GB2563974B

GB2563974B - Improved sealing mat

Info

Publication number: GB2563974B
Application number: GB1806010.3A
Authority: GB
Inventors: Francis Day Paul
Original assignee: 4Titude Ltd
Current assignee: 4Titude Ltd
Priority date: 2017-04-11
Filing date: 2018-04-11
Publication date: 2019-10-30
Anticipated expiration: 2038-04-11
Also published as: GB201913743D0; GB201806010D0; GB2579436A; GB2563974A; GB2579436B; GB201705870D0

Description

IMPROVED SEALING MAT

Field ofthe Invention

The present invention relates to methods and apparatus for sealing and unsealing a plurality of wells or tubes. It is particularly applicable, but in no way limited, to a sealing mat assembly incorporating a plurality of individual sealing caps detachably held in a carrier sheet, for sealing an array of tubes or wells, such as an 8 x 12 array or matrix of 96 tubes or wells.

Background to the Invention

Multiwell plates, such as a plate provided with 96 individual wells or tubes in its upper surface are widely used forthe storage of samples and reagents, and forthe preparation, treatment and analysis of samples in the chemical and biological sciences fields. Often it is necessary or desirable to cover or seal some or all ofthe wells/tubes in the plate. A variety of means have been used to achieve this, including caps, lids, mats, adhesive seals and heat seals.

Sealing mats for sealing an array of wells or tubes are known that consist of a carrier sheet and a plurality of sealing caps formed as an integral unit and permanently joined to one another. These sealing mats allow an operator to seal and to open a large number of wells/tubes in a single operation. However, they suffer from the disadvantages that cross-contamination may occur when the sealing mat is removed, and that all the tubes have to be opened in order to gain access to one well/tube in the array.

Sheets of adhesive or heat seal material are an effective way of sealing an array of tubes, but are not generally suitable for sealing Random Access plates. Random Access (RA) plates provide a useful feature for many laboratory applications' including providing great flexibility in PCR work, allowing handling of individual stand alone wells detachably mounted in a 96 well or other plate well matrix format. Each well is detachably held in a rigid frame suitable for use with automation. Once containing a sample or reagents, the wells need to be sealed using seals that allow random access to individual filled wells, so that the wells can be removed from the plate as and when required. Random access to the contents of one or more wells in an array of wells is an important requirement in PCR work. A sealing mat for closing a matrix of reaction tubes is described in WO0117682 (Micronic BV). This describes a sealing mat comprising a carrier sheet provided with a multiplicity of sealing elements for sealing test tubes. The sealing elements each incorporate a peripheral groove into which an opening in the carrier sheet is accommodated. This arrangement has some disadvantages. An important requirement is that these caps must be removable from the tubes both manually and roboticaiiy as and when required. This is achieved in the Micronic BV design by an undercut or internal shoulder formed inside the body of the cap, as shown in Figure 4. A hooked tool can be inserted under this shoulder from above and an individual cap or row of caps can then be prized or levered out of the tube(s). No robotic tool is available. However, if the top of the cap incorporates an optically ciear window, or the top of the cap is domed, then this method of cap removal is not avaiiabie. Caps with fiat tops that are optically clear are required for fluorescence detection (e.g, qPCR) among other techniques.

By way of further background information, carriers for containers that engage with the container caps are described in US2006/278541 (Mendoza) and GB1401892 (Owens-Illinois inc). A connection cap invention is described in JP6053979 (Kyosai), but there is no groove of any kind in the caps to retain a carrier sheet. EP 0128778 (HSC Research Development Corporation) describes a multiwell specimen dish with lids.

It is an object of the present invention to overcome or mitigate some or all of the disadvantages outlined above.

Summary of the invention

According to an aspect of the present invention there is provided a sealing mat assembly comprising a carrier sheet incorporating a plurality of apertures, and a plurality of sealing caps, each aperture in the carrier sheet being sized and shaped to accommodate a sealing cap for sealing a weli or tube wherein the seaiing caps and the carrier sheet are made from different materials, and wherein each sealing cap has a main body and incorporates two spaced apart substantially parallel annular rows each comprising a series of individual protrusions extending outwardly from the main body of the seaiing cap, the distance between the two opposing annular rows of protrusions being adapted to accommodate and temporarily retain the carrier sheet, such that the sealing caps are detachably fixed to the carrier sheet.

Each row has a plurality of individual protrusions, in each row the individual protrusions are spaced apart from each other around the periphery/circumference of the sealing cap.

This arrangement of two opposing annular rows of multiple angularly spaced apart protrusions on the sealing cap is a particularly effective means for holding sealing caps in a carrier sheet in an easily detachable manner, in addition, the spaces between the protrusions in the lowermost annular row of protrusions provide spaces into which fhe blades or blade protrusions of a decapping tool can be located (see more below).

Preferably the protrusions in the opposing annular rows are staggered such that there is substantially no overlap between the protrusions in the opposing rows. In this way the protrusions in contact with the upper and lower surfaces of the carrier sheet alternate around the periphery of the sealing caps. This also has the advantage that the blade protrusions on the decapping tool can be designed to correspond in extent and position to the protrusions in the uppermost row of protrusions on the sealing cap, allowing easy positioning of the decappirsg tool. The blade protrusions of the decapping tool then automatically correspond to the gaps between the protrusions in the lower row of protrusions on the sealing cap.

Preferably the opposing rows of outwardly extending protrusions are located towards/proximate the top of the sealing caps.

Preferably the surface of each protrusion facing into the space between the opposing rows of protrusions is substantially planar. This arrangement ensures maximum contact between the protrusions and the carrier sheet, particularly when in a preferred arrangement each planar face is substantially normal or substantially perpendicular to a longitudinal axis of the sealing cap, and thus aligned with the surface of the carrier sheet. in one preferred embodiment the protrusions of the two opposing rows protrude/ extend outwardly from the main body of the sealing cap by substantially the same distance as each other, in an alternative preferred embodiment the protrusions of the two opposing rows protrude/ extend outwardly from the main body of the sealing cap by substantially different distances.

It is therefore possible that the protrusions in the lowermost row of protrusions could if desired extend outwardly from the main body of the sealing cap by more than the protrusions in the uppermost row of protrusions. By adjusting the relative sizes and extent of the upper and iower protrusions it is possible to control how tightly the sealing caps are heid in the carrier sheet, and subsequently the pressure required to remove the carrier sheet once the sealing caps have been inserted into an array of tubes/weils. The optimum protrusion size will be determined by the designer-based on the chosen materials used to manufacture the sealing caps and the carrier sheet which in combination with the size of the protrusions will influence the pressure or force needed to remove the sheet, in this way by increasing or decreasing the size of the upper row of protrusions, and thus the surface area of each protrusion in contact with the upper surface of the carrier sheet it is possible to optimise and controi the force or releasing pressure required to remove the carrier sheet in order to separate the sealing caps from the carrier sheet. By increasing or decreasing the size of the iower row of protrusions, and thus the surface area of each protrusion in contact with the iower surface of the carrier sheet, it is also possible to allow for and accommodate the force that has to be exerted on the sealing caps when the sealing mat assembly is ejected from the moulding tooi, without the caps becoming accidentally separated from the carrier sheet

Preferably each sealing cap incorporates an outwardly extending lifting tab and preferabiy the lifting tab is located at substantially the top end of each sealing cap. it is preferred that the Sifting tabs are substantially aligned with each other in a complete sealing mat assembly. These Sifting tabs make it easier for an operative to remove a cap from a tube manuaiiy, without a speciai decapping tool (see below).

Preferabiy the uppermost row of protrusions is located at substantially the top of the outer edge surface of the sealing caps.

The tops of the sealing caps can take a number of forms, including domed and fiat, in one preferred embodiment the top of the sealing caps are substantially transparent to visible light, which is particularly desirable for qPGR applications.

In one preferred embodiment the sealing caps may be made from a polyolefin such as polypropylene and the carrier sheet may be made from a flexible high temperature fiuoroelastomer such as VITON (RTM). Alternatively the sealing caps could be made from a thermoplastic elastomer such as Santoprene (RTM) and the carrier sheet from a harder material such as a polyethylene terephthaiate (PET) polyester film such as Mylar (RTM).

Some of the key factors regarding the choice of these materials are hardness, flexibility and melting temperature, such that the two materials do not fuse together during the manufacturing process, and to provide a differential in material properties which lends itself to removing the carrier sheet whilst leaving the caps in place. Other factors including optica! transparency, inertness and water permeability may also influence the choice of sealing cap material. But fundamentally for the sealing mat assembly to work effectively it requires a difference in the mechanical properties and the melting temperatures of the two different materials.

By forming the sealing caps and the carrier sheet from different materials it is possible to form the sealing caps from a materia! with particularly good sealing properties and optica! transparency properties, and the carrier sheet from a material with favourable properties for removing the carrier sheet from an array of sealed wells/tubes.

The term ’different materials' means materials that do not fuse together during the injection moulding process, although the materials could both come from the same general class of plastics materials, such as both being polyolefins or both thermoplastic elastomers.

Preferably the sealing caps are arranged in the carrier sheet in a matrix fashion, such as an 8 x 12 matrix pattern. A wide variety of matrix patterns are possible, such as 8, 16, 32, and 48 well matrix patterns by way of just a few of the matrix patterns that are possible.

Preferably the carrier sheet incorporates one or more alignment means and in one preferred embodiment the alignment means take the form of one or more apertures spaced around the perimeter of the carrier sheet

Also described is a decapping tool for removing a sealing cap according to the present invention, said decapping tool comprising a substantially tubular body having a top end and a bottom end and further comprising a row of inwardly extending spaced apart blade protrusions set around the internal periphery at the bottom end of the tubular body, the shape and spacing of the protrusions corresponding substantially to the spaces between the protrusions in the lowermost row of protrusions on the sealing cap. The decapping tool may also include a means to turn it; such as a handle or other grip. Where the sealing cap is formed from a substantially hard, rigid plastics material it is equally possible that the blades on the decapping tool can engage under the uppermost row of protrusions instead of the lowermost row of protrusions.

Also described is a method of removing a said sealing cap from the first aspect of the invention from a tube, said method comprising the steps of- (i) providing a decapping tool of the afore-said further aspect of the present invention; (ii) placing the decapping tool over the sealing cap to be removed such that the blade protrusions on the decapping tool are aligned with the spaces between the protrusions on the sealing cap; (iii) pressing the decapping tool firmly downwards; (iv) rotating the decapping tool a partial turn such that the blade protrusions on the capping tool are located under the protrusions on the sealing cap; (v) Sifting the decapping tool away from the tube to lever, prise or lift the cap away from the well.

The lugs on the sealing caps, where present provide a useful stop to prevent the decapping tool being turned too far and the blade protrusions becoming re-aligned with the spaces between the protrusions on the sealing cap.

Brief Description ofthe Drawings

Preferred embodiments ofthe present invention will now be described by way of example only with reference to the accompanying Figures wherein:-

Figure 1A illustrates a plan view of a sealing mat assembly according to the present invention;

Figure 1B illustrates a cross-sectional side view along section line A-A ofthe sealing mat assembly of Figure 1A;

Figure 1C illustrates an enlarged view of the top of a single sealing cap as Detail C shown in Figure 1A;

Figure 1D illustrates an enlarged cross-sectional view through a sealing cap and carrier sheet as Detail B shown in Figure 1B;

Figure 1E illustrates a perspective view of the sealing mat assembly shown in Figure 1A;

Figures 2A to 2D illustrates top, side, side and perspective views of a sealing cap; Figure 3 illustrates a perspective view ofthe top of a sealing cap assembly showing locator holes, the bottom part ofthe sealing caps being hidden by the carrier sheet; Figure 4 illustrates an enlargement of a corner ofthe sealing mat assembly shown in Figure 3;

Figure 5 illustrates a view ofthe underside of a corner ofthe sealing mat assembly shown in Figure 4 illustrating the bottom part ofthe sealing caps that project below the carrier sheet.

Description ofthe Preferred Embodiments A first embodiment ofthe invention is illustrated in Figures 1A to 1E which show a sealing mat assembly 10 comprising a carrier sheet 11 and a plurality, in this case 96, of sealing caps 12. Figure 1A shows a complete sealing mat assembly from above and Figure 1E shows a perspective view ofthe sealing mat assembly. The sealing caps 12 are fixed to or held in the carrier sheet in a detachable or demountable fashion or manner by a series of outwardly extending protrusions set around the outer periphery of each sealing cap and which serve, when the sealing mat is in an assembled configuration as shown in Figures 1A and 1E, to grip the carrier sheet.

Figure 2 shows more clearly that these protrusions 13, 14 are arranged in two substantially parallel spaced apart annular rows of individual protrusions, the two rows being spaced apart or separated along a longitudinal axis D-D ofthe cap as shown in Figure 1D. The protrusions 13A to 13 E in the upper row, or set, of protrusions are positioned at an upper level, and protrusions 14A to 14E in the lower row, or set, are positioned at a lower level, with the cap in the orientation shown in Figure 1D with the top of the cap uppermost. In this example the top of the upper set of protrusions 13A to 13E is located substantially level with or at the top of the sealing cap, although this is not essential. The lower set of protrusions 14A to 14E is located lower down such that the distance between the two internally opposing faces of the two opposing annular rows of protrusions is adapted to accommodate and temporarily retain the carrier sheet, such that the sealing caps are detachably mounted or removably fixed to the carrier sheet.

It will be understood from the Figures that the individual protrusions 13A-E, 14A-E project radially outwards from the main body of the sealing cap 12 and are arranged in two longitudinally spaced apart rings I annular rows. The surface of each protrusion facing into the space between the two opposing rows, shown as surfaces 15 and 16 in Figure 1D, are substantially planar, and each planar face is substantially normal or substantially perpendicular to the longitudinal axis D-D of the sealing cap. This provides a series of substantially flat surfaces, arranged substantially parallel to the upper and lower surfaces of the carrier sheet to resist movement of the carrier sheet in either an upward or a downward direction. The terms 'upward' and 'downward' relate to directions of movement with respect to the longitudinal axis of the sealing cap D-D with the cap in an upright position, as shown in Figure 1D.

An important feature of the protrusions in the present example is that there is substantially no overlap between the protrusions in opposing rows. This is more clearly seen in Figure 2 where protrusion 13E can be seen to be located in line with the space between protrusions 14D and 14E and so on. The protrusions in this example could be considered as two rows of non-overlapping crenulations spaced around the periphery of the sealing cap, the rows being spaced apart both along the longitudinal axis of the sealing cap and angularly displaced with respect to protrusions in the opposing row. Any dimensions shown in the Figures are purely by way of example only and are not intended to limit the scope of the present invention in any way.

Each sealing cap is provided with a lifting tab 17 to facilitate removing a cap from a sealed tube or well. The lifting tab 17 in this example is in substantially the same plane as the upper row of protrusions and the underside of tab 17 acts as one of that row of protrusions to prevent upward movement of the carrier sheet Advantageously these tabs are preferably substantially aligned with each other during manufacture as shown in Figures 1A and 1E. And preferably the tabs 17 are orientated in a direction away from the direction in which the carrier sheet is peeled away from an array of sealed wells or tubes, for ease of peeling the sheet away.

The carrier sheet 11 may be detached from the sealing caps 12 once the sealing caps have been firmly pressed into an array of wells/tubes by applying an upward force on the carrier sheet 11 and folding it; preferably in a direction in which the lifting tabs 17 are aligned. Friction between the sides ofthe wells/tubes and the sides ofthe holes in which they sit in a mounting plate or holder (not shown) helps retain the wells/tubes in their original array format. A gripping tab (not shown) may be provided along one edge ofthe carrier sheet to serve as a point by which to grip the carrier sheet and facilitate its separation from an array of sealed tubes/Wells.

Importantly the sealing caps 12 and the carrier sheet 11 are made from different plastics materials. In the manufacturing process a carrier sheet made from a first plastics material is provided, in which an array of holes or openings have been punched or cut out in preparation for accommodating an array of sealing caps. The carrier sheet should be of a suitable thickness as determined by the materials specialist but is generally between 0.2mm to 1.0mm thick, with 0.8mm being one preferred thickness. This carrier sheet is then placed taut in an injection moulding mould, such that each opening is located at the position of a mould cavity for a sealing cap. The carrier sheet is then clamped tightly between two mould halves of the injection moulding mould with the perimeter of each hole or opening in the carrier sheet projecting somewhat into a cavity in the mould. A second plastics material is then injected into the mould to form the sealing caps which, once the cooled sealing mat assembly has been ejected from the mould, are held captive on the carrier sheet 11 by the two rows of protrusions 13, 14 one above and one below the plane ofthe carrier sheet respectively.

One or more alignment means, in this example in the form of apertures or holes 18A to 18F spaced around the perimeter ofthe carrier sheet are provided to assist with the accurate placement of the carrier sheet in the injection moulding mould. These apertures or holes could also be used to facilitate the correct alignment of a sealing cap assembly with an array of wells/tubes. They could be used for example by a robotic handling machine or fit onto or over corresponding pins in a carrier or could be used in conjunction with an optical alignment system.

It is important that the carrier sheet 11 and the sealing caps 12 are formed from different plastics materials in order that the sealing caps and the carrier sheet do not fuse together during the moulding process. An example of a suitable material for the sealing caps is a polyolefin such as polypropylene (PP), especially a substantially clear or transparent PP. This has the advantage that even when sealed with a cap, this still leaves the contents of the tube visible so that certain measurements can be taken, such as measurement of fluorescence during qPCR. It is particularly beneficial if the top of the cap 19 shown in Figure 1D is thin, thinner than the cap side walls, in order to increase transparency, and to facilitate puncturing the top 19 of the sealing cap 12 with a needle in order to gain access to the contents of the tube.

An example of a suitable material for the carrier sheet is a thermoplastic elastomer (TPE), for example a flexible high temperature fluoroelastomer such as VITON (RTM). Alternatively, the carrier sheet may be made from a harder material such as a polyethylene terephthalate (PET) polyester film such as Mylar (RTM).

It will be appreciated that the forces exerted on the sealing caps that would tend to cause the sealing caps to separate from the carrier sheet are a force from below, for example when the sealing mat assembly is ejected from the mould, or a force from above, for example when the sealing cap is being forced down into a well or tube. These forces occur separately and at different times and therefore the surfaces on the protrusions which tend to resist those forces do not need to be opposite to each other. Hence as shown in Figure 2A-D the two rows of protrusions are preferably angularly offset from each other whereby the respective protrusions above and below the carrier sheet 11 do not overlap. No parts of the protrusions 13A-E of the upper row above the carrier sheet 11 are aligned (in the direction lengthwise of the cap) with the protrusions 14A-E of the lower row below the carrier sheet 11

The protrusions on opposing rows may protrude/extend outwardly from the general outer surface of the sealing cap by substantially different distances. It is therefore possible that the protrusions in the lowermost row of protrusions could, if desired, extend outwardly from the general outer side edge surface of the sealing cap by more than the protrusions in the uppermost row of protrusions. By adjusting the relative sizes and extent of the upper and lower protrusions it is possible to control how tightly the sealing caps are held in the carrier sheet, and subsequently the pressure required to remove the carrier sheet once the sealing caps have been inserted into an array of tubes/Wells. Another important force to be accommodated is the force that has to be exerted on the sealing caps when the sealing mat assembly is ejected from the moulding tool, without the caps becoming accidentally separated from the carrier sheet.

This latter force, encountered when the sealing mat assembly is ejected from the moulding tool, is particularly important in the case of a PCR sealing cap formed from an optically clear, hard polymer like PP. In this application the cap will not give when released from the carrier sheet so it is necessary to make the carrier sheet pliable in order to release the caps. A suitable carrier sheet material in this type of application is a silicon or VITON (RTM) sheet that has similar rubber like properties that one would find in a TPE cap. With this combination of materials there is a greater tendency for the caps to separate from the carrier sheet on ejection of the sealing mat assembly from the mould. The arrangement of alternating protrusions, extending outward from the general outer surface of the sealing cap by substantially different distances, lends itself to and can accommodate use of a wide variety of different plastics material whilst ensuring ease of carrier sheet removal after wells have been capped, as well as sealing cap retention during ejection from the mould. In this application the lower row of protrusions 14A-E preferably protrudes/extends further away from the general outer surface of the sealing cap 12 than the upper row of protrusions 13A-E.

The arrangement of spaces between the protrusions in a particular row provides another important advantage not available in any of the known prior art sealing mat assemblies. This advantage relates to the ability and ease of manually or robotically decapping a capped tube/Well. A further aspect of the present invention is therefore a decapping tool for removing a sealing cap 12 of the first aspect of the present invention. The decapping tool (not shown) comprises a substantially tubular body having a top end and a bottom end, with a row of inwardly extending spaced apart blade protrusions set around the internal periphery at the bottom end ofthe tubular body. The shape and spacing ofthe protrusions in the decapping tool corresponds substantially to the spaces between the protrusions in one or both ofthe rows of protrusions on the sealing cap. A means to turn the decapping tool, such as a handle or other grip, is provided.

The tubular body of the decapping tool must be made from a thin material, preferably metal, because the space between adjacent tubes held in a conventional 8 X 12 96 well matrix is very small, less than 2mm. This results in a very small distance between the caps on adjacent capped wells. The distance that the blade protrusions extend inwardly on the inside perimeter surface ofthe tubular body must also be small, and approximates to the depth or extent ofthe protrusions on either the uppermost or the lowermost row of protrusions on the sealing cap. These blade protrusions may have chamfered edges or sides to facilitate their movement under the underside ofthe sealing cap protrusions, or between the top ofthe well and the underside ofthe sealing cap, depending on which row of protrusions is chosen to locate the decapping tool blades under.

In practice, the method of removing a sealing cap according to the present invention from a capped tube using a decapping tool as described above suitably comprises the steps of:- (i) Placing the decapping tool over the sealing cap to be removed such that the blade protrusions on the decapping tool are aligned with the spaces between the protrusions on the sealing cap. In some cases this could be done by aligning the blade protrusions with the spaces between the upper row of protrusions 13, or with the upper row of protrusions themselves; (ii) Pressing the decapping tool firmly downwards. This ensures that the blade protrusions are resting on the top ofthe lowermost protrusions or the top ofthe tube/Well; (iii) Rotating the decapping tool a partial turn such that the blade protrusions on the capping tool are located under the protrusions on the sealing cap. The lug on the sealing cap, where present, may provide a useful stop to prevent the decapping tool being turned too far and the blade protrusions becoming re-aligned with the spaces between the protrusions on the sealing cap; (iv) Lifting the decapping tool away from the tube, complete with the sealing cap, to lever, prise or lift the cap away from the well.

This operation could be done manually or robotically, as desired, and be performed on a single capped tube or a row of capped tubes if a tool with a row of decapping tools is provided, with a means to rotate the individual tools in the row of tools in unison is provided.

It will be understood that sealing cap assemblies according to the present invention can be used to seal a wide variety of sizes and shapes of wells and tubes, including storage tubes of various sizes, microtitration plates and PCR microplates. The present invention is applicable to both Random Access plates and to standard fixed well plates such as fixed 96 well PCR plates. If access is required to just one well in an array of fixed wells, the present invention makes this possible, without the need to remove the whole of an adhesive or heat seal sheet, or remove a complete strip of 8 caps, which is the current practice at the time this was written.

Claims

1. A sealing mat assembly comprising a carrier sheet incorporating a plurality of apertures, and a plurality of sealing caps, each aperture in the carrier sheet being sized and shaped to accommodate a sealing cap for sealing a well or tube wherein the sealing caps and the carrier sheet are made from different materials, and wherein each sealing cap has a main body and incorporates two spaced apart substantially parallel annular rows each comprising a series of individual protrusions extending outwardly from the main body of the sealing cap, the distance between the two opposing annular rows of protrusions being adapted to accommodate and temporarily retain the carrier sheet, such that the sealing caps are detachably fixed to the carrier sheet.

2. A sealing mat assembly according to Claim 1 wherein the protrusions in the opposing rows are staggered such that there is substantially no overlap between the protrusions in opposing rows.

3. A sealing mat assembly according to Claim 1 or Claim 2 wherein the opposing rows of outwardly extending protrusions are located towards the top of the sealing caps.

4. A sealing mat assembly according to any preceding claim wherein the surface of each protrusion facing into the space between the opposing rows of protrusions is substantially planar.

5. A sealing mat assembly according to any preceding claim wherein the protrusions on opposing rows extend outwardly from the main body of the sealing cap by substantially the same distance.

6. A sealing mat assembly according to any of Claims 1 to 4 inclusive wherein the protrusions on the opposing rows extend outwardly from the main body of the sealing cap by substantially different distances.

7. A sealing mat assembly according to Claim 6 wherein the protrusions in the lowermost row of protrusions extend outwardly from the main body of the sealing cap by more than the protrusions in the uppermost row of protrusions.

8. A sealing mat assembly according to any preceding claim wherein each sealing cap incorporates an outwardly extending lifting tab.

9. A sealing mat assembly according to Claim 8 wherein the iifting tab is located at substantially the top end of each sealing cap.

10. A sealing mat assembly according to Claim 8 or Claim 9 wherein the iifting tabs are substantially aligned with each other in a complete sealing mat assembly.

11. A sealing mat assembly according to any preceding claim wherein the uppermost row of protrusions are located at substantially the top of the outer edge surface of the sealing caps.

12. A sealing mat assembly according to any preceding claim wherein the top of the sealing caps are substantiaily transparent to visible light.

13. A sealing mat assembly according to any preceding claim wherein the sealing caps are made from a polyolefin such as polypropylene.

14. A sealing mat assembly according to any preceding claim wherein the carrier sheet is made from a thermoplastic polymer.

15. A sealing mat assembly according to any preceding claim wherein the sealing caps are arranged in the carrier sheet in a matrix pattern.

16. A sealing mat assembly according to Claim 15 wherein the sealing caps are arranged in the carrier sheet in an 8 x 12 matrix pattern.

17. A sealing mat assembly according to any preceding claim wherein the carrier sheet incorporates one or more alignment means.

18. A sealing mat assembly according to Claim 17 wherein the alignment means takes the form of one or more apertures around the perimeter of the carrier sheet

19. Use of a sealing mat assembly according to any of Claims 1 to 18 inclusive for sealing microtubes or wells.