Patent Publication Number: US-2023158509-A1

Title: Biodegradable pipette tip rack

Description:
FIELD OF THE INVENTION 
     The invention relates to pipette tip racks, and particularly to biodegradable, compostable, and recyclable racks for arrays of consumable air displacement pipette tips. 
     BACKGROUND OF THE INVENTION 
     Air displacement pipettes, in which a simple handheld pipette moves a piston through an air-tight seal to aspirate or dispense liquid in a disposable pipette tip, are commonly found in scientific laboratories and manufacturing sites across a wide spectrum of disciplines, from medical and pharmaceutical research to genetics and forensics. Pipettes are used by workers in such laboratories and other settings to handle and dispense small quantities of liquids, from one microliter (or less in some cases) up to ten or more milliliters. In many cases, these workers perform repetitive dispensing tasks all day long, and end up handling hundreds of samples per day. And especially where multichannel pipettes are being used, the number of samples handled per day may be in the thousands. 
     To avoid cross-contamination, air displacement pipette tips are usually used once and discarded—they are treated as disposable or consumable. And because air displacement pipettes are convenient and efficient, allowing for the handling of hundreds or thousands of samples per day, handheld single and multichannel pipetting devices use very many disposable tips. A pipetting worker handling many samples needs a convenient supply of replacement tips close at hand. 
     Most commercially available pipette tips are made available in injection molded plastic racks, each rack containing 96 tips in an 8×12 array. This physical configuration easily and conveniently accommodates single channel pipettes (that use a single tip at a time, selected from the  96  in a box) and multichannel pipettes in a variety of configurations (1 row×6 channels, 1×8, 1×12, 2×8, 2×12, etc.). Traditional racks are usually fabricated from a relatively rigid polymer (such as polypropylene or polycarbonate) that is robust and easily able to withstand the forces encountered in mounting tips to a single-channel or multichannel pipette. 
     A rack is usually provided in the form of a box with a lid (either hinged or removable) with tips suspended in an array of openings defined by a deck held in the box and revealed when the lid is opened. Pipette tips are generally tapered in shape, with a narrow distal end and wider proximal mount, and accordingly, the mount ends of the array of tips can be positioned above the openings in the deck while the narrow distal ends extend through the openings in the deck. History has shown that this is a convenient way of storing tips and making them available for use—a user can simply press the shaft of a pipette into a tip (or in the case of a multichannel pipette, press the row or rows of nozzles into a corresponding row or rows of tips in the rack), ensure the tips are mounted by applying pressure against the rack and deck, and then simply lift the tip or tips out of the openings to use them. 
     While this tip rack design has been used throughout the world for many years, when empty, it produces incalculable amounts of persistent environmental plastic waste upon disposal. 
     When all of the tips in a rack are used, the rack is empty and is either discarded or refilled. 
     Some pipette users favor tip refill systems, and to the extent such refill systems have been successful, they have been simple and easy to use, requiring minimal extra steps. 
     One example of a successful single-use pipette tip refill system is available from Rainin Instrument, LLC, under the GREEN-PAK trademark. This product is described in U.S. Pat. No. 5,392,914, which is hereby incorporated by reference as though set forth in full. In a GREEN-PAK refill package, an array of 96 tips is held in a replacement tip wafer or plate within a thermoformed “blister” package that is sealed at one end—the end covering the narrow distal ends of the pipette tips—with a peelable, non-replaceable cover that seals the package. To refill a pipette tip rack, the GREEN-PAK refill package is opened by peeling the cover off, the array of tips is positioned carefully over the corresponding supportive deck or grid in the empty tip rack, and the tips (and the tip wafer) are pushed out of the GREEN-PAK package by deforming the thermoformed blister package. The wafer is then snapped into place and held by retainers in the deck or grid. The GREEN-PAK blister package thermoform is thin and flexible and uses minimal material; provides protection for the pipette tips during shipment and storage. The GREEN-PAK blister is also made from a more recyclable plastic type. However, it is not possible to mount tips directly from a GREEN-PAK package, not only because the tips are inverted (with the narrow ends facing out), but because the package is too flexible to withstand the pressure required to mount tips onto a pipette shaft. The GREEN-PAK refill package, while convenient, still requires a rack-loading step and extra handling. 
     The SPACESAVER tip refill package from Rainin Instrument, LLC, makes even more efficient use of materials and space. A SPACESAVER tip refill package includes eight or ten refills (768 or 960 tips) in approximately the space occupied by 1-2 traditional pipette tip racks or a single GREEN-PAK refill. The original SPACESAVER system is described in U.S. Pat. No. 5,441,702, which is hereby incorporated by reference as though set forth in full. The original SPACESAVER refill module included the aforementioned rack and a thermoformed sleeve holding, in total, eight or ten nested arrays of tips. A re-designed SPACESAVER has eliminated the rack but retains the thermoformed sleeve. To fill an empty rack, a user positions the sleeve over the rack, aligns the tips, and pushes down on the nested arrays; the bottom array and corresponding tip deck snaps into place within the rack and the others slide down one level and can be removed and stored for future use. The SPACESAVER tip refill system provides good storage efficiency and uses minimal materials, but does still require a loading step and once opened, sterility cannot be maintained. Moreover, because the SPACESAVER system employs nested tips, it is not suitable for refilling racks with tips that include aerosol resistant filters. 
     Various other tip refill systems are available from many pipette tip manufacturers. They are all relatively convenient to use, but are all less convenient than simply opening and using a new rack of pipette tips when needed. Even with the great improvements that have been made in tip refill systems over the past decades, many users still prefer single-use racks to avoid the hassle of refills. Some users may also have concerns over the cleanliness of the rack itself, and not just the tips. Ultimately, the empty racks require disposal and, in some manner, entry into the environment. Using single-use racks minimizes handling requirements (and the distractions arising therefrom), ensures a fresh rack is always available, and maintains sterility better than multi-pack refill systems. However, single-use racks, depending upon their composition, can be more profligate in the amount of disposable plastic waste that they generate. 
     Accordingly, there is a need to reduce the environmental impact of discarded pipette tip racks, not all of which will be recycled. This need is met by the replacement of plastic rack components with those that are largely cellulose-based and hence, compostable and/or biodegradable. 
     SUMMARY OF THE INVENTION 
     Accordingly, then, a pipette tip rack according to the invention is fabricated from a natural fibrous cellulose material that much of its composition will be, to various degrees, biodegradable, compostable, or recyclable. The rack includes a shell that is formed from a molded fibrous cellulose material, holding in place and storing within a lightweight molded plastic tip deck that accommodates an array of pipette tips. The shell includes features that retain the tip deck firmly in a desired seated position, and both the tip deck, cellulose shell and additional components are advantageously configured, harmoniously integrated, and reinforced to accommodate the forces received when a user presses a pipette against one or more tips on the deck to mount the tips to the pipette. 
     In an embodiment of the invention, the molded fibrous shell includes a box-shaped body and a separate form-fitting lid. The lid is configured with a peripheral lip structure that fits securely over a corresponding lip structure on the shell. The resulting interference or friction fit between the lid and the body serves to reduce the intrusion of dust and other contaminants into the pipette tip rack when the lid is closed. 
     A rack according to the invention further includes features in the shell that hold a pipette tip deck firmly in position, and a tubular cellulose sleeve that prevents tips in the deck from tilting and abrading an interior surface of the shell; preferably, the sleeve also provides additional support and rigidity to the tip deck. 
     A pipette tip rack according to the invention may be used alone, on a flat surface such as a table or bench, or hand held, or held within a stabilizing base structure. 
     In comparison to those traditional rigid injection molded pipette tip racks, a pipette tip rack according to the invention provides considerable benefits, including: reduced plastic waste and associated environmental benefits, reduced weight, and potentially reduced manufacturing and shipping costs. Compared with single-use and multi-use refill packages, a pipette tip rack according to the invention may also have significant benefits: reduced handling and improved cleanliness and sterility. A pipette tip rack according to the invention can be sold in a pre-sterilized and shrink-wrapped condition (or otherwise protected, e.g., in flow wrap, bags, or TYVEK® packaging), ensuring contamination-free pipette tips are available at all times. A pipette tip rack according to the invention can be made available in individually wrapped packages or in multi-packs as desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features, and advantages of the invention will become apparent from the detailed description below and the accompanying drawings, in which: 
         FIG.  1    illustrates an exterior view of a pipette tip rack according to the invention; 
         FIG.  2    illustrates an empty shell of a pipette tip rack according to the invention; 
         FIG.  3    illustrates a lid for a pipette tip rack according to the invention; 
         FIG.  4    represents a shell of a pipette tip rack according to the invention, with a tip deck inserted into and held within the shell; 
         FIG.  5    represents a partial cutaway side view of an embodiment of a pipette tip rack according to the invention; 
         FIG.  6    represents a cutaway view of a portion of a tip rack according to the invention where a lid meets a shell; 
         FIG.  7    represents an exemplary paper pattern usable for a tubular sleeve in a pipette tip rack according to the invention; and 
         FIG.  8    illustrates a shell of a pipette tip rack according to the invention, with a tubular sleeve in place within the shell. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is described below, with reference to detailed illustrative embodiments. It will be apparent that a system according to the invention may be embodied in a wide variety of forms. Consequently, the specific structural and functional details disclosed herein are representative and do not limit the scope of the invention. 
     Referring initially to  FIG.  1   , a pipette tip rack  110  according to the invention is illustrated. The pipette tip rack  110  includes a generally tapered box-shaped body  112  with rounded corners and a cooperative lid  114 , each of which is fabricated from a biodegradable material such as molded cellulose fiber pulp. As used herein, the term “biodegradable” may refer to materials that are capable of being degraded (either by natural or induced conditions) over the course of time after use, and may include materials generally regarded as biodegradable, compostable (e.g., likely to break down under certain conditions of temperature and moisture), and recyclable (e.g., capable of being broken down and reused). The term “cellulose fiber” may refer to any suitable naturally derived or artificially created fibrous material, including (for example) bamboo fiber, pre- or post-consumer recycled paper fiber, bagasse (such as from sugar cane), in various combinations and proportions or blended with other materials, and either untreated or with an additive or surface treatment to improve the performance characteristics of the material. 
     As illustrated in  FIG.  2   , the shell  112  includes various features to facilitate its use as a pipette tip rack shell. The shell has a substantially flat and generally rectangular bottom surface  212 , with four side walls  214 ,  216 ,  218 , and  220  extending upward therefrom at an obtuse angle. Two of the side walls  214  and  216  are longer than the other two side walls  218  and  220 , thereby defining an interior cavity of the shell that is larger near the tops of the side walls  214 - 220  than near the bottom. This is a standard and traditional shape for a pipette tip rack shell, and in a pipette tip rack according to the invention it facilitates molding and mold release, and is well suited to receive a tip deck and an array of pipette tips as described in further detail below. 
     The shell  112  includes a plurality of ribs  222  and  224 , which as shown in  FIG.  2    are inward-facing. The ribs  222 - 224  help to rigidify the shell, preventing collapse or deformation when a pipette is used to mount tips from the pipette tip rack  10 . As illustrated in  FIG.  2   , the two longer sidewalls  214 - 216  each have three ribs  222  that extend inwardly toward the interior cavity from the respective sidewalls, and appear as depressions on an exterior surface  226  of the shell  112  and as protrusions on an interior surface  228  of the shell  112 . Similarly, each of the two shorter sidewalls  218 - 220  each has a single such rib  222 . 
     Additionally, the shell  112  includes two further ribs  224  on each of the two shorter sidewalls, each extending upward from the bottom surface  212  of the shell  112 . These further ribs  224  are less intended for structural rigidity, and more intended to prevent stacks of rack shells made during the manufacturing, shipping, or handling processes from nesting so firmly together that they are difficult to separate. The further ribs  224 , as shown, protrude inwardly from the sidewalls  218 - 220  and are made from thicker material, thus not being present as depressions on the exterior surface  226 . 
     The ribs illustrated in  FIG.  2    and described herein represent one possible embodiment; in particular, it will be noted that the illustrated ribs  222 - 224  originate at the bottom surface  212  and extend upward along the sidewalls  214 - 220 . Other ribs, or additional ribs, in various configurations are possible and would meet the objectives of the present invention. Other such rib configurations, including protrusions and depressions originating near an open top end  230  of the shell or elsewhere on the sidewalls  214 - 220 , are deemed to be within the scope of the invention. 
     Each of the four sidewalls  214 - 220  flares outward near the open top end  230  of the shell  112 , forming a peripheral shoulder  232  around the interior surface  228 . This peripheral shoulder is configured to receive a tip deck ( FIG.  4   ). As shown in  FIG.  2   , the peripheral shoulder  232  is substantially continuous around the perimeter of the shell  112 , but it need not be so configured—it would be sufficient for the sidewalls  214 - 220  to flare inwardly at spaced locations, so long as the inwardly flared portions are strong enough to hold a pipette tip deck according to the invention. 
     In the illustrated embodiment, the four sidewalls  214 - 220  extend further upward from the peripheral shoulder  232 , forming a rounded upward-facing lip  234  and an outward-facing flange  236  around the lip  234 . The lip  234  and flange  236  are configured to receive mating surfaces of the lid  114 , as will be described in further detail below. 
     Also present in the rack shell  112  illustrated in  FIG.  2    are a plurality of apertures  238  defined by the longer sidewalls  214 - 216  at the peripheral shoulder  232 . Between each of the apertures and the top end  230  of the shell  112  is a retention protrusion  240  extending inward from the respective sidewall. The apertures  238  and protrusions  240  serve to retain a tip deck within the shell  112  as will be shown in further detail in connection with  FIG.  4   . 
     Referring now to  FIG.  3   , the lid  114  for a pipette tip rack  110  according to the invention is shown. The lid  114  has a generally flat top surface  312 —although in various embodiments the top surface  312  may have protrusions, depressions, or embossed or debossed areas as desired. Around a bottom portion  314  of the lid  114  is found a peripheral lip structure  316  and an outward-extending flange  318 . The lip structure  316  and flange  318  are configured to couple with and lie flush in a snug fit over the corresponding lip  234  and flange  236  of the body  112 , as shown in  FIG.  6   . The contact between the lip structure  316  and the lip  234 , and between the flange  318  and the flange  236  provide a secure frictional fit between the shell  112  and the lid  114 , preventing inadvertent dislocation of the lid, protecting the interior of the rack  110  against the intrusion of some dust and contaminants, while still allowing the lid  114  to be easily and readily removed from the shell  112  when desired. In an embodiment of the invention, there is at least one small protrusion found on an inner or outer surface of one or more sides of the lid, which would serve to prevent inordinately tight stacking of lid components during manufacturing, shipping, and handling. 
     As shown, the lid  114  further includes a stepped configuration with an intermediate surface  320  and intermediate wall  322 , but this configuration is primarily aesthetic, and as long as the lid  114  includes the lip structure  316  and flange  318 , as well as the top surface  312 , and the lid has a height sufficient to accommodate an array of pipette tips inside the pipette tip rack  110 , various contours and shapes for the periphery of the lid  114  can be imagined and would be within the scope of this invention. 
       FIG.  4    shows the shell  112  of a pipette tip rack  110  according to the invention with a tip deck  412  inserted. The tip deck  412 , which is preferably molded from a sufficiently rigid, lightweight, and recyclable polymer such as polypropylene (or other suitable materials), has a substantially flat upper surface  414  and defining an array of openings  416  to accommodate a plurality of pipette tips. As with traditional pipette tip racks, the array of openings  416  is arranged in an 8×12 matrix, each opening configured to receive a single pipette tip. Of course, other configurations are possible—the tips and openings need not be arranged in a rectangular array, and fewer or more than 96 tips (for example 384 or 1536 tips) may be loaded into a similar rack with an adapted tip deck. 
     The tip deck  412  is held in the body  112  of the pipette tip rack  110  in a flat, horizontal orientation against a top surface of the shoulder  232  defined by the sidewalls  214 - 220  of the body  112 ; for stability, the tip deck  412  should rest against the shoulder  232  ( FIG.  2   ) along at least two of the four opposing sidewalls  214 - 220 , but preferably the shoulder  232  extends around all four sidewalls  214 - 220 . As shown in  FIG.  2    and in  FIG.  4   , a plurality of inward-facing sidewall retention protrusions or “snap features”  240  above the shoulder  232  keep the tip deck  412  in place. When the tip deck  412  is inserted into the body  112  of the pipette tip rack  110  during the manufacturing or assembly process, the deck  412  can be snapped past the retention protrusions  240  to rest upon the shoulder  232 . The inward-facing retention protrusions  240  (and the rest of the body  112 ) are resilient enough to snap back into position and hold the deck  412  in place between the shoulder  232  and the protrusions  240 . 
     The apertures  238  ( FIG.  2   ) are provided to ensure the tip deck  412  snaps securely into place; each of the retention protrusions  240  has a sloped top surface  242  to enable pushing the tip deck into place past the protrusions. Once the tip deck  412  is past the protrusions, it snaps into place and is generally unable to be easily removed because the apertures  238  define a relatively sharp angle on lower edges  244  of the protrusions, and the protrusions extend over the edges of the tip deck  412  to create an interference fit. In an embodiment of the invention, accordingly, the tip deck  412  tends to cover part or all of the apertures  238 . If desired, the tip deck  412  can be provided with laterally extending features that enter the apertures  238  enabling an even stronger hold, but with the protrusions resiliently moving into position to cover the edges of the generally rectangular tip deck, such extending features may not be necessary. Moreover, it should be noted that the apertures are not necessarily required to hold a tip deck  412  according to the invention in place; protrusions may be simply formed in place in the sidewalls of the shell, with an interference fit formed as the tip deck is pushed past the uncut protrusions. If desired, even greater structural rigidity can be conferred upon the cellulose shell by using a modified tip deck with extensions that protrude out from the snap feature apertures  238  and grasp the shell exterior, thereby preventing bowing or other deformation of the shell during tip loading. 
     It may be observed in  FIG.  4    that the lip  234  of the shell  112  extends upward from the tip deck  412 . Preferably, the lip  234  is sized to allow partial tip loading on a multichannel pipette—i.e., a multichannel pipette may straddle the edge of the rack  110  to mount tips on only some of the channels of the pipette, and the lip  234  is preferably configured to be low enough in height to avoid interference with such a partial tip loading operation. In such a configuration (and as shown in  FIG.  5   ), the array of tips will generally sit on the tip deck  412  with their proximal mount ends extending from the top of the tip deck  412  to above the lip  234 , and accordingly, the lid  114  will need to have sufficient height to accommodate those proximal mount ends. 
       FIG.  5    illustrates a slightly different embodiment of a tip rack  510  according to the invention; this embodiment is taller than the rack  110  illustrated in  FIGS.  1 - 4    and would accommodate larger pipette tips, such as the illustrated tips  530 . The rack lid  512  and shell  518  are shown in cutaway form. 
     One difference evident in  FIG.  5    is that the lid  512  has a different shape from the lid  114  shown in  FIG.  3   ; it includes a single set of vertical walls  514  rather than the stepped configuration of  FIG.  3   . The lid  512  of  FIG.  5    further includes a depression  515  which serves to accommodate a bottom surface of another rack when the racks are stacked. These configurations and others will be understood by the reader to be within the scope of the current invention. 
       FIG.  5    further shows a tubular sleeve  516  inserted within the shell  518  of the pipette tip rack  510 ; as illustrated the sleeve is made from a folded and glued piece of paper that rests on an internal bottom surface  520  of the shell and is directly adjacent to the sidewalls  522 . The height of this tubular sleeve is specifically configured to allow it to make direct contact with the underside of the tip deck. Although the sleeve is described as “tubular,” it is more rigorously described as a truncated rectangular pyramid—with four flat sides  524 , each of which is trapezoidal in shape, formed into a configuration that defines a rectangular bottom opening  526  and a larger rectangular top opening  528 . 
     A suitable pattern  710  for the tubular sleeve  516  is shown in  FIG.  7   , in which it is apparent that four trapezoidal sides  524  are joined together with an additional flap  530  to facilitate gluing the paper sleeve  516  into its preferred truncated pyramidal shape. 
     Returning to  FIG.  5   , it is apparent that there is a relatively tight fit between the sleeve  516  and all four sidewalls  214 - 220  ( FIG.  2   ) of the shell  518 . Accordingly the pipette tips  532  held within the rack  510  according to the invention and resting on a tip deck  534  extend through the array of openings  416  ( FIG.  4   ) and hang downward, with their distal ends extending into the interior cavity of the shell  518  inside the sleeve  516 . 
     It is understood that when a pipette tip rack containing tips is handled, the tips may jostle around in the rack, and sometimes impact, rub against, or rest against one of the sidewalls of a rack. In a pipette tip rack  510  according to the invention, the tubular sleeve  516  is made from a material that is more resistant to abrasion and impacts than the cellulose pulp that forms the lid  512  and the shell  518 . Such a material may include various forms of refined paper (containing fewer or smaller fibers), plastic, Tyvek®, or other suitable materials. The sleeve  516  lines the interior of the shell  518  and limits loose fibers from the cellulose material from coming loose and potentially contaminating the pipette tips  530 : as the sleeve sits on the bottom surface  520  of the shell  518 , the four sides of the sleeve rest against or very near the sidewalls of the shell  518 . 
     Additionally, the sleeve  516  has an upper end  536  that sits directly below the tip deck  534 , thereby providing additional support and structure to the tip deck  534  and the pipette tip rack  510  as a user depresses a pipette into the rack  510  to mount the tips  530 . 
       FIG.  8    shows an overhead view of a sleeve  812  inserted into a rack shell  814  according to the invention. As can be seen, the sleeve rests snugly within the rack shell slightly below the apertures, protrusions, and shoulder intended to receive a tip deck, but in direct contact with the underside of the tip deck and each of the trapezoidal sides  524  ( FIG.  45   ) of the sleeve  516  rests on or near a corresponding sidewall  816  of the shell  814 . 
     Because the structure of a pipette tip rack according to the invention is primarily made from cellulose fiber, it can be advantageous to include additives in or coatings on the molded pulp to (1) improve the rack&#39;s performance in wet or moist conditions, and (2) lock or encapsulate cellulose fibers so they are less free to come loose from the rack  110  ( FIG.  1   ) and contaminate the pipette tips stored therein. 
     One such possible additive is an alkyl ketene dimer (AKD), which when added in small proportions to the cellulose fiber pulp, which is commonly used in paper and cardboard to improve moisture resistance. When used in small portions in a pipette tip rack according to the invention, it improves the moisture resistance of the body  112  and lid  114  while retaining adequate biodegradability. 
     Various coatings are also possible, including silicones, oils, polymerized oils, and aqueous coatings, that may not only be water resistant but would encapsulate fibers from the cellulose pulp. Such coatings may be applied to the interior, the exterior, or all surfaces of a pipette tip rack according to the invention. It is expected that an advantageously used coating may reduce to some extent, but certainly not eliminate, the biodegradability characteristics of a tip rack according to the invention. 
     For adequate strength, it is envisioned that a pipette tip rack according to the invention would include molded cellulose pulp parts—including the walls and surfaces of the rack shell and lid—that are advantageously between approximately 0.75 mm and 1.25 mm in thickness, though some portions of a rack according to the invention (including, for example, the internal ribs  224  of  FIG.  2   ) may be thinner or thicker. The foregoing range of thicknesses has been found to provide an advantageous relationship between weight (and accordingly, expense) and strength. 
     It should be observed that while the foregoing detailed description of various embodiments of the present invention is set forth in some detail, the invention is not limited to those details and a pipette tip rack with characteristics according to the invention can differ from the disclosed embodiments in numerous ways. Similar pipette tip racks using may be fabricated in comparable or different ways, including via folded flat fibrous stock, and may differ in various morphological characteristics. Although the invention is described and illustrated in the context of a rack for an array of 96 disposable air displacement pipette tips, it is equally applicable to other types of other pipette tips and articles, including positive displacement tips, sample tubes, and other like items, or arrays or rows of more or fewer items. It should be noted that functional distinctions are made above for purposes of explanation and clarity; structural distinctions in a system or method according to the invention may not be drawn along the same boundaries. Hence, the appropriate scope hereof is deemed to be in accordance with the claims as set forth below.