GB2601137A - Improvements in or relating to microplates - Google Patents

Abstract

A microplate frame 10 for use in a laboratory process involving thermal cycling, the frame comprising a deck portion 12 with an array of apertures 18 wherein the frame 10 is made from a biological composite (biocomposite) material, the biocomposite material being formed by a thermoplastic polymer resin and natural fibres. The thermoplastic resin may be polypropylene. The natural fibres are ideally plant fibres such as bamboo. A microplate comprising the microplate frame and a plurality of thermoplastic polymer wells wherein each well extends through a respective aperture of the array of apertures in the deck portion, and the frame and plurality of wells are permanently joined to from a unitary plate. Ideally, both thermoplastic polymers are the same. The microplate is formed such that the wells are flush with the openings of the apertures in the deck portion which allows a sealing film to be affixed over the openings of the wells and apertures by laser sealing. The microplate frame may be formed by injection moulding.

Description

IMPROVEMENTS IN OR RELATING TO MICROPLATES

The invention relates to the frame portion of a two-component microplate that is used in a laboratory process that involves thermal cycling, and to a microplate including such a frame. The invention also relates to a method of manufacturing such a frame and plate.

It is known to use microplates for DNA analysis, such as genotyping or DNA amplification and such laboratory processes typically involve thermal cycling, that is to say a series of repeated heating and cooling profiles. Each temperature change may consist of multiple discrete temperature steps. Microplates are also known as microtiter plates, microwell plates or mulfiwell plates.

One such laboratory process is polymerase chain reaction (PCR) which is widely used to amplify deoxyribonucleic acid (DNA), thus permitting amplification of a very small sample of DNA to permit analysis of that DNA sample. A typical PCR process consists of a series of 20-40 repeated temperature changes often involving at least one denaturing step at a high temperature (e.g. approximately 95°C) followed by cycling of annealing (e.g. approximately 50-65°C) and elongation steps (e.g. approximately 68-75'C).

There are also derivative PCR processes. For example, the process of quantitative PCR (qPCR -also known as real time PCR (RT-PCR), which can be used to quantify DNA). The qPCR process also amplifies the DNA just as it does in standard PCR but it incorporates fluorescent tags into the process which provide readings throughout the amplification procedure that are used to quantify the amount of DNA. In this way, qPCR is often seen as an extension of the original PCR process.

Due to the thermal cycling profiles involved in such laboratory processes, the microplates must be able to withstand not only the elevated temperatures but also the repeated heating and cooling profiles without deforming (especially shrinking) or breaking.

Moreover, a lot of laboratory processes with thermal cycling are automated and typically use a robotic gripper to handle the microplate throughout the process. If a microplate used in such an automated process has distorted, warped or shrunk (e.g. due to its lack of rigidity and/or its lack of ability to withstand the thermal cycling profiles), then there is a risk that the robotic grippers will drop the plates after the laboratory process has taken place. This not only risks the samples in the wells of the plates being lost, but also means that laboratory personnel are required to monitor the automated process (which eliminates the possibility of the automated process running overnight without human intervention). For this reason, it is important that the microplates are dimensionally the same pre and post process (e.g. pre and post PCR process).

In addition, the PCR process can involve imparting a high pressure on the plate, (e.g. via a heated lid that is clamped over the plate during the thermal cycling process) which maximises the contact between the thin walled tube and the heating block and prevents sample condensation in the cap or seal. The heated lid applies such a force that the plate is driven into the heating block of the thermal cycler and can become stuck in the heating o block. To release the plates from the thermal cycler in an automated platform the robotic grippers must be able to grip tightly onto the skirt section of the microplate to separate it from the heating block. For at least these reasons, the microplates must also be suitably rigid to withstand robotic handling during the heat cycling process, According to a first aspect of the invention there is provided a microplate frame for use in a laboratory process involving thermal cycling, the frame comprising a deck portion having an array of apertures, wherein the frame is made from a biocomposite material, the biocomposite material including a thermoplastic polymer resin and natural fibres.

The frame comprising a deck portion with an array of apertures means that the plate can receive wells (which would contain a liquid sample, in use) to form a microplate. The frame may include a skirt portion that extends from the deck portion, which can help with handling and rigidity of the frame when being used in a thermal cycling laboratory process.

Forming the frame separately from the wells means that the two components can be formed from separate materials, each of which can be selected for suitability of the purpose of that component. For example, as explained above, the frame must be suitably rigid to withstand automated handling during the thermal cycling process. The PCR wells are typically made from virgin Polypropylene (PP) because PP is chemically inert, resistant to solvents, and ideally suited for injection moulding as PP allows for the production of precision thin-walled tubes, thus providing accurate thermal transfer and optimum PCR results. Moreover, microplates where the frame and wells are made from the same material (commonly PP) have a tendency to distort, shrink and bow after they have gone through the thermal cycling process.

Presently, the industry standard material for a microplate frame in a two-piece microplate (particularly for use in a PCR process) is polycarbonate or glass filled polycarbonate.

These materials have previously been thought of as the only commercially viable materials that can provide the thermal stability and rigidity required for PCR thermal cycling.

However, the inventor discovered that is was possible to make microplate frames from biocomposite materials which have the precision required in a microplate frame in terms of dimensions (e.g. position and size of the apertures so that they receive the wells and meeting the dimensional tolerances of the industry standard SBS footprint), while also having the rigidity and thermal stability required for thermal cycling without distortion at high temperatures. The inventor also found a mixture of materials that are commercially viable in terms of cost and production of the frame.

The standard SBS footprint referred to above is the standard established by the former Society for Biomedical Sciences (SBS) now the Society for Laboratory Automation and Screening (SLAS), which defines the dimensional requirements of the footprint of a microplate as specified in the American National Standards covering these microplates.

This standard helps with robotic compatibility so that laboratory automation could be designed to work with SBS compliant labware.

Forming the frame from a biocomposite material means that the frame is more environmentally friendly than the traditional polymer-only frames. It is becoming increasing important for companies to show that they are being "green", particularly larger companies who typically use high volumes of single-use or low-use plastic. Microplates are a high-volume and low-cost product, meaning that any improvement on the green credentials of the plate components will help with the overall sustainability.

Preferably, the natural fibres are plant-based fibres. More preferably the natural fibres are or include bamboo.

Bamboo has a natural rigidity and its fibre length is longer than other natural fibres, thus giving the material a high strength. Also, bamboo is fast growing, more sustainable and available all year round making it accessible for manufacturing high volumes of product.

The biocomposite material may be made up of more than 20% of natural fibres, preferably about 40% of natural fibres, preferably still about 50% of natural fibres, preferably still about 60% of natural fibres, optionally between 20% and 60% of natural fibres.

The percentage of natural fibres is important to obtain the optimum properties needed in a thermal cycling microplate. However, because of the dimensional precision required from such a plate and the volume of plates needed to be commercially viable, the bamboo percentage used should be compatible with the injection moulding process to achieve commercial viability. Forming the biocomposite material from as high a percentage as possible of natural fibres (and yet still being injection mouldable) also has the added benefit of increasing the "green" credentials of the material. The biocomposite material is able to have a higher percentage of non-resin material compared to typical glass filled polycarbonate because the natural fibres (particularly plant-based fibres) are not as abrasive. For example, typically, a maximum of 20%-25% of glass can be used in a composite material before the abrasive nature of the material wears down the manufacturing tools.

Preferably, the thermoplastic polymer resin has a melt temperature that is compatible with that of the natural fibres to allow forming of the frame by injection moulding without causing burning of the natural fibres.

Matching the melt temperature properties of the polymer resin in this way avoids damaging the natural fibres in the manufacturing process, which might degrade the mechanical properties, shape and/or aesthetic of the frame. Moreover, burning of the natural fibres may cause the material to develop an unpleasant odour, which is undesirable.

As an example, bamboo biocomposite has a melting temperature less than 180 °C. Therefore, a resin material should be chosen which has a melt temperature in this range or lower than this so that the biocomposite material can be formed into the frame without causing burning of the natural fibres. Polycarbonate, for example, would not be compatible because it has a melt temperature (for injection moulding) greater than 180°C and typically over 200°C, which is higher than that of bamboo.

In one embodiment, the resin is made from a polypropylene.

Polypropylene is a commercially viable and low-cost polymer which has the suitable characteristics to work as a resin in the biocomposite material. Moreover, the melt temperature of polypropylene is compatible with that of natural fibres, such as bamboo.

The frame may be formed by injection moulding.

Injection moulding is a commercially available and relatively low-cost method of manufacture. Being able to form the frame by injection moulding means that the frame can be produced in a commercially viable manner, particularly in relation to the high precision, high-volume, low-cost nature of the product.

Many existing products made from a biocomposite material (typically these are in a completely different field to laboratory equipment, such as coffee cups and kitchenware) are formed by processes other than injection moulding (for example compression moulding) and are often finished by hand; which would not be a commercially viable solution for the to high precision, high-volume, low-cost nature of this product. Moreover, compression moulding is not viewed as a process which produces products with precise dimensions, something that is required in the microplate frames to ensure robotic compatibility and that the wells fit snuggly into the apertures and the frames. The inventors were surprised to discover that the biocomposite material could be formed accurately into the frame with the desired dimensions.

Optionally, the deck portion typically has a thickness of up to and including 3 mm, preferably between 2.05 mm and 0.85 mm.

The walls of each aperture through the deck portion may be straight.

Such straight walls are more straightforward to manufacture than walls which include a ridge or indent. Typically, the aperture walls of a microplate frame will include at least one ridge/indent to help with engagement of the wells to the frame. However, this is not required in the frame of some embodiments of the invention because the outer surface of the wells fuse with the frame to permanently fix the wells to the frame (as described in more detail below).

The laboratory process involving thermal cycling is preferably PCR (as described herein), or a process derived from PCR such as qPCR.

According to a second aspect of the invention there is provided a microplate for use in a laboratory process involving thermal cycling, the plate including: a microplate frame as described hereinabove; and a plurality of thermoplastic polymer wells, each well extending through a respective aperture of the array of apertures in the deck portion of the frame, wherein the frame and plurality of wells are permanently joined to form a unitary plate.

The microplate enjoys the same benefits as outlined above in relation to the microplate frame.

The frame and plurality of wells may be permanently joined to one another by any suitable means.

Preferably, the thermoplastic polymer material of the wells matches the thermoplastic polymer resin of the biocomposite frame so that the outer surface of the polymer of the wells and the frame fuse together to form a unitary plate.

Such an arrangement means that the wells and frame are permanently joined to one another without the need for an additional locking mechanism or additional material or processing step (such as joining them together with a separate adhesive). In this way, the two components are effectively moulded together to form a unitary plate.

As indicated previously, this joining of the wells and frame means that the aperture walls in the deck portion can be straight (with no ridges/indents) because no additional attachment mechanism is required to join the two components together.

Optionally, the opening of the wells is flush with the opening of the apertures in the deck portion of the frame.

The flush wells and aperture openings provide a smooth finish on the upper surface of the deck portion. This permits the use of laser sealing, as explained in more detail below.

Such an arrangement is possible because the frame and wells are fused together (due to their matching thermoplastic polymer properties), and so an additional rim at the openings of the wells to lock over the openings of the apertures is not required.

In some embodiment, the microplate further includes a sealing film affixed over the flush openings of the wells and apertures by laser sealing, the sealing film being affixed in use after the samples have been added to the wells.

As indicated above, the flush arrangement of the wells and aperture openings lends itself to laser sealing. This is because both the rim of the well and the rim of the biocomposite frame aperture can both bond to the laser sealing film.

Currently, heat sealing is the main method of sealing samples within the wells of a two-piece microplate. This is because the heat seal is able to minimise sample evaporation by providing a strong bond between the rim of the polymer well and the heat seal film, which can withstand both cycling temperatures and the temperature of the heated lid (often between 105-110 degrees). For this to work, however, the rim of the well must be located over the rim of the frame aperture so that the polymer well provides a point of contact between the plate and the heat sealing material. Heat sealing on a flat (flush) surface will not create an effective bond due to the dimensional tolerance across the deck with small dips and raised sections that are not visible to the eye. Therefore, heat sealing a large flat surface results in patches that do not heat seal properly. It is also possible to use adhesive sheets and caps as a sealing means, but neither are as effective at sealing as heat sealing or laser sealing.

A laser sealer seals the sealing film to the top surface of the frame by using a laser beam that moves across and up and down the deck in straight lines in a grid formation. By sticking to straight lines in a grid, the laser only has to work on two axis and can seal the plate quickly (e.g.13 lines in columns and 9 lines in rows.) Currently, most conventional PCR plates have raised rims around the top of the wells. These raised rims provide both the locking mechanism needed to hold the wells into the frame plus they provide a specific point of contact for heat sealing or adhesive sealing to seal the reagents and samples in to the well. For a laser machine to seal a sealing film to such conventional PCR plates, the laser would have to individually go around each raised rim in turn. In a typical example of a conventional PCR plate, there would be 96 raised rims that the laser would have to navigate around. This would be very slow and time consuming and not practical for a laboratory plate processing point of view. It would also require a much more expensive laser system as it would have to accurately identify where the raised rim is on the deck to seal it.

For this reason, the conventional plates with raised rims do not lend themselves to laser sealing. Whereas, the flush rims outlined above in an embodiment of the invention, lends itself to laser sealing the reagents and samples into the well by laser welding in rows and columns in straight lines.

With the rapid development of lasers over recent years the laser sealer would be a cheaper instrument than an automated heat sealer, plus the laser sealer is more accurate which is more important with higher density plates such as 384 and 1536 well plates.

Laser sealing is an established sealing method for PCR plates but to date it is only compatible with one piece (single component) PCR plates that do not have a raised rim. As already outlined above, there are many drawbacks of the single component PCR plates, for example their tendency to shrink. The invention allows the use of laser sealing on two component plates for the first time as it does not require a raised rim to lock the tubes in to the deck and because the wells and deck fuse, thus preventing sample loss between the gap that is present between the wells and deck in a traditional two component plate that has a locking mechanism to form a unitary plate.

Commonly, microplates, such of those described here, have 96 or 384 wells (with the frame having the corresponding number of apertures).

According to a third aspect of the invention, there is provided a microplate frame for use in a laboratory process involving thermal cycling, the method comprising: using a biocomposite material, formed from a thermoplastic polymer resin and natural fibres, to form a frame having a deck portion with an array of apertures.

Injection moulding may be used to form the frame.

The advantages associated with the microplate frame of the first aspect of the invention apply mutatis mutandis to the method of the third aspect of the invention.

According to a fourth aspect of the invention there is provided a method of manufacturing a microplate for use in a laboratory process involving thermal cycling, the method comprising: the method of manufacturing a microplate frame as herein described above; providing a plurality of thermoplastic polymer wells; and forming a unitary plate by permanently joining the wells to the frame so that each well extends through a respective aperture in the deck portion of the frame.

Optionally, the step of joining the wells to the frame further includes forming a flush opening of each well with the respective aperture, the method further including: sealing the flush openings of the wells and apertures with a sealing film by laser sealing.

The advantages associated with the microplate of the second aspect of the invention apply mutatis mutandis to the method of the fourth aspect of the invention.

Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which: Figure la shows an upper side of a microplate frame according to a first embodiment of the invention; Figure lb shows a lower side of the microplate frame of Figure la; Figure 2 shows a cross-sectional view of a portion of the microplate frame of Figures la and lb; Figure 3 shows a cross-sectional view of a portion of a microplate frame according

to the prior art;

Figure 4a shows an upper side of a microplate according to a second embodiment; Figure 4b shows a lower side of the microplate of Figure 2a; Figure 5a shows an upper side of a microplate according to a third embodiment; and Figure 5b shows a cross-sectional view of a portion of the microplate of Figure 5a.

A microplate frame 10 according to the first embodiment of the invention is shown in Figures la, lb and 2. Starting with Figures la and lb, the frame 10 includes a deck portion 12 which is essentially flat in nature, and a skirt portion 14. The skirt portion 14 extends from the deck portion 12 in a single direction and around the full perimeter of the deck portion 12. In other embodiments, the skirt portion 14 may extend only partially around the perimeter or there may not be a skirt portion.

The frame 10 shown is rectangular in shape, but it may take any other form (square, circular, triangular, etc.).

The frame 10 is considered a thin wall construction. In the embodiment shown, the thickness 16 of the deck portion 12 is approximately 2 mm and the skirt portion 14 is approximately 0.9 mm. In other embodiments, the thickness 16 may be any suitable thickness, for example up to and including 3 mm, preferably between 2.05 mm and 0.85 mm.

The dimensions of the frame 10 in this embodiment are governed by the SBS footprint (as define above), which are: L = 127.76 mm and W= 85.48 mm. ± 0.25 mm. However, the frame 10 may have any suitable width W and length L. The deck portion 12 includes an array of apertures 18 formed therein. In this embodiment, there are ninety-six apertures 18 in total, arranged in an array of eight apertures along the width W of the deck portion 12 and twelve apertures along the length L of the deck portion 12. The apertures 18 are circular and have a diameter of approximately 7 mm. The apertures 18 are equally spaced (on a 9.0 mm pitch, which is the industry standard for plates with ninety-six wells) from one another and are arranged in a grid array with the centres of the apertures 18 in a given row or column being in line with one another.

The size, number and positioning of the apertures 18 may differ in other embodiments depending on the type of laboratory process the frame 10 is intended to be used, for 15 example.

The walls 20 of the apertures 18 (i.e. the inner walls 20 formed in the deck portion 12 from the apertures 18) are straight. In other words, they are uninterrupted or continuous in that they do not include any sort of ridge or indent portion. A straight walled aperture 18 is shown more clearly in Figure 2. In this embodiment the walls 20 of the apertures 18 are straight and run in parallel. In other embodiments the walls 20 may be straight (uninterrupted) but angled relative to one another to facilitate the injection moulding process.

Figure 3 shows the walls 20' of an aperture 18' of a deck portion 12' of the prior art. As can be seen, the walls 20' include a ridged portion 13 which acts as a locking mechanism between the aperture 18' and a well (not shown in this figure). As explained previously, this is not required in the deck portion 12 of the invention.

The frame 12 is made from a biocomposite material that is made up of a thermoplastic polymer resin and natural fibres (preferably plant fibres). In the embodiment shown, the resin is polypropylene (such that the material may be referred to as a "polypropylene biocomposite material"). Moreover, in this embodiment the natural fibres are bamboo. The biocomposite material in this embodiment includes 40% bamboo.

In other embodiments, the resin may be any other suitable thermoplastic polymer. However, the resin must be able to withstand the temperature cycling of the laboratory process and the high temperatures that are expected to be used in that process. In the case of PCR, as outlined previously, this may be upwards of 95°C, and so a polymer such as polystyrene would not work for PCR (although may be suitable for other processes). Moreover, the resin material should have a melt temperature that is compatible with that of the natural fibres to allow the biocomposite material to be formed into the frame 12 without causing burning and degradation of the natural fibres. In the case of the natural fibres being bamboo, polymers such as polypropylene and HDPE are compatible, whereas polycarbonate, Nylon and Polyether ether ketone (PEEK) are not.

Moreover, in other embodiments the natural or plant fibre may be any other suitable material. For example, it may be coffee husks or rice husks.

The biocomposite material may also include additional materials which make up a low percentage of the overall material composition. For example, it may include 1% of wax to help the bamboo (or other natural fibre) to be coated.

A microplate 50 according to the second embodiment of the invention is shown in Figures 4a and 4b. The plate 50 includes a microplate frame 10 as described above and shown in Figures la, lb and 2.

The plate 50 further includes a plurality of thermoplastic polymer wells 52. Each well 52 extends through a respective aperture 18 in the deck portion 12 of the frame 10. The wells 52 extend in the same direction as the skirt portion 14. The wells 52 taper from a wider opening 54 (at the aperture 18) to a narrower closed end 56. The wells 52 may take any

suitable form.

The frame 10 and the wells 52 are permanently joined to one another so as to form a unitary plate 50.

In this embodiment, the wells 52 are made from polypropylene which matches the polypropylene used as the resin in the biocomposite material of the frame 10. This means that the outer surface of the wells 52 and the polypropylene in the frame 10 fuse together (e.g. by heating) so as to permanently join the opening 54 of the wells 52 to the deck portion 12 of the frame 10.

As indicated previously, this joining of the wells 52 and frame 10 means that the aperture walls 20 in the deck portion 12 can be straight (with no ridges/indents) because no additional attachment mechanism is required to join the two components together.

Where the polymer resin of the biocomposite material of the frame 10 differs from polypropylene, the wells 52 can be made from the same polymer as the resin so as to achieve fusion between the frame 10 and the wells 52.

If the plate 50 is intended to be used for qPCR (as described previously), then the wells 52 could be coloured white by an addition of a white masterbatch to the tubing process that forms the wells 52. The resulting white wells 52 enhances the fluorescent signal that is generated from the amplified DNA and makes it easier to detect the signal.

A microplate 100 according to a third embodiment of the invention is shown in Figures 5a and 5b. the plate 100 is similar to the plate 50 of the second embodiment of the invention and like features share the same reference numerals.

The microplate 100 of the third embodiment of the invention differs from that of the second embodiment of the invention in that the deck portion 12 includes an array of three hundred and eighty-four apertures 18, and thus three hundred and eighty-four corresponding wells 52.

The width W and length L dimensions of the plate 100 are the same as defined above in relation to the plate 50 of the second embodiment (i.e. to conform to the SBS standard footprint). However, the aperture diameter is smaller (approx. 3.8 mm) and the pitch between the apertures is 4.5 mm.

In this embodiment, the opening 54 of the wells 52 is flush with the aperture 18 opening in the deck portion 12 of the frame 10. In this way, the upper surface of the frame 10 (with the well openings 54) is essentially flat/smooth. This differs from the wells 52 having a rim which protrudes on the upper surface of the deck portion 12.

The flush opening arrangement is possible because the frame 10 and wells 52 are fused together (due to their matching thermoplastic polymer properties), and so an additional rim at the openings 54 of the wells 52 to attach over the openings of the apertures 18 is not required.

The plate 100 may further include a sealing film (not shown) which is affixed over the flush openings 54 of the wells 52 and apertures 18 by laser sealing. Such a sealing film would be affixed after samples have been placed inside the wells 52. The sealing film would keep the samples inside the wells 52 during the laboratory process. As discussed previously, such laser sealing is possible because of the flat upper deck portion 12.

Testing The inventors carried out shrinkage testing on four different microplates to determine the percentage of overall shrinkage of the plates after a PCR process has been performed.

Such shrinkage results can be considered as representative of the overall stress trapped in the moulding of the plate (particularly the frame) which is released when the plate is subjected to heat cycling during PCR. As shrinkage can be directly correlated to warp or distortion, it can be interpreted as the lower the shrinkage percentage, the less likely the frame is to show warp or distortion post-PCR.

The following samples where used in the testing: 1. A single piece polypropylene plate (brand name: 4titudee). This was, and to a certain degree still is, considered the industry standard. It was the original PCR microplate product that works well, other than it is not rigid enough for reliable automation and as more PCR setups are automated, especially the high throughput systems, its use has declined over recent years.

2. A two-piece plate with a polycarbonate frame and polypropylene wells (brand name: 4fitudee). The principle behind this design was to maintain the same PCR functionality as the single piece plates but create a stiffer frame. This improved the reliability of robot grippers handling the plate in a PCR system (especially post-PCR where the single piece plate will bow and distort) and also improved the positional accuracy for more reliable liquid handling and/or post-PCR analysis.

3. A two-piece plate with glass filled polycarbonate frame and polypropylene wells. This took the polycarbonate frame product to an even further stage of development. The addition of the 10-15% glass adds even more rigidity to the frame. As previously explained, the PCR process is a temperature cycling process and this along with the pressure of the heated lid that clamps down on top of the plate during the cycling process, can cause the plate to stick in the heating block of the thermal cycler. This more rigid frame can be gripped more tightly by the robot arm to help remove it from the thermal cycler block, thus improving the overall reliability and speed of the automated PCR system.

4. A two-piece plate with a polypropylene bamboo biocomposite frame (with 40% bamboo) and polypropylene wells. This is a sample of the frame according to the invention.

Each plate had the dimensions and aperture arrangement as described above in relation to the second embodiment of the invention (i.e. as shown and described in the Figures 4a and 4b). Each plate was subjected to the same PCR process. The PCR protocol and experimental process was as follows: 94°C for 5 min (1 cycle) 94°C for 30 sec 55°C for 30 sec (3 temp 25 Cycles) 72°C for 30 sec 72°C for 10 min followed by 4°C until the plate is removed from the cycler.

Width and length measurements were taken from set points on both sides of the PCR plate frame prior to being placed in the thermal cycler. Post-PCR, the plates were measured at the same set points. Four plates of each type were tested.

The percentage size change (shrinkage) was deduced by calculating the pre-PCR size, minus the post-PCR size, divided by the pre-PCR size, multiplied by 100.

The average percentage shrinkage results were as follows: Plate 1: 0.26% Plate 2: 0.06% Plate 3: 0.08% Plate 4: 0.09%.

Firstly, the difference in performance between the single piece plate (plate 1) and the two-piece plates (plates 2, 3 and 4) can be seen. The two-piece plates experience significantly less shrinkage compared to that of the single piece plate. This, coupled with the fact that the single piece plate is not as suitable for robotic automation (due to reduced rigidity), makes is clear that the two-piece plates provide for better PCR performance.

Secondly, it can be seen that the shrinkage percentages for the bamboo biocomposite plate (plate 4) and the polymer plates (plates 2 and 3) are very similar. Therefore, the biocomposite plate matches the performance characteristics of the traditional polymer plates, but with the added environmental benefits discussed previously.

Claims (16)

1. CLAIMS: 1. A microplate frame for use in a laboratory process involving thermal cycling, the frame comprising a deck portion having an array of apertures, wherein the frame is made from a biocomposite material, the biocomposite material being formed by a thermoplastic polymer resin and natural fibres.
2. 2. A microplate frame according to Claim 1 wherein the biocomposite material is made up of more than 20% of natural fibres, preferably about 40% of natural fibres, preferably still about 50% of natural fibres, preferably still about 60% of natural fibres, optionally between 20% and 60% of natural fibres.
3. 3. A microplate frame according to Claim 1 or Claim 2 wherein the natural fibres are plant-based fibres, preferably bamboo.
4. 4. A microplate frame according to any preceding claim wherein the thermoplastic polymer resin has a melt temperature that is compatible with that of the natural fibres to allow forming of the frame by injection moulding without causing burning of the natural fibres.
5. 5. A microplate frame according to any preceding claim wherein the resin is or includes polypropylene.
6. 6. A microplate frame according to any preceding claim wherein the frame is formed by injection moulding.
7. 7. A microplate frame according to any preceding claim wherein the deck portion has a thickness of up to and including 3 mm, preferably between 2.05 mm and 0.85 mm.
8. 8. A microplate frame according to any preceding claim wherein the walls of each aperture through the deck portion are straight.
9. 9. A microplate for use in a laboratory process involving thermal cycling, the plate including: a microplate frame according to any preceding claim; and a plurality of thermoplastic polymer wells, each well extending through a respective aperture of the array of apertures in the deck portion of the frame, wherein the frame and plurality of wells are permanently joined to form a unitary plate.
10. 10. A microplate according to Claim 9 wherein the thermoplastic polymer material of the wells matches the thermoplastic polymer resin of the biocomposite frame so that the outer surface of the polymer of the wells and the frame fuse together to form a unitary plate.
11. 11. A microplate according to Claim 9 or Claim 10 wherein the opening of the wells is flush with the opening of the apertures in the deck portion of the frame.
12. 12. A microplate according to any one of Claims 9 to 11 wherein the microplate further includes a sealing film affixed over the flush openings of the wells and apertures by laser sealing.
13. 13. A method of manufacturing a microplate frame for use in a laboratory process involving thermal cycling, the method comprising: using a biocomposite material, formed from a thermoplastic polymer resin and natural fibres, to form a frame having a deck portion with an array of apertures.
14. 14. A method according to Claim 13 including the use of injection moulding to form the frame. 25
15. 15. A method of manufacturing a microplate for use in a laboratory process involving thermal cycling, the method comprising: the method of manufacturing a microplate frame according to Claims 13 or 14; providing a plurality of thermoplastic polymer wells; and forming a unitary plate by permanently joining the wells to the frame so that each well extends through a respective aperture in the deck portion of the frame.
16. 16. A method according to Claim 15 wherein the step of joining the wells to the frame further includes forming a flush opening of each well with the respective aperture, the method further including: sealing the flush openings of the wells and apertures with a sealing film by laser sealing.