ejection control button 30 is depressed, the opposed magnets approach each other. As the magnets are positioned with like poles (e.g. N and N, or S and S) facing each other, then as the magnets approach each other then it becomes harder and harder for the user to carry on depressing the ejection control button 30. This means that when the ejection control mechanism is moved from a first control position 104 towards a second control position 106, the force required for the user to move the mechanism to the second position increases as the opposed magnets 100 approach each other, so that the user can easily distinguish the actions required for ejecting the first/second subsets of tips, based on the extra effort required to release the second subset compared to the first subset.

A third example is shown in Figure 11 where instead of providing opposed magnets, a set of attracting magnets 110 are provided at positions such that, as the ejection mechanism moves past the first control position 104 to the second control position 106, the magnets 110 move apart. As in the second example, one of the magnets 110 can be disposed on a moving part of the ejection control mechanism and the other magnet on a static part of the pipette 2, e.g. on part of the pipette body 6. The magnets are positioned so that unlike poles face each other (N on one of the magnets and S on the other). The magnets are closer together when the ejection mechanism reaches the first control position 104 than at the second control position 106. Therefore, for the user to move the ejection control mechanism from the first control position to the second control position, this requires the user to overcome the attractive force of the attracting magnets 110, again providing the requirement for additional effort to be applied which allows the user to easily distinguish the two control positions 104 and 106.

Hence, in general it can be useful for the ejection control mechanism to have some functionality which enables the user to distinguish when the first and second control positions are reached (the first and second control positions may correspond to the positions when the contact surface portions 46 reached the tops of the first and second subsets of tips respectively, based on the different offset distances between the leading edge of those contact surface portions and the leading edge of the tip ejector block 22 as a whole).

It will be appreciated that the particular design for the biasing mechanism may vary considerably depending on the layout of the pipette. The examples shown in Figure 11 using springs or magnets can be useful for an implementation where an existing pipette is to be retrofitted with a new tip ejector block 22, as the addition of magnets or a spring may be simple to fit in retrospect. However, for standalone pipette designs which are designed from the outset to have a tip ejector block 22 with a front end surface with the alternating profile as described above, it would be possible to provide other ways for the user to distinguish whether the tip ejector block 22 has reached the first position or the second position. For example, an internal spring could be provided within the pipette body 6 which is hidden from view of the user when in use, to provide resistance to depression of the control lever 30. Also, in a standalone pipette design, it would be possible to provide two entirely separate levers or buttons for the user to control release the first subset of tips or the second subset of tips as desired. Also, different electronic commands could be provided in an automated embodiment where ejection is controlled automatically by electronic means. Hence, the examples shown in Figure 11 are not exhaustive, and there may be other ways of allowing the user to distinguish which subsets of tips to release. Nevertheless the examples shown in Figure 11 are cheap to fit and can be suitable for adapting an existing pipette.

In the examples described above, the tip ejector block 22 is a solid object with no moving parts, which has a fixed configuration profiled to provide staged ejection of tips. However, as shown in the examples of Figures 12 and 13, it is also possible to provide tip ejector blocks 22 which have an adjustable front end profile, so that the user can select different patterns of tip release. Such ejector blocks 22 have at least one configuration in which the front end surface comprises alternating first/second subsets of apertures with the contact surface portions 42 at different offset distances relative to the leading edge of the front end surface, as described earlier, but may also have other configurations which the user can select to provide different staged ejection patterns.

Figure 12 shows a first example of a tip ejector block 22 capable of altering the configuration of the front end surface. Each aperture 42 has a valley portion 52 formed around the edge of the aperture, which is set back from the leading edge of the front end surface of the tip ejector block similar to the valley portions 52 in the example described earlier. Also, each aperture 42 has a folding cover portion 120 which can be pivoted about a first edge 122 of the front end surface to fold the cover portion 120 so that it covers the corresponding aperture 42. The cover portion 120 itself includes an aperture 121 to allow the shafts 8 of the pipette 2 to pass through the block when in use, even when the cover is fastened over the aperture 42. A clip portion 124 on the cover portion 120 clips to a second edge 126 on the opposite side of the front end surface from the first edge, to hold the cover portion 120 in position to cover the aperture 42 (the first/second edges 122, 126 run parallel to the first axis (x axis) along which the apertures are disposed).

For the apertures for which the cover portion 120 is left unfastened, the contact surface portion 42 is formed by the base of the valley portions 52. For apertures for which the cover portion 120 is fastened down by clipping it to the second edge 126, the cover forms a plateau portion 50 similar to the examples above, and the contact surface portion 42 is formed by the top of the cover 120, which will have a smaller offset distance than the offset distance for the valley portions 52, since the cover 120 will contact the tips on the corresponding shafts 8 of the pipette 2 earlier than the valley portions 52 of other apertures when the tip ejector block is in use. Hence, the apertures with the covers fastened down represent a first subset of apertures and the apertures with the covers left unfastened represent a second subset of apertures. The user can select which apertures have the covers fastened/unfastened, to vary the pattern with which the apertures are divided into the first/second subsets. If the user fastens down every other cover 120, then this is similar to the example of Figure 2 with the first subset of apertures comprising apertures with spacing of 2V. If the user chooses to fasten down every fourth cover then this enables the same block to be adapted for use with a rack of spacing 4V. Other more arbitrary patterns are also possible, depending on user choice.

Figure 13 shows a second example of a tip ejector block 22 with variable offset distance for each aperture. As in Figure 12, each aperture 42 has a valley portion 52 formed around the edge of the aperture, which is set back from the leading edge of the front end surface of the tip ejector block similar to the valley portions 52 in the examples described earlier. Again, each aperture 42 is associated with a cover portion 120 (again comprising an aperture 121) which can be manipulated to provide a plateau region 50 with a smaller offset distance than the valley portion 52 for a given aperture. However, in the example of Figure 13, the cover portions 120 are slidable through a slot 128 in a side wall of the tip ejector block 22, so that they can selectively cover the apertures 42 or be left outside the side wall 130 depending on user choice. In the example configuration shown in Figure 13, the cover portion 120 for aperture A1 has been slid into position to cover the underlying aperture 42, so aperture A1 is a member of the first subset, but all the other apertures have their covers positioned outside the side wall, so that these apertures are members of the second subset as the contact surface portions 42 for these apertures will be the valley portions 52. The user can select additional apertures to become part of the first subset by sliding more of the cover portions 120 in to cover the apertures.

Hence, in general, various mechanisms are possible to allow the user to vary the configuration of which particular apertures are part of the first/second subset. For example, each aperture may be associated with a valley portion surrounding the aperture, and a cover portion which in a first position acts as the contact surface portion for the aperture and in a second position is removed to expose the valley portion so that the valley portion acts as the contact surface portion for the aperture. Hence, the offset distance for a given aperture may be smaller when the cover portion is in the first position than when the cover portion is in the second position. It will be appreciated that the pivoting and sliding cover portions of Figures 12 and 13 are just one way of adjusting the cover portions. Another example could provide cover portions which are entirely removable from the rest of the tip ejector block 22, so that the user can choose either to clip the cover portions onto the side walls of the tip ejector block 22 (similar to the clipping by the clip portion 124 in Figure 12 onto the side wall 126), or to remove the cover portions entirely, to define the subset membership of the different apertures. The examples described above describe a tip ejector block 22 for use with a manually operated pipette 2, for which the user moves manually operated buttons or levers 18, 30 to control take up and expulsion of fluid and ejection of tips from the pipette. However, as shown in Figure 14 it is also possible to use a similar tip ejector block 22 with an automated pipetting machine 140 which provides automated control of the fluid take up and expulsion functions and the ejection of the tips, by electronic means using an automated control unit 142. In the automated pipetting machine 140, there may be an ejector mechanism 144 which is electronically controlled by the automated control unit 142 to move the tip ejector block 22 over the shafts 8 of the pipetting machine to eject the tips from the shafts.

Also, as shown in Figure 14 for such an automated machine 140, rather than providing a one-dimensional (1D) array of shafts 8 for carrying tips with the shafts aligned along an axis in a linear direction, the automated machine may comprise a two-dimensional (2D) array of shafts arranged in a grid pattern. This allows the number of channels which can be processed in parallel, which can be useful for certain industrial processes for example. Hence, the tip ejector block 22 may, as shown in the upper part of Figure 14, comprise a block formed with a 2D array of apertures 42. The apertures may be divided into first and second subsets similar to the examples described above for a 1D embodiment, by profiling the front end surface of the block 22 to have plateaus and valleys similar to the example of Figure 2, so that the first subset of apertures 150 have contact surface portions around them which will reach the tops of the tips earlier than the contact surface portions around a second subset of apertures 152. Hence, by fitting the tip ejector block 22 with such a front end surface profile to the automated pipetting machine 140 shown in Figure 14, the ejector mechanism can eject a first subset of tips which are on the shafts 8 extending through the first subset of apertures 140 in a first stage of tip ejection, and then subsequently eject remaining tips in a second stage of tip ejection by the ejector mechanism 144 further moving the tip ejector block 22 down based on electronic commands issued by the automated control unit 142.

While Figure 14 shows use of a 2D array of shafts 8 and 2D ejector control block for an automated machine 140, it would also be possible to provide a manually operated tool with such a 2D array of shafts and hence the ejector control block for a manually operated tool could also provide a 2D array of apertures similar to the one shown in Figure 14.

In the example of Figure 14, a similar resistive mechanism may (optionally) be provided to that described earlier.

The above examples describe the tip ejector block 22 being used with a multi-channel pipette 2 which is able to draw fluid into tips 10 disposed on the end of the shafts 8. However, the tip ejector block could also be used with other types of other multi-channel laboratory tool. For example Figure 15 shows an example of a magnetic bead carrying device 200. For conciseness, the parts of the device which are the same as in the pipette Figure 1 are not shown. Hence, as in the pipette 2, the device may have a body 6 connected to a handle 4 and a number of shafts 8 extending down from the body, and an ejection control mechanism 20, 22, 26, 28, 30 similar to the example of Figure 1. However, the magnetic bead carrying device differs from the pipette in that instead of providing a fluid aspirating mechanism, instead the control arm 18 is connected to a set of magnetic rods 202 which extend down into the respective shafts 8 of the device and which can be retracted and extended by moving the control lever 18 up and down, to change the relative height of the magnetic rods 202 within the corresponding shafts 8.

Hence, when tips are disposed on the ends of the shafts, the magnetic rods 202 can be moved down into the part of the shafts 8 that are within the tips 10, so if the tips are inserted into a container comprising magnetic beads (potentially carrying biological sample) then the magnetic beads can be attracted onto the edges of the tips by the magnetic field exerted by the magnetic rods 202. When the magnetic beads need to be released from the tips 10 into a set of wells, tubes or other containers, the tips 10 can be inserted into the containers, and the control arm 18 moved up to retract the rods 202 from the tips 10, so that the beads fall off the tips 10 into the containers.

The design of the tip ejector block 22 for use with the magnetic bead carrying device 200 can be exactly the same as for a pipette with a corresponding inter-shaft spacing. Other than the difference in that instead of a fluid aspirating mechanism the magnetic rod arrangement is provided, other aspects of the magnetic bead carrying device 200 and the use of the tip ejector block 22 can be the same as described above. Hence, it will be appreciated that the techniques discussed above which provide alternating profiles of the front end surface of the tip ejector block 22 can also be provided for magnetic bead carrying devices or to other types of multi-channel laboratory tool which have a number of shafts 8 for carrying disposable tips to be ejected from the shafts. It is also possible to provide an automated magnetic bead carrying device similar to the automated pipetting machine 140 described above.

For such a magnetic bead carrying device 200, the ejector block 22 described above can enable magnetic beads to be transferred from a rack or well plate with spacing V to a rack or well plate with spacing 2V. This can be done by collecting the tips 10 from a first tube rack with spacing V, and then inserting the tips into a set of tubes or wells with spacing V that contain the magnetic beads, with the magnetic rods 202 extended into the tips so that the magnetic beads are attracted onto the tips 10. The user can then eject the first subset of tips. While holding the device 200 above a further set of tubes/wells with spacing 2V (e.g. with sufficient clearance so that the magnetic rods associated with the previously ejected first subset of tips do not engage with the further set of tubes/wells), the user can then retract the rods 202 to allow the magnetic beads to drop from the remaining second subset of tips into the tubes/wells. After ejecting the second subset of tips, the user can then return to collect the first subset of tips temporarily held in the first tube rack (and extend the magnetic rods 202 when doing so to ensure the magnetic beads previously on the first subset of tips will once more be attracted onto the tips), and then transfer these beads to the tubes/wells of spacing 2V in a similar way to the tips previously transferred. Again, it will be appreciated that users may find other modes of use for the same device, different to the one described above, so this is not the only way of using the device 200.

As mentioned above, in one example the tip ejector block 22 may be manufactured by an additive manufacturing (or 3D printing) process such as stereolithography, fused deposition modelling, selective laser melting, or any other additive manufacturing technique. In an additive manufacturing process, layers of the tip ejector block 22 are formed layer-by-layer by adding additional material to the block laid on top of previously formed layers. Additive manufacturing processes are capable of forming objects with relatively intricate patterns. Also, additive manufacturing can provide a relatively efficient way of distributing tip ejector blocks to customers since rather than manufacturing the block and then transmitting the block itself it would also be possible to transmit to a customer an electronic data structure which can be read by the customer’s control computer to control an additive manufacturing machine at the customer’s end to manufacture the tip ejector block 22.

As shown in Figure 16, a shape-representing data structure 300 is provided which provides control data representing the shape of the tip ejector block 22 to be manufactured. For example the shape-representing data structure 300 can be a computer aided design (CAD) file which represents a three-dimensional model of the shape of the block, or could be a data structure which defines, layer-by-layer, information on the two-dimensional extent of each layer which will form the block. The shape-representing data structure 300 may be input to a control computer 302 associated with an additive manufacturing machine 304 such as a 3D printer. The control computer may convert the shape-representing data structure 300 into manufacturing commands which control the scanning of the additive manufacturing 304, such as controlling positions of lasers which cure resin or fuse powder material to form each layer of the block to be manufactured. The shape-representing data structure 300 may be stored on a recording medium which may be a non-transitory recording medium.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A tip ejector block for ejecting tips from tip-carrying shafts of a multi-channel laboratory tool, the tip ejector block comprising: a plurality of apertures for receiving the tip-carrying shafts of the multi-channel laboratory tool, where the plurality of apertures are spaced along a first axis at regular intervals of a predetermined spacing interval; and a front end surface comprising a plurality of contact surface portions, each contact surface portion surrounding a respective one of the apertures for contacting the tip on a corresponding one of the tip-carrying shafts to eject the tip when in use; in which: in at least one configuration of the tip ejector block: the apertures comprise a first subset of apertures and a second subset of apertures, where the first subset of the apertures are interleaved with the second subset of the apertures in an alternating pattern; and when the tip ejector block is moved along a second axis perpendicular to the first axis with the front end surface facing a direction of travel, the contact surface portions associated with each of the first subset of apertures would reach a given position along the second axis before the contact surface portions associated with each of the second subset of apertures reach the given position.

2. The tip ejector block according to claim 1 , in which: an offset distance for a given contact surface portion surrounding a given aperture is defined as a distance, along the second axis, between a leading edge of the given contact surface portion and a leading edge of the front end surface as a whole; and in said at least one configuration of the tip ejector block, the offset distance for the contact surface portions associated with each of the second subset of apertures is greater than the offset distance for the contact surface portions associated with each of the first subset of apertures.

3. The tip ejector block according to any preceding claim, in which, the apertures comprise at least one aperture of the first subset which is disposed between two apertures of the second subset, and at least one aperture of the second subset which is disposed between two apertures of the first subset.

4. The tip ejector block according to any preceding claim, in which the first subset of the apertures are spaced along the first axis at regular intervals of a wider spacing interval greater than the predetermined spacing interval; or the second subset of the apertures are spaced along the first axis at regular intervals of the wider spacing interval greater than the predetermined spacing interval.

5. The tip ejector block according to claim 4, in which the wider spacing interval is one of: twice the predetermined spacing interval; and four times the predetermined spacing interval.

6. The tip ejector block according to any preceding claim, in which the front end surface comprises plateau portions and floor portions between the plateau portions, where the contact surface portions for the first subset of apertures comprise the plateau portions and the contact surface portions for the second subset of apertures comprise the floor portions.

7. The tip ejector block according to any preceding claim, in which, for the at least one configuration of the tip ejector block: the apertures also comprise a third subset of apertures; and when the tip ejector block is moved along the second axis with the front end surface facing a direction of travel, the contact surface portions associated with each of the second subset of apertures would reach the given position along the second axis before the contact surface portions associated with each of the third subset of apertures reach the given position.

8. The tip ejector block according to any preceding claim, in which when the tip ejector block is moved along the second axis with the front end surface facing the direction of travel, the contact surface portions associated with at least two apertures of the first subset would reach the given position along the second axis at different times.

9. The tip ejector block according to any preceding claim, in which an offset distance for a given contact surface portion surrounding a given aperture is defined as a distance, along the second axis, between a leading edge of the given contact surface portion and a leading edge of the front end surface as a whole; and at least one of the plurality of apertures has a contact surface portion with an adjustable offset distance.

10. The tip ejector block according to any preceding claim, in which the tip ejector block is retrofittable to an existing multi-channel laboratory tool.

11. A computer-readable storage medium storing a shape-representing data structure representing a shape of the tip ejector block according to any preceding claim, for controlling an additive manufacturing machine to manufacture the tip ejector block by an additive manufacturing process.

12. A multi-channel laboratory tool comprising: a plurality of tip-carrying shafts for carrying tips ejectable from the tip-carrying shafts; the tip ejector block according to any preceding claim; and an ejection mechanism to actuate movement of the tip ejector block along the tip carrying shafts to eject the tips from the tip-carrying shafts.

13. The multi-channel laboratory tool according to claim 10, in which: in response to a first user-selected action, the ejection mechanism is configured to move the tip ejector block along the tip-carrying shafts parallel to the second axis; and in response to a second user-selected action distinguishable by the user from the first user-selected action, the ejection mechanism is configured to move the tip ejector block further along the tip-carrying shafts beyond a position reached in response to the first user-selected action.

14. The multi-channel laboratory tool according to claim 13, in which the first user-selected action comprises mechanical displacement of a button or lever from a starting position to a first control position, and the second user-selected action comprises further mechanical displacement of the button or lever beyond the first control position to reach a second control position.

15. The multi-channel laboratory tool according to claim 14, comprising a biasing mechanism to resist displacement of the button or lever between the first control position and the second control position, to assist the user with distinguishing the first control position and the second control position.

16. The multi-channel laboratory tool according to claim 15, in which the biasing mechanism comprises a spring.

17. The multi-channel laboratory tool according to claim 15, in which the biasing mechanism comprises one of: opposed magnets positioned to provide a separation force which increases as the button or lever is displaced from the first control position to the second control position; and attracting magnets positioned to provide an attraction force which decreases as the button or lever is displaced from the first control position to the second control position.

18. The multi-channel laboratory tool according to any of claims 13 to 17, in which: in response to a third user-selected action distinguishable by the user from the first user- selected action and the second user-selected action, the ejection mechanism is configured to move the tip ejector block further along the tip-carrying shafts beyond a position reached in response to the second user-selected action.

19. The multi-channel laboratory tool according to any of claims 12 to 18, in which the multi channel laboratory tool comprises a manual tool portable by a user.

20. The multi-channel laboratory tool according to any of claims 12 to 18, in which the multi channel laboratory tool comprises an automated tool having an automated control mechanism for controlling ejection of the tips from the tip-carrying shafts.

21. The multi-channel laboratory tool according to any of claims 10 to 20, in which the multi channel laboratory tool comprises a multi-channel pipette.

22. The multi-channel laboratory tool according to any of claims 10 to 20, in which the multi channel laboratory comprises a magnetic-bead-carrying tool, where the plurality of tip-carrying shafts comprise magnetic rods for attracting magnetic beads onto the tips carried by the tip carrying shafts.

23. A multi-channel laboratory tool comprising: a plurality of tip-carrying shafts for carrying tips ejectable from the tip-carrying shafts, where the tip-carrying shafts are spaced at regular intervals of a predetermined spacing interval; and an ejection mechanism to eject the tips from the tip-carrying shafts; in which: in response to a first user-selected action, the ejection mechanism is configured to eject the tips from a first subset of the tip-carrying shafts; in response to a second user-selected action distinguishable by the user from the first user-selected action, the ejection mechanism is configured to eject the tips from a second subset of the tip-carrying shafts; and the first subset of the tip-carrying shafts are interleaved with the second subset of the tip carrying shafts in an alternating pattern.