Patent Description:
Automated and semi-automated liquid handling systems often include pipetting heads for either <NUM> or <NUM> disposable pipette tips. A <NUM> pipetting head has an array of <NUM> by <NUM> tip mounting shafts with the centerline spacing between the adjacent shafts being <NUM>. A <NUM> pipetting head has an array of <NUM> by <NUM> mounting shafts with the centerline spacing between the adjacent shafts being <NUM>. The spacing is set by ANSI/SLAS Microplate standards (formerly known as SBS format). The American National Standards Institute/Society for Laboratory Automation and Screening (ANSI/SLAS) has adopted standardized dimensions for microplates:.

These standards have been developed to facilitate the use of automated liquid handling equipment with plastic consumable products from different manufacturers. Automated or semi-automated liquid handling systems having a matrix of fewer mounting shafts such as a <NUM> pipetting head or more mounting shafts such as a <NUM> pipetting head are also used in the field, although the most common are the <NUM> and <NUM> heads. These automated or semi-automated liquid handling systems are typically designed with platforms located underneath the pipetting head, which contain one or more nesting locations for microplates, racks of microtubes or reservoirs for holding samples or reagents. In the art, microplates are sometimes referred to as well plates, and microtubes are sometimes referred to a sample tubes. The nests are sized in accordance with the outside dimensions for microplates for the SBS standard (now ANSI/SLAS) in order to align each of the <NUM> or <NUM> pipette tips with the center points of the respective wells in the microplate on the platform.

As mentioned, reservoirs for holding samples or reagents can also be configured to be placed on the platform in the nest. Reservoirs typically have a common basin instead of individual wells and are known to have either a flat bottom or a patterned bottom in order to reduce residual liquid waste. It is also known to use a disposable reservoir liner to avoid the need to clean and/or sterilize reservoirs before starting a new procedure. In addition to automated and semi-automated systems, handheld pipettes are used to draw reagents or samples from reservoirs, microplates or microtubes. One reservoir kit that uses a liner is disclosed in <CIT> is particularly well suited for use with handheld pipettes. Many reservoirs and liners are made of polystyrene which is naturally hydrophobic. The hydrophobic surface causes liquid to bead up and pool during final aspiration which is generally thought to facilitate liquid pick up and reduce the residual volume.

One problem that has been found to occur with the use of reservoirs or disposable reservoir liners is that one or more of the mounted pipette tips may engage the surface of the liner bottom when the pipette head is lowered. A pipette tip engaged with the surface of the bottom wall can unfortunately create a vacuum within the tip when the head aspirates. The vacuum within the tip increases as aspiration continues and the orifice is eventually closed off. This situation can lead to inaccurate pipetting, but can also lead to contamination of the pipetting head which is a serious issue. When a pipette tip that has vacuum engaged the bottom wall releases, the reagent or sample, now driven by a significant pressure difference, often sprays upward beyond the pipette tip and the mounting shaft into the respective piston cylinder. If this occurs, it may be necessary to disassemble, clean and sterilize the entire pipette head.

The problem of pipette tips possibly engaging the bottom of a container and forming a vacuum during aspiration can also occur in reservoirs without liners, or in other containers typically used for pipetting such as microtubes or microplates. In all of these applications, it is often desirable to reduce residual volume or liquid hang-up in the container when attempting to fully aspirate all the liquid from the container. To this end, pipette tips are typically lowered as close to the bottom wall of the container without contacting the bottom wall as reasonably possible in order to reduce the residual volume of liquid that cannot be aspirated. In multi-channel pipetting systems, even automated multi-channel systems where the height of the pipetting head can be controlled precisely, one or more pipette tip orifices can become misaligned with the other tip orifices because, for example, a pipette tip is mismounted or deformed. Tip misalignment can lead to the tip engaging the bottom wall and forming a vacuum. Even if all of the pipette tips are aligned properly, it is possible that the portions of bottom wall in the container or container(s) corresponding to the locations of the pipette tips are not precisely aligned on a plane level with the pipette tip orifices. This sort of unevenness can occur, e.g., when one or more microtubes are not completely seated in the tube rack, or when a liner is not fully seated in a reservoir base or is slightly deformed, and can also lead to one or more pipette tips engaging the bottom wall when trying to aspirate the final volume from the container. <CIT>, <CIT>, <CIT>, <CIT> and <CIT> all disclose prior art systems.

The invention relates primarily to the placement of anti-vacuum channels on the bottom wall of receptacles in pipetting containers used in clinical and research laboratory products, such as laboratory reservoirs for liquid samples and reagents, reservoir liners, microtubes, PCR tubes, microplates and PCR strips and plate; as claimed in claim <NUM>. The use of the anti-vacuum channels enables a pipette tip to engage the bottom wall of the receptacle without allowing vacuum pressure to accumulate within the tip while aspirating. Suitably sized ribs can be used for this purpose as well; however, use of anti-vacuum channels has been found to be particularly well suited for also reducing dead volume when pipetting residual liquid from the container. The capillary action of the channels tends to draw the liquid into the respective groupings of channels, and this reduces the minimum required working volume for the receptacle because the pipette tip is able to draw liquid from the channels at any location within the respective channel grouping. Connecting groupings of channels fluid dynamically has been found to further reduce dead volume and the minimum working volume in some applications.

In a first exemplary embodiment of the invention, a laboratory reservoir kit has a disposable liner that is held within a reusable reservoir base. The kit is configured to be used with a hand-held pipette, e.g. a multi-channel pipette having disposable pipette tips mounted along a line. The reusable reservoir base provides a stable support on a flat surface, such as a laboratory bench top. The base has an elongated basin including a pair of end walls, a longitudinal trough extending along a bottom surface of the basin and a pair of longitudinal sidewalls extending between the end walls,. The longitudinal sidewalls slant outward as the sidewall extends upward to form a portion of the basin, with the trough at the bottom of the sidewalls.

The disposable liner also has a pair of longitudinal sidewalls and a longitudinal trough extending between end walls to define at least one liner basin in which liquid sample or liquid reagent is held for pipetting. A peripheral flange extends outward from a top of the liner basin such that the peripheral flange rests on a rim of the reusable base when the disposable liner is set in place within the reusable base. A plurality of anti-vacuum channels is located on an upper surface of the liner trough and exposed upwardly into the liner basin in which liquid sample or liquid reagent is held for pipetting. The liner trough desirably has a rounded cross section to accommodate the linear placement of groupings of anti-vacuum channels longitudinally along the bottom of the trough. Desirably, each grouping of anti-vacuum channels includes at least one pair of intersecting channels and the liner includes additional channels that extend between groupings in order to connect adjacent groupings fluid dynamically. As mentioned, connecting the groupings of channels can help to reduce residual dead volume or lower the minimum working volume, especially when the wettability of the liner is appropriately selected by treating polystyrene or polypropylene with corona treatment or otherwise. The treatment is sufficient to render the measured surface tension of the bottom wall of the liner greater than or equal to about <NUM> dynes, which is the surface tension for natural water. Polypropylene is not as stiff as polystyrene but may be desired in certain applications because it provides better chemical resistance.

In some embodiments, the liner can include one or more walls spanning between the longitudinal sidewalls of the liner, to create separate basins in the liner.

The liner is made of transparent plastic, and an inside surface of the sidewall of the basin on the reusable base has distinct liquid volume graduation marks. The liquid volume graduation marks on the sidewall of the basin are calibrated to measure a volume of liquid sample contained in the one or more basins of the disposable liner and are observable through the transparent disposable liner when the disposable liner is set in place within the reusable base.

In other exemplary embodiments of the invention, a laboratory reservoir kit with a disposable liner and a reusable reservoir base is configured with anti-vacuum channels for use with SBS formatted <NUM> or <NUM> pipetting heads. Desirably, in these embodiments the reusable reservoir base has outside flange dimensions compatible with nests configured to hold SBS-formatted well plates and reservoirs (i.e. ANSI/SLAS <NUM>-<NUM>: Microplates - Bottom Outside Flange Dimensions). If the reservoir is made to be used with a <NUM> pipetting head, the disposable liner contains a matrix of <NUM> groupings of anti-vacuum channels with a center point for each grouping spaced <NUM> from the center point of adjacent groupings, consistent with SBS (ANSI/SLAS) formats. If the disposable liner is designed to be used with a <NUM> pipetting head, the liner desirably contains a matrix of <NUM> groupings of anti-vacuum channels with the center point for each grouping spaced <NUM> from the center point of adjacent groupings, again consistent with SBS (ANSI/SLAS) formats. The disposable liner can also be made with more or less groupings depending on the intended use of the liner; however, in each case the groupings should be centered at the center point at which it is expected that the respective pipette tips on the pipetting head may contact the liner. In some embodiments, the liner contains a matrix of <NUM> groupings of anti-vacuum channels with adjacent center points spaced <NUM> apart, as well as a matrix of <NUM> groupings of anti-vacuum channels having center points spaced apart <NUM>. In this manner, the liner is configured to be used both with a <NUM> pipetting head or a <NUM> pipetting head.

The groupings of the anti-vacuum channels can take on various configurations in accordance with the invention. The goal is to provide a channel configuration that will provide a fluid accessible void underneath the orifice of the respective pipette tip even if the pipette tip is somewhat off center, which can occur in an automated pipetting system, for example, when a pipette tip is not mounted straight or the tip is slightly deformed. One desired grouping configuration includes a first pair of perpendicular and intersecting channels with the intersection of the channels defining a center point for the grouping, and a second pair of perpendicular channels rotated <NUM>° from the first pair where the second pair of channels are aligned to intersect at the center point but are interrupted in the vicinity of the center point. It is desirable that the channels have a constant width and a constant depth, and that the width of the channels is selected so that the distance across the intersection is less than the outside orifice diameter of the smallest sized pipette tips that will likely be used with that liner. For example, if a <NUM>µl pipette tip has an outside orifice diameter of <NUM>, then the width of the channels should be less than <NUM> to ensure that the distal end of the pipette tip cannot fit into the channels at the intersection which may result in creating a vacuum. For a <NUM> application, the desired channel width using the above described grouping configuration is also <NUM>. Likewise, for a <NUM> head application, the desired width is <NUM>. The grouping may also have other channels located away from the center point towards the perimeter of the grouping in order to provide a larger region covered by anti-vacuum voids in the event that the pipette tip orifice is off center because of how the tip is mounted or constructed, or in the event it is used with a hand-held pipette. In one embodiment, the channel grouping includes a third pair of parallel linear channels spanning between the second pair of perpendicular channels and crossing the first pair of perpendicular intersecting channels. In another embodiment, a circular channel intersects each of the first and second pair of channels.

In most embodiments for SBS-formatted pipetting heads, the bottom wall of the disposable liner is otherwise flat, and the groupings of anti-vacuum channels are located at the center point for either a <NUM> pipetting head or a <NUM> pipetting head configuration or both. In other embodiments, the bottom wall of the disposable liner is patterned with an array of recesses in either the <NUM> or the <NUM> configuration. A grouping of anti-vacuum channels is located within each recess. Ridges are formed at the interfaces of the adjacent recesses, and the low point of each of the multiple recesses in the bottom of the wall of the liner lies in a common plane. The recesses desirably have a curvature in the shape of a partial sphere, although other configurations are possible in accordance with the invention.

The disposable liner desirably is made of a transparent plastic material, such as clear molded and corona treated polystyrene or polypropylene (surface tension greater than or equal to <NUM> dynes), and has a shape that closely follows the contour of the basin of the reusable base, in part to facilitate viewing of liquid volume graduation marks on the side walls of the base. Also desirably, the side walls of the reusable reservoir base have distinct liquid volume graduation marks on the surface of the side wall forming a portion of the basin. These liquid volume graduation marks are calibrated to measure a volume of liquid sample contained in the transparent disposable liner and are observable when the disposable liner is set in place within the reusable base. Further, one or more sides of the reusable base may contain one or more viewing windows so that a user can easily view the amount of liquid contained in the disposable liner, the printed graduations and the location of the pipette tips in relation to the anti-vacuum groupings. The viewing window can be a narrow window or it can be relatively wide as long as the base still has enough support for the disposable liner.

In some circumstances, it may be desirable to provide one or more upstanding walls in the liner between rows or columns of the groupings of anti-vacuum channels. Walls sealed at the bottom of the liner can be molded into the liner, and effectively separate the contained volume into multiple basins for liquid reagent or liquid samples. The walls can also serve as a splashguard. Alternatively, a removable baffle or splashguard, having upstanding walls between two or more rows or columns of the groupings of anti-vacuum channels can be used, without sealing at the bottom wall of the liner. In this configuration, the splashguard does not separate the liner basin into separate sealed volumes or basins.

In another embodiment, the invention is directed to a reservoir, designed to be used without a liner, and further configured with anti-vacuum channels on the bottom wall to prevent pipette tips from vacuum engaging the bottom wall of the reservoir. The bottom wall has a generally rectangular shape configured to enable a matrix of pipette tips to aspirate liquid from the volume in the liner basin. The reservoir is preferably made from molded polystyrene that is corona treated or otherwise treated to increase the wettability of the bottom wall. The reservoir desirably has an outside flange dimensioned in accordance with the SBS format. It is possible that the anti-vacuum channels extend over the entire bottom wall of the reservoir basin, however it is preferred that the bottom wall include a matrix of groupings of anti-vacuum channels. For reservoirs designed to be used with <NUM> channel pipetting heads, it is desirable for the reservoir to include a matrix of <NUM> groupings of anti-vacuum channels with the center point for each grouping spaced <NUM> from the center point of adjacent groupings. For reservoirs designed to be used with <NUM> pipetting heads, it is desirable for the bottom wall of the reservoir to have a matrix of <NUM> groupings of anti-vacuum channels with a center point for each grouping spaced <NUM> from the center point of adjacent groupings. The geometry in the dimensions of the anti-vacuum channels and grouping of channels is suitably the same or similar to that described in connection with the reservoir liners above.

In one particularly desirable embodiment, the bottom wall of the reservoir contains both a matrix of <NUM> groupings with <NUM> spacing and a matrix of <NUM> groupings with <NUM> spacing, and it is further desirable that each of the <NUM> groupings shares one or more channels with <NUM> groupings of the <NUM> anti-vacuum channel groupings.

In an alternative reservoir embodiment, the bottom wall of the reservoir is patterned with recesses, instead of flat, and includes grouping of anti-vacuum channels located within each recess. In another alternative embodiment, the reservoir includes at least one sealed wall between two adjacent rows of anti-vacuum channel grouping or between two adjacent columns of anti-vacuum channel groupings in order to separate the reservoir basin into separate volumes. A splashguard not sealed at the bottom can also be used in connection with the reservoir.

Another embodiment of the invention is directed to a laboratory microtube that includes a receptacle for holding liquid reagents or samples and a removable cap for closing the microtube. In addition, the receptacle will typically have cylindrical sidewalls and a bottom wall, with at least a portion of the bottom wall being generally flat and horizontal. In accordance with the invention, the upper surface of the bottom wall has multiple anti-vacuum channels extending upwardly towards the volume in which the liquid sample or liquid reagent is held. The configuration and dimensions of the groupings of anti-vacuum channels is selected so that a void will be underneath the orifice of a tip pressed against the surface of the bottom wall at any point. The microtubes are made of molded polypropylene, and corona or otherwise treated so that the bottom wall of the microtube has enhanced wettability; providing a surface tension of greater than or equal to <NUM> dynes which is the surface tension of natural water.

Microtubes are typically stored in racks, e.g. <NUM> tubes in an 8x12 array, and the tube height might be uneven. This can happen for example if one or more of the tubes are not completely seated in the rack. When this occurs, the pipette tip can press against the bottom wall of the tube. This can also occur if one or more pipette tips are mismounted, or if the pipetting system lowers the pipetting head too low into the microtubes in a rack. The anti-vacuum feature is useful to address each of these issues. Also, the anti-vacuum feature may be helpful when using a hand-held single channel pipette by allowing the user to engage the bottom wall of the tube without creating a vacuum engagement. The advantage of having the anti-vacuum feature when using a hand-held pipette is also applicable to use with reservoirs and reservoir liners.

In another embodiment, the invention is directed to a microplate, for example, an SBS formatted microplate having a plurality of separate wells arranged in columns and rows. Each well is configured to hold a separate volume of liquid sample or reagent, and has a generally flat bottom wall except for the anti-vacuum feature. In accordance with one embodiment, the upper surface of the bottom wall includes multiple anti-vacuum channels exposed upwardly toward the volume in which liquid sample or reagent is held in the well. The anti-vacuum channels provide a fluid accessible void underneath the orifice of a pipette tip even if the pipette tip engages the bottom wall of the well, for example in the event that a pipette tip is mismounted in an automated system or an automated system lowers the head too far. In one embodiment shown in the drawings, the microplate has a matrix of <NUM> wells arranged in an 8x12 array, and a grouping of anti-vacuum channels is located on the bottom wall of each well with a center point for the grouping spaced <NUM> from the center point of groupings in adjacent wells. In another embodiment shown in the drawings, the well plate includes a matrix of <NUM> wells in a 16x24 array, with a grouping of anti-vacuum channels in each well having center points spaced in <NUM>. In either case it is desirable that channels extend to or near the well side walls. The specific configuration and dimensions of the anti-vacuum channels and groupings of channels can be the same as described above with respect to the reservoir liners and used in the liner reservoir and microtube. Microplates are typically made of polystyrene. The microplate is made of polystyrene or polypropylene, and is corona or otherwise treated treated so that the surface tension of the bottom walls of the wells is greater than or equal to <NUM> dynes.

In the above embodiments, the anti-vacuum feature has been described as groupings of channels on the upper surface of a bottom wall of a pipetting container. In a non-claimed embodiment, the anti-vacuum feature can take other forms, however, such as the use of ribs extending upward from the upper surface of a bottom wall of a pipetting container. The use of anti-vacuum channels or ribs on the bottom well of the laboratory container provides a fluid accessible void even if a pipette tip engages the bottom wall of the container. This means that the pipette tip will not cause a vacuum within the tip while the pipette is aspirating. It also means that, as a practical matter, tips can be placed closer to the bottom wall of the container and/or engage the bottom wall of the container when doing so without the anti-vacuum feature would more likely cause vacuum engagement. In turn, with the ability to move the pipette tip orifice very close to or into engagement with the bottom wall of the container, the pipetting system is able to withdraw liquid from the container with significantly less residual volume. In addition, without being limited to a theory of operation, it is believed that the hydrophilic nature of the corona treated surface causes liquid on the surface to self level, while the channels provide surface tension features that accumulate liquid on the surface. The result is that the liquid draws naturally from the surface between the groupings of channels and forms segregated pools in and above the groupings of channels, as the liquid level is drawn down. This phenomenon effectively lowers the minimum working volume for reliable pipetting. This is particularly important for expensive, scarce or small volume samples or reagents. Accordingly, the use of channels has proven to be more effective than the use of ribs. Another advantage of using channels, is that additional channels can be added to fluid dynamically connect adjacent groupings of channels. The capillary action of the channels facilitates even distribution of liquid throughout the area of the connected channels, which further can promote lower minimum working volume.

Other features and advantages of the invention may be apparent to those skilled in the art upon reviewing the drawings and the following description thereof.

<FIG> illustrate a laboratory reservoir kit <NUM> that is constructed in accordance with a first exemplary embodiment of the invention. The kit <NUM> includes a reservoir base <NUM> and a disposable liner <NUM>. The kit <NUM> is designed to hold liquid sample or liquid reagent in disposable liner <NUM> for pipetting with a hand-held pipette using disposable pipette tips, when the disposable liner <NUM> is placed within the reusable reservoir base <NUM> as shown for example in <FIG>. The kit <NUM> is designed to hold up to <NUM> of liquid sample or reagent, although the capacity of the liner <NUM> is sufficient to handle overfilling.

The reservoir base <NUM> contains a basin <NUM> into which the disposable liner <NUM> is placed. The contour of the disposable liner <NUM> generally follows the shape and contour of the basin <NUM> of the reusable base <NUM>, except for a transverse wall <NUM> in the liner <NUM> which is discussed in more detail below. Outer sidewalls <NUM> and end walls <NUM> on the reusable base <NUM> provide support for the reservoir base <NUM> and its basin <NUM> on flat surfaces such as the laboratory bench top. While the reservoir base <NUM> can be made from a variety of materials, it is preferred that the base <NUM> be made of relatively rigid injection molded plastic having an opaque color, such as white ABS. It is preferred that the surface of the basin <NUM> have a satin finish. On the other hand, as mentioned above, it is preferred that the disposable liner <NUM> be made of clear transparent plastic with at least a portion of the surface being polished, such as clear injection molded polystyrene or polypropylene having a thickness of approximately <NUM> mils. The polished or shiny surface of the clear liner, in contrast to the satin finish on the opaque colored basin <NUM> in the base <NUM>, renders it more conspicuous to laboratory workers whether or not the transparent liner <NUM> is present within the reservoir base <NUM>. Injection molding is the preferred method for the liners <NUM> because it is desirable for the liner thickness to be constant throughout. It should be recognized, however, that other manufacturing means and thickness specifications may be possible for both the disposable liners and the reusable base <NUM>.

Referring now in particular to <FIG> and <FIG>, the basin <NUM> in the reusable base <NUM> includes a narrow longitudinal trough <NUM>, <FIG> extending along its bottom surface <NUM>. The disposable liner <NUM> also includes a basin <NUM> and a narrow longitudinal trough <NUM> divided into two sections which extend between the transverse wall <NUM> and the respective end walls of the disposable liner <NUM>. Referring briefly to <FIG> and <FIG>, the trough <NUM> in the disposable liner reduces the amount of dead volume in the reservoir liner <NUM>. <FIG> and <FIG> show a pipette tip <NUM> accessing liquid <NUM> contained in the trough <NUM> of the liner <NUM>. Referring again to <FIG>, the basin <NUM> in the reusable base <NUM> includes a pair of end walls <NUM> and a pair of longitudinal sidewalls <NUM>. The basin <NUM> also includes longitudinal steps <NUM>, <FIG>, each extending longitudinally along the respective side of the trough <NUM> and connecting the trough <NUM> to the respective sidewall <NUM> of the base <NUM>. The use of the steps <NUM> allows the basin <NUM> to widen substantially over a very short depth in order to accommodate greater volumes, yet also allows for the presence of the narrow longitudinal trough <NUM> to reduce dead volume when the last vestiges of liquid are being aspirated. The disposable liner <NUM> has a matching configuration, with exception of the transverse wall <NUM> and divided basin <NUM>. The liner <NUM> includes end walls <NUM> and longitudinal sidewalls <NUM>. It also has sections of longitudinal steps <NUM> spanning between the longitudinal sidewalls <NUM> and a respective section of the trough <NUM> in the liner <NUM>. The longitudinal steps <NUM> have a slight downward slope towards the centerline of the trough <NUM>.

The reusable reservoir base <NUM> has an upper rim <NUM>, <FIG>, extending around the circumference of the top of the basin <NUM>. Desirably, a raised lip <NUM> extends upward from the rim <NUM> substantially around the entire circumference of the upper rim <NUM> except for locations along opposed center portions of the longitudinal sidewalls <NUM> of the base <NUM>. The base <NUM> includes molded indentations <NUM> at these locations, which allows the user to conveniently grasp the disposable liner <NUM> to lift the liner <NUM> from the base <NUM>.

The disposable liner <NUM> includes a peripheral flange <NUM> that extends outwardly from the upper end of the basin <NUM> defined by the sidewalls <NUM> and end walls <NUM> of the disposable liner <NUM>. The peripheral flange <NUM> of the disposable liner <NUM> rests on the upper rim <NUM> of the base <NUM> when the disposable liner <NUM> is placed within the base <NUM>. The liner <NUM> can hang within the base <NUM> so that there is a slight clearance between the basin <NUM> in the base <NUM> and the disposable liner <NUM>.

The dimensions for the disposable liner <NUM> are selected in order to provide ample volume for <NUM> of liquid sample or reagent, as well as provide a longitudinal trough length sufficient to accommodate conventional <NUM>-channel and <NUM>-channel handheld pipettes, e.g., at least <NUM>.

One sidewall <NUM> of the basin <NUM> in the reusable base <NUM> contains liquid volume graduation marks <NUM>. The liquid volume graduation marks <NUM> are preferably printed onto the sidewall <NUM>, using pad printing or any other suitable process. The liquid volume graduation marks <NUM> on the sidewall <NUM> can be seen by the user through the clear, transparent liner <NUM> when the liner <NUM> is placed in the base <NUM>. <FIG> shows the liner <NUM> placed in the base <NUM>, and illustrates that the liquid volume graduation marks (<NUM>) on the basin sidewall of the base <NUM> can be viewed through the transparent plastic liner <NUM>. The reference number (<NUM>) for the liquid graduation marks has been placed in parenthesis in the figures to indicate that the marks are actually on the opaque surface of the base <NUM> underlying the clear transparent liner <NUM>. Likewise, reference numbers (<NUM>) and (<NUM>) indicating the side and end walls of the basin <NUM> in the base <NUM> underlying the transparent liner in these figures have been placed in parenthesis as well. Further, as shown in <FIG> and <FIG>, volume indicators (<NUM>) are printed on the basin sidewall (<NUM>) of the base <NUM>. The reference number (<NUM>) are again placed in parenthesis in these figures to indicate that the volume amount indicators (<NUM>) are actually printed on the basin sidewall <NUM> of the base <NUM>, but can be seen through the clear, transparent liner <NUM>. The volume indicators (<NUM>) for the divided basin in the liner <NUM> are specific for the respective side to the wall <NUM> on the liner <NUM>, and are accumulated above the wall <NUM>. A <NUM> kit <NUM> may include the values (<NUM>) of <NUM>, <NUM> for graduation marks corresponding to one side of the wall <NUM> on the liner <NUM> and <NUM>, <NUM> next to graduation marks for the other side of the wall <NUM>, assuming that that wall <NUM> divides the liner basin so that one side has half the volume of the other side. For locations corresponding to above the transverse wall <NUM> on the liner <NUM>, the <NUM> kit <NUM> may include the value (<NUM>) of <NUM> for graduation mark. Since the kit <NUM> is intended to be used with the disposable liner <NUM> set in place within the base <NUM>, the location of the graduation marks <NUM> is calibrated with respect to the volume of liquid contained within the disposable liner <NUM> when the disposable liner is in place, not with respect to the volume of the basin <NUM> of the base <NUM>.

In fact, it is not desirable for the user to use the reusable reservoir base <NUM> as a stand-alone reservoir. The basin <NUM> in base <NUM> includes drainage openings in part to discourage the improper use of the reservoir base <NUM> as a stand alone reservoir without the use of a disposable liner <NUM>. In addition, these holes prevent sticking of the disposable liners <NUM> to the reservoir base <NUM> should some liquid become located between the two surfaces.

Referring now in particular to <FIG>, when liquid <NUM> is contained within the disposable liner <NUM>, liquid volume graduation marks <NUM> below the surface <NUM> of the liquid <NUM> may be blocked from view to the user, depending on the user's angle of perspective. Arrows <NUM> and <NUM> in <FIG> illustrate this concept. Light traveling along the path indicated by arrow <NUM> is reflected from the top surface <NUM> of the liquid <NUM> (e.g., water) and thus prevents the user from seeing graduation marks <NUM> below the top surface <NUM> of the water <NUM>. On the other hand, the user can view the graduation marks <NUM> above the surface <NUM> of the water as depicted by arrow <NUM>. Thus, it is preferred that the volume indicators <NUM> on the basin sidewall <NUM> of the base <NUM> be printed at or above the calibrated liquid volume graduation marks <NUM> to which they are associated. This makes the liquid level easier to read.

<FIG> and <FIG> illustrate the liquid in the liner <NUM> drawn down to a low liquid level. In accordance with the invention, the pipette tip <NUM> is pressed down and engaged against the liner <NUM> in the liner trough <NUM>. The trough <NUM> desirably has a circular or rounded cross section as illustrated in <FIG> and <FIG> to facilitate the use of groupings <NUM> of anti-vacuum channels on the upper surface of the liner trough <NUM>. Referring now to <FIG> and <FIG>, a plurality of groupings <NUM> of anti-vacuum channels <NUM> are located on the upper surface of the liner trough <NUM>, and are exposed upwardly into the liner basin <NUM> in which liquid sample or liquid reagent is held for pipetting. The groupings <NUM> are disposed linearly along the liner trough <NUM> and run along the low point of the trough <NUM>. Each channel grouping <NUM> includes perpendicular intersecting channels <NUM>, <NUM> which intersect at a center point <NUM>, see <FIG>. A circular channel <NUM> having a center at the center point <NUM> intersects the perpendicular channels <NUM>, <NUM>. In this embodiment, the center points <NUM> are spaced at <NUM>, corresponding to one half of the distance of the spacing between SBS formatted <NUM> pipette tips. In addition, one set of channels <NUM> lies along the longitudinal middle of the trough <NUM>, with the other set of perpendicular channels lying transverse. These longitudinal channels <NUM> extend to the adjacent groupings <NUM> in order to fluid dynamically connect the adjacent groupings <NUM> and channel fluids between adjacent groupings <NUM>. In order to minimize residual dead volume, it is desirable to make the liner <NUM> of molded polystyrene or polypropylene and corona treat or otherwise treat the surface rendering it more hydrophilic, thereby providing a surface on which the liquid tends to spread rather than bead. Over treatment can be counterproductive if it causes some liquid to spread up the sidewall of the trough <NUM>. It is preferred that the treatment render the surface tension equal or greater than <NUM> dynes, which is the surface tension of natural water.

The liner <NUM> is made of molded polystyrene or polypropylene, corona treated to render the surface tension equal or greater than <NUM> dynes. As mentioned, polypropylene is not a stiff as polystyrene but the polypropylene provides more chemical resistance which may be needed in certain applications.

The width of the channels <NUM>, <NUM>, <NUM> is desirably about <NUM> +/- <NUM>, except the channel must include a draft angle for molding purposes. Since the bottom of trough <NUM> is rounded, this means that the channels near the sidewall are wider than those along the centerline.

<FIG> shows an exemplary pipette tip <NUM> engaging the exposed surface of the liner trough <NUM> with anti-vacuum channels <NUM> below the tip orifice. With the anti-vacuum channels and the fluid accessible voids underneath the pipette tip orifices, aspiration can occur without causing a vacuum in the pipette tip even if the tip engages the surface of the liner trough. Further, with the hydrophilic surface and connected channels in the trough, even fluid distribution along the trough is facilitated at low liquid levels, which results in a lower minimum working volume for reliable pipetting with a multi-channel pipette.

Referring now to <FIG>, a laboratory reagent kit <NUM> constructed in accordance with the second embodiment of the invention is illustrated. Referring to <FIG>, the kit <NUM> includes a reservoir base <NUM> and a disposable liner <NUM>. <FIG> also show an exemplary pipette tip <NUM>. The kit <NUM> is designed to hold liquid sample or liquid reagent in the disposable liner <NUM> when the disposable liner <NUM> is placed within the reusable reservoir base <NUM> as shown for example in <FIG>. The disposable liner <NUM> is configured for a <NUM> pipetting head, has an array of <NUM> by <NUM> groupings <NUM> of anti-vacuum channels, and sized to hold up to <NUM>. Each grouping <NUM> of channels is located in a recess <NUM> on the bottom wall <NUM> of the liner <NUM>. The basin in the reservoir base <NUM> supports the disposable liner <NUM>. Outer side walls <NUM> and end walls <NUM> on the reusable base <NUM> provide support for the reservoir base <NUM> on flat surfaces such as a laboratory bench top. While the reservoir base <NUM> can be made of a variety of materials, it is preferred that the base <NUM> be made of relatively rigid injection molded plastic having an opaque color such as white ABS. It is preferred that the surface of the inner basin of the base <NUM> have a satin finish. On the other hand, it is preferred that the disposable liner <NUM> be made of clear transparent plastic and have a polished surface, such as clear injection molded polystyrene or polypropylene having a thickness of approximately <NUM>. The polished or shiny surface of the clear liner, in contrast to the satin finish on the opaque inner basin of the base <NUM>, renders the transparent liner <NUM> more conspicuous to laboratory workers trying to determine whether or not it is present within the reservoir base <NUM>. Injection molding is the preferred method to manufacture the disposable liner <NUM> because it is desirable for the liner thickness to be constant throughout. It should be recognized, however, that other manufacturing methods and thickness specifications may be possible for both the disposable liner <NUM> and the reusable base <NUM>. The inner basin of the reusable base <NUM> is rectangular and extends between the bottoms of the inside surfaces of the end walls <NUM> and the side walls <NUM>. The bottom wall <NUM> of the basin in the reusable base <NUM> is flat. Referring to <FIG> and <FIG>, the disposable liner <NUM> is configured to fit in the base <NUM> so that the bottom wall <NUM>, the end walls <NUM> and the longitudinal side walls <NUM> of the base <NUM> support the disposable liner <NUM> with the bottom wall <NUM> of the liner <NUM> sitting on the bottom wall <NUM> of the reservoir base <NUM>.

The bottom flange <NUM> on the base <NUM> has outside wall dimensions compatible with SBS standards (namely ANSI/SLAS <NUM>-<NUM>: Microplates - Bottom Outside Flange Dimensions). Having SBS compatible outside wall dimensions means that the base <NUM> will fit into platform nests for liquid handling systems having a <NUM> pipetting head, and be in alignment so that each of the pipette tips aligns at least generally with one of the groupings of anti-vacuum channels <NUM>. Since the liner <NUM> is made for a <NUM> pipetting head, the distance between the center points <NUM> for adjacent groupings of channels <NUM> in the respective recesses <NUM> is <NUM>.

Reference number (<NUM>) depicts volume liquid graduation marks which as in the previous embodiment are printed on the side wall of the base <NUM> so that they can be viewed through the liner <NUM> made from a clear transparent material such as molded polystyrene or polypropylene. The disposable liner <NUM> in this embodiment, as mentioned, has a bottom wall <NUM> patterned with recesses <NUM>. A window <NUM> is provided in the front side wall <NUM> of the base <NUM> to facilitate viewing of liquid in the liner <NUM>. Additional windows can be provided if desired. <FIG> shows the disposable liner <NUM> set into the reusable base <NUM>.

Referring to <FIG>, the groupings of anti-vacuum channels <NUM> on the bottom wall <NUM> of the liner <NUM> have a first pair of perpendicularly intersecting channels <NUM> and a second pair of perpendicular channels <NUM> which are rotated <NUM> degrees from the first pair. The second pair of perpendicular channels <NUM> are interrupted in the vicinity of at the center point <NUM> of the intersection of the first pair of channels <NUM>, which creates an irregularly shaped pedestals at the height of the upper surface of the bottom wall <NUM> between the channels. Allowing the second pair of channels <NUM> to continue through the center point <NUM> would create an air space around the center point <NUM> having too great of a diameter to obstruct continued downward movement of the lower distal end of the smallest sized pipette tip that the disposable liner <NUM> is designed to be used with. For the <NUM> pipetting head, the channels <NUM>, <NUM> in <FIG> may optimally be a width of <NUM> ± <NUM> and a depth of <NUM> ± <NUM>, for example. The configuration of the channel groupings <NUM> in <FIG> is an alternative configuration to that shown in the first embodiment.

Referring now to <FIG>, the bottom wall <NUM> of the liner <NUM> is patterned with recesses <NUM> in order to reduce residual liquid waste. Referring in particularly to <FIG>, each grouping of channels <NUM> is located within a recess <NUM> which preferably has the curvature of a partial sphere. Each recess <NUM> is separated from adjacent recesses by a linear ridge <NUM> as shown in <FIG> (and also shown from above in <FIG>). Since the liner <NUM> is made for a <NUM> pipetting head, the distance between the center points <NUM> for adjacent groupings of channels <NUM> in the respective recesses <NUM> is <NUM>. The low points <NUM> of the respective recesses <NUM> are located at the center point <NUM> of the respective recess <NUM> and at the center point <NUM> for the respective channel grouping <NUM>. The low point <NUM> for all recesses in the liner <NUM> should reside in a common plane so that the bottom wall <NUM>, while patterned or dimpled, sits generally level on the straight bottom wall <NUM> of the base <NUM>. The bottom of the pipette tip <NUM> is shown pressing against the pedestals <NUM> so that part of the channels <NUM>, <NUM> are located at least partially below the tip orifice. In this way, no vacuum is created when the pipette is operated to aspirate liquid into the pipette tip <NUM>.

<FIG> show a disposable reservoir liner <NUM> constructed in accordance with another embodiment of the invention. Referring now to <FIG>, the liner <NUM> contains groupings <NUM> of anti-vacuum channels designed to accommodate both a <NUM> pipetting head and a <NUM> pipetting head. In this embodiment, some of the anti-vacuum channels are shared between groupings <NUM> for the <NUM> pipetting head and the groupings <NUM> for the <NUM> pipetting head, see <FIG>. The anti-vacuum channels <NUM> extend beyond the area in which they are expected to be used for pipette tips on a <NUM> head and are part of the groupings <NUM> of anti-vacuum channels used for a <NUM> head. The <NUM> head groupings <NUM> as depicted is <FIG> include horizontal and vertical channels and diagonal channels in addition to a circular channel. The bottom wall <NUM> of the liner <NUM> in this embodiment is flat except for the channels <NUM> on the upper surface of the bottom wall <NUM>. The distance between adjacent center points for <NUM> head channels groupings is <NUM>. The distance between center points for adjacent <NUM> head groupings is <NUM>. Desirably, the width of the channels is <NUM> +/- <NUM>. Groupings of anti-vacuum channels with alternative configurations can be substituted depending on the intended use of the liner <NUM>. In addition, the channel grouping configuration shown in <FIG> can be used in other embodiments, such as that shown in <FIG>.

A removable baffle <NUM>, or splashguard, is set within the basin of the liner <NUM>. The splashguard <NUM> shown in <FIG> includes a plurality of upstanding walls <NUM> and <NUM>. Upstanding walls <NUM> are located between adjacent rows of the groupings <NUM> of anti-vacuum channels. In the embodiment shown in <FIG>, there are eleven (<NUM>) walls <NUM> between the rows of groupings <NUM> of anti-vacuum channels. There is one upstanding wall <NUM> that is perpendicular to the upstanding walls <NUM> located between the rows of groupings <NUM> of anti-vacuum channels. The upstanding walls <NUM> and <NUM> are molded together as a single component that is removable from the liner <NUM>. As shown in <FIG>, the upstanding walls <NUM> extend from the bottom wall <NUM> upward vertically, but there is no seal at the bottom of the upstanding walls <NUM> which is depicted by reference number <NUM>. As mentioned, the bottom wall <NUM> is flat, not patterned as shown in <FIG>. The upstanding walls <NUM> extend between sidewalls <NUM> and <NUM> of the liner <NUM>, but similarly do not form a seal at the point of engagement with the sidewalls <NUM>, <NUM>. The upstanding wall <NUM> extends between end walls <NUM>, and likewise does not form a seal at the end walls <NUM>. The splashguard <NUM> can contain more upstanding walls <NUM> extending between the end walls <NUM>, and can also include less upstanding walls <NUM> extending between the sidewalls <NUM>, than is shown in <FIG>. In accordance with the invention, however, it is desirable that the walls <NUM>, <NUM> be located between adjacent rows or columns of groupings <NUM> of anti-vacuum channels.

<FIG> show another embodiment of the invention in which a disposable liner <NUM> includes upstanding walls <NUM> as an integral component, such that the reservoir liner <NUM> in effect contains multiple separate basins. Referring to <FIG>, the upstanding walls <NUM> are integrally molded with the flat bottom wall <NUM> of the liner so that the bottom <NUM> of the respective wall <NUM> is completely sealed with the bottom wall <NUM>. In this example, there are eleven (<NUM>) upstanding walls <NUM> extending between sidewalls <NUM>. The intersection between the upstanding walls <NUM> and the sidewalls <NUM> is also integrally molded to form a seal. The disposable liner <NUM> therefore contains twelve (<NUM>) separate basins. The floor of each basin <NUM> desirable includes a row of groupings <NUM> of anti-vacuum channels. Each grouping <NUM> has the small configuration as shown in <FIG> and described above. The walls <NUM> are placed between adjacent rows of groupings <NUM>. A disposable liner can be made to include less than eleven (<NUM>) walls, and can also include one or more walls extending between end walls <NUM>, i.e. in a direction perpendicular to the walls <NUM> shown in <FIG>. In all cases, it is important that the walls do not interfere with the location of an array of pipette tips on a <NUM> and/or <NUM> pipetting head. The groupings <NUM> of anti-vacuum channels in the liner <NUM> shown in <FIG> are designed to accommodate both <NUM> pipetting heads and <NUM> pipetting heads. Groupings of anti-vacuum channels with alternative configurations can be substituted depending on the intended use of the liner <NUM>.

The liners in the embodiments shown in <FIG> are made of polystyrene or polypropylene and corona treated in order to make the bottom wall with anti-vacuum channels more hydrophilic; e.g. a surface tension of greater then or equal to <NUM> dynes which is the surface tension of natural water. In addition, it may be desirable to connect the groupings of channels with intervening channels. As mentioned above, it is believed that the hydrophilic nature of the corona treated surface causes liquid on the surface to self level, while the channels provide surface tension features that accumulate liquid on the surface. The result is that the liquid draws naturally from the surface between the groupings of channels and forms segregated pools in and above the groupings of channels as the liquid level is drawn down. This phenomenon, as mentioned, effectively lowers the minimum working volume for reliable pipetting.

<FIG> are directed to another embodiment of the invention in which a laboratory reservoir <NUM>, without a disposable lining, includes anti-vacuum channels <NUM> exposed upwardly towards the volume in which liquid sample or liquid reagent is held. The reservoir <NUM> in <FIG> includes a basin <NUM> with optional walls <NUM> extending between sidewalls <NUM> of the basin <NUM>. The upstanding walls <NUM> are sealed at the bottom <NUM> along the bottom wall <NUM> of the reservoir and are also sealed at the points where the upstanding walls <NUM> intersect with the respective sidewalls <NUM>. There are eleven (<NUM>) upstanding walls <NUM> separating the reservoir basin <NUM> into twelve (<NUM>) separated volumes. These upstanding walls <NUM> are optional and the other described aspects of the invention can be implemented whether the upstanding walls <NUM> are present or not. In addition, the reservoir <NUM> can be designed with one or more upstanding walls extending between end walls <NUM>. Referring in particular to <FIG>, the reservoir <NUM> includes groupings <NUM> of anti-vacuum channels which are located in an array of rows and columns appropriate for both SBS formatted <NUM> pipetting heads and <NUM> pipetting heads.

In the version of the reservoir <NUM> shown in <FIG>, the bottom wall <NUM> is flat, except for the anti-vacuum channels. As an alternative to groupings of anti-vacuum channels <NUM> as depicted in <FIG> and <FIG>, the entire upwardly facing surface of the bottom wall <NUM> can include anti-vacuum channels. Desirably, however, separated groups <NUM> of anti-vacuum channels are molded into the bottom wall <NUM>, or the groupings can be connected with intervening channels. The configuration of the groupings <NUM> is desirably the same or similar to that described above with respect to the reservoir liners and particularly shown in <FIG>. The reservoir <NUM> is made of polystyrene or polypropylene, and corona treated or otherwise treated in order make the bottom wall <NUM> with the anti-vacuum channels more hydrophilic than before treatment; providing a surface tension of greater than or equal to the surface tension of natural water, <NUM> dynes, for the same reasons as discussed above with respect to the other embodiments.

Whether or not a reservoir constructed in accordance with the invention includes the optional upstanding walls <NUM>, it may be desirable to pattern the bottom wall <NUM> with round recesses in order to reduce liquid hang-up, as described above in <FIG> but with respect to the bottom wall of a liner. For a reservoir having a patterned bottom wall designed to be used with a <NUM> pipetting head, the bottom wall <NUM> of the reservoir <NUM> would include an array of <NUM> by <NUM> groupings of anti-vacuum channels each having a center point with <NUM> spacing. The anti-vacuum channels would not include groupings for <NUM> tips at a <NUM> spacing. Each grouping of channels is located within a recess, and to the extent that adjacent groupings are not separated by a wall, the recesses are separated by linear ridge similar to that described above with respect to <FIG>. The low points of the respective recesses are desirably located at the center point of the groupings of anti-vacuum channels, and also reside in a common plane, so that the bottom wall, while patterned or dimpled, sits generally level. For a reservoir having a patterned or dimpled bottom wall and designed for use with a <NUM> pipetting head, groupings of anti-vacuum channels are spaced at <NUM> and are located in recesses spaced at <NUM> apart.

<FIG> illustrate a laboratory microtube <NUM> having anti-vacuum channels <NUM> on the bottom wall <NUM> of the microtube in accordance with another aspect of the invention. The microtube <NUM> includes a receptacle <NUM> for holding liquid reagents or samples. The receptacle <NUM> has cylindrical sidewalls and a bottom wall <NUM> which is normally flat, or at least a portion of it is flat, except for the channels <NUM>. Although not shown in <FIG>, a beveled portion exists in some microtubes and extends between the cylindrical sidewall <NUM> and the flat portion <NUM> of the bottom wall. The anti-vacuum channels <NUM> are located on the flat portion of the bottom wall <NUM>. The mircotube <NUM> also includes a cap <NUM> for closing the microtube. The cap <NUM> is shown attached to the microtube <NUM> but need not be attached. The microtube <NUM> is molded from polypropylene. The microtube is corona treated so that the bottom wall <NUM> has increased wettability compared to the bottom wall prior to corona treating. In <FIG>, it is desired that the channels have a width of <NUM> ± <NUM>. <NUM> and have a depth of <NUM> ± <NUM>. The pattern of anti-vacuum channels shown on <FIG> includes a first pair of perpendicular intersecting channels <NUM> with the intersection defining a center point <NUM> and a second pair of perpendicular channels <NUM> rotated <NUM>° from the first pair <NUM>. The second pair <NUM> of channels are aligned to intersect at the center point <NUM> but are interrupted in the vicinity of the center point <NUM>. In addition, an inner circular channel <NUM> and an outer circular channel <NUM> are provided both intersecting with each of the channels of the first <NUM> and second <NUM> pairs. Additional channels <NUM> extend from the inner circular channel <NUM> through the outer circular channel <NUM> and beyond towards the cylindrical wall <NUM>. The channel configuration covers essentially the entire bottom wall, which not only provides the anti-vacuum feature over the entire area of the bottom wall to facilitate reliable use with a hand-held pipette without the risk of vacuum engagement but also helps to draw liquid towards the pipette tip orifice when aspirating the final amount of liquid from the tube because of the capillary action of the channels. Other rib or channel configurations may be suitable for implementing the invention in a microtube as well.

While the bottom wall <NUM> is flat in the embodiment of the microtube <NUM> shown in <FIG>, it is also possible for the microtube to have a curved bottom. In this case, it is desired that the curved bottom be spherical with the low point of the sphere aligning with the center point of the anti-vacuum channels or ribs.

<FIG> show a PCR tube <NUM> having a group of anti-vacuum channels <NUM> on a bottom wall <NUM>. The PCR tube <NUM> includes a tube body <NUM> and a cap <NUM>, which are made of polypropylene as is typical in the art. As with the other embodiments, the tube is corona or otherwise treated so the surface tension is greater then or equal to the surface tension of natural water of <NUM> dynes. The tube body <NUM> has an upper cylindrical wall <NUM> and a lower tapered wall <NUM>. The bottom wall <NUM> located at the bottom of the tapered wall <NUM> and is flat in <FIG> except for the anti-vacuum channels <NUM>, although in some PCR tubes the bottom wall may be curved. The grouping <NUM> of anti-vacuum channels includes perpendicular channels <NUM>, <NUM> which insect at a center point <NUM>. A circular channel <NUM> intersects the perpendicular channels <NUM>, <NUM>. The perpendicular channels <NUM>, <NUM> extend beyond the flat portion <NUM> of the bottom wall and slightly up a transition to the lower tapered wall <NUM>. The channels in this embodiment have a width <NUM> +/- <NUM> when located on the flat portion of the bottom wall. Channel width is not as important along the sidewall because the pipette tip cannot bottom out on the sidewall. Nevertheless, the channels must have an appropriate draft angle to facilitate reliable molding during production. It is contemplated that a similar channels configuration can be implemented in a PCR strip or PCR plate having several receptacles each individually similar to the channel configuration of the PCR tube shown in <FIG>.

<FIG> show the use of the anti-vacuum channels in microplates. <FIG> show a <NUM> well microplate <NUM> having anti-vacuum channels <NUM> on the bottom wall <NUM> in each well <NUM>. <FIG> show a <NUM> microplate <NUM> having anti-vacuum ribs <NUM> on the bottom wall <NUM> of each well <NUM>. Both the <NUM> well microplate <NUM> and the <NUM> well microplate <NUM> have sidewalls <NUM>, <NUM> and end walls <NUM>, <NUM>, as well as a bottom, outer wall flange <NUM>, <NUM>, dimensioned to fit in nests configured to hold SBS-formatted microplates. The <NUM> well microplate <NUM> includes <NUM> separate wells arranged in <NUM> columns and <NUM> rows with each well <NUM> being configured to hold a volume of liquid sample or reagent. The center point for each of the wells is spaced <NUM> from the center point of adjacent wells, and the center point for the anti-vacuum channels <NUM> in the respective wells <NUM> is also centered at the center point of the wells <NUM>. For the <NUM> well microplate <NUM>, the anti-vacuum channels desirably have a width of <NUM> +/- <NUM> and have a depth of <NUM> +/- <NUM>. Each well includes one grouping of anti-vacuum channels. The grouping <NUM> desirably includes a first pair of perpendicularly intersecting channels <NUM>, and a second pair perpendicularly intersecting channels <NUM> from the first pair <NUM>. The second pair <NUM> intersect at a center point, and the first pair are interrupted as they would otherwise pass through the center point. An inside circular channel <NUM> and an outside circular channel <NUM> intersect the channels of the first <NUM> and second <NUM> pairs of channels. As with other embodiments, the microplates in <FIG> are made of polystyrene or polypropylene and corona treated or otherwise treated to increase wettability for similar reasons as explained above.

While <FIG> show a <NUM> well plate where the bottom wall <NUM> of the wells is flat except for the channels, the wells may also be curved instead of flat with the center point of the grouping of anti-vacuum channels being aligned with the low point of the curved bottom wall and also spaced <NUM> from adjacent channel groupings in other wells.

Referring to <FIG>, the <NUM> well microplate <NUM> includes <NUM> wells <NUM> in each row and <NUM> wells in each column, and a grouping of anti-vacuum channels <NUM> on the bottom wall <NUM> in each well with the center point of the grouping <NUM> being spaced <NUM> from the center point of groupings in adjacent wells <NUM>. In this embodiment, the desired channel width is <NUM> +/-<NUM>. The configuration of the group of anti-vacuum channels needs to be slightly different in order to fit in the square wells <NUM> in the <NUM> well microplate <NUM>. As shown for example in <FIG>, the wells <NUM> are square and the grouping <NUM> of anti-vacuum channels <NUM> includes a first pair of perpendicular channels <NUM> that intersect at the center point, and a second pair of perpendicular channels <NUM> rotated <NUM> degrees. As in other embodiments, the channels of the second pair are interrupted in the vicinity of the center point. A circular channel <NUM> intersects the first <NUM> and second <NUM> pairs of channels.

The use of anti-vacuum channels on the bottom wall of various pipetting containers has been described in connection reservoirs, reservoir liners, microplates, microtubes and PCR tubes, but may be useful with other pipetting containers or receptacles as well. In some applications, anti-vacuum ribs may be suitable for use on the bottom wall of the pipetting containers.

Claim 1:
A pipetting container (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
one or more receptacles for holding liquid reagents or samples for pipetting, each receptacle having a bottom wall, and one or more groups (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of interconnected anti-vacuum channels on an upper surface of the bottom wall and exposed upwardly into the receptacle in which liquid sample or liquid reagent is held for pipetting; characterized in that the receptacle is made from one of molded polystyrene and molded polypropylene and is corona treated or otherwise treated so that the upper surface of the bottom wall of the receptacle has increased wettability compared to the upper surface of the bottom wall before treating and the measured surface tension of the upper surface of the bottom wall of the receptacle is greater than or equal to about <NUM> dynes/cm for natural water.