WO2019229475A1

WO2019229475A1 - Swab holder and its manufacture

Info

Publication number: WO2019229475A1
Application number: PCT/GB2019/051517
Authority: WO
Inventors: Christopher RAISON
Original assignee: Smiths Detection-Watford Limited
Priority date: 2018-06-01
Filing date: 2019-05-31
Publication date: 2019-12-05
Also published as: GB2574262A; GB201809013D0

Abstract

A swab holder for a sample collection probe, the holder comprising a swab for collecting a sample from a surface to be tested, the swab comprising a foraminous material and, a body of molded material for attaching the holder to said sample collection probe wherein the material of the body is integrated with the foraminous material thereby to secure the swab to the holder.

Description

SWAB HOLDER AND ITS MANUFACTURE

Field of Invention

The present disclosure relates to apparatus for the collection of samples for trace analyte detection to detect substances of interest in the samples, it also relates to the manufacture of such apparatus.

Background

In facilities such as airports and venues where large numbers of people may gather, there is a need to detect traces of substances of interest such as explosives, chemical weapons, and illegal drugs. Analysis to detect these substances may be referred to as trace analyte detection and may be performed using spectrometers.

A variety of different techniques can be used for trace analyte detection. These methods include ion mobility spectrometry (IMS), mass spectrometry, gas chromatography, liquid chromatography, and high performance liquid chromatography (HPLC) .

A variety of different methods can be used to introduce a sample into a detection instrument and the method will depend, in part, on the type of sample being analysed and the detection technique.

One sampling method involves contacting an object or other substrate to be tested with a fabric sampling swab which collects analyte particles. Upon contact of a sampling swab with a substrate to be tested, solid sample particles can become imbedded into the porous structure of the swab.

If the sample is in liquid form, the liquid can absorb into the fibres of the swab. The swab can then be placed into a detection instrument and the sample thermally desorbed from the swab for analysis . Summary

Aspects and examples of the present disclosure are set out in the claims .

Brief Description of Drawings

Embodiments of the disclosure will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 shows an elevation view of a swab holder for a sample collection probe;

Figure 2 shows a series of steps in a method of molding a swab holder such as that illustrated in Figure 1;

Figure 3 illustrates two fabrics which may be used for swabs such as those described herein; and

Figure 4 is an illustration of a trace analyte detector.

In the drawings like reference numerals are used to indicate like elements .

Specific Description

To detect substances of interest carried on an article, the article can be swabbed to collect a sample, thermal desorption of parts of the sample from the swab facilitates the detection of substances of interest in the sample.

The material used for the swab may be resistant to thermal degradation at very high temperatures but may be mechanically fragile and liable to break if it is not correctly handled.

Embodiments of the present disclosure provide a swab holder for securely holding such a swab. The holder may comprise a swab for collecting a sample from a surface to be tested, the swab comprising a foraminous material; and, a body of molded material for attaching the holder to said sample collection probe; wherein the material of the body is integrated with the foraminous material thereby to secure the swab to the holder. For example the molded material of the body may fill foramina of the swab. This may be achieved by overmolding the body of the holder onto the swab. During the process of overmolding, the fibres of the swab may become impregnated by the material from which the body of the swab holder is molded. When that material sets, the swab may thus be integrated with the swab.

Figure 1 shows an elevation view of a swab holder 1000 for a sample collection probe. The swab holder 1000 comprises a swab 1002, and a body 1004.

The swab 1002 protrudes from a distal end of the body 1004.

The body 1002 of the holder 1000 illustrated in Figure 1 comprises a tube of square cross section having a channel 1006 through it from its proximal to its distal end. A clip 1008 extends from the proximal end of the body.

The swab 1002 protrudes from the distal end of the body 1000, and each of the two ends 1020 of the swab are held in opposite side walls of the square tube which makes up this body 1004. A length of the swab extends between these two end portions of the material of the swab, which are held captured in the material of the body. Because its ends are secured in the ends of opposite sidewalls of the tube, the free length of the swab 1002 spans the open end of the channel 1006 at the distal end of the body.

The swab 1002 comprises a foraminous material, which may comprise a plurality of fibres. The fibres may be arranged in a crosshatch pattern, for example they may be woven. The fibres may comprise a meta-aramid such as Nomex (RTM) . The body 1004 may be overmolded onto the swab so that the moldable material which makes up the body has flowed, during the molding process, into the foramina of the swab 1002. As a result, the swab material is integrated with the material of the body 1004. This secures the swab to the body. The moldable material may comprises a thermoplastic such as polyethylene (PET) or PEEK.

The clip 1008 may comprise an elongate resilient member having a recess 1010 on its underside for engaging with a corresponding protrusion on a sample collection probe inserted into the channel 1006 of the holder 1000.

In use, a swab holder 1000 such as that illustrated in Figure 1 may be secured to a sample collection probe by sliding the tip of the sample collection probe into the proximal end of the channel which passes through the body.

The clip 1000 which extends from the proximal end of the body can thereby engage with a corresponding clip on the body of the sample collection probe to secure the holder to the probe. When the probe is held in the channel it may protrude through the distal end of the channel to support the free length of the swab 1002 which extends from the holder. This can enable the sample collection probe to be applied to a surface to use the swab to collect substances of interest from the surface.

In the example illustrated in Figure 1, the tube part of the body of the holder has a rectangular lumen therethrough - in other words, the channel is rectangular, for example square, in cross- section. The walls of the tube are substantially flat. For example, the tube has a rectangular cross-section. It will be appreciated however, that other shaped tubes may also be used. For example, the cross-section of the tube may be square, round, for example circular. The swab illustrated in Figure 1 is held in the material of the body at both ends with the free length extending therebetween across the end of the channel. As a result, the swab illustrated in Figure 1 is held in an approximately U-shaped configuration in which both ends of the 'U' are held in the material of the body whilst the bend of the 'U' extends from the distal end of the body across the channel.

It will be appreciated in the context of the present disclosure however that the swab need not be held at both ends. For example, only a single end of the swab may be integrated with the material of the body as described above. In such embodiments the probe which extends through the channel may simply support the swab on one side.

The channel may enable the holder to be secured to a sample collection probe, for example by the probe being inserted into the channel. The free length of the swab may span an opening of the channel - for example the opening at the end of the channel. It may also span any other opening of the channel such as a side opening. In these and other embodiments, the channel may be arranged so that when in use a sample collection probe is secured in said channel a part of the sample collection probe is arranged to support the free length of the swab.

It will also be appreciated in the context of the present disclosure that the swab may itself be tubular or sock-shaped and held in the material of the body at one end so that the channel opens into a lumen inside the swab.

Figure 2 provides a schematic view of a molding tool for manufacturing a swab holder such as that illustrated in Figure 1. The molding tool comprises a cavity arranged to be filled with a moldable material. The cavity is shaped to form a body such as that described above with reference to Figure 1. In particular, this cavity is shaped as the negative of the body of the swab holder, for example it may be arranged to form a tube of square cross-section .

At the end of this cavity which corresponds to the distal end of the holder two slots are provided. These two slots are each located at the same end of two opposite sidewalls of the tube. These slots are thus provided at the distal end of the mold cavity. A removable rounded (e.g. semi-circular) mandrel may span the space between these two slots outside the cavity.

The molding tool may further comprises an end cap, or any other kind of retainer for gripping the swab against the mandrel and/or ensuring that the slots are closed and sealed. In the example illustrated in Figure 2, the end cap has a cavity therein of complementary form to the mandrel. That is to say, the end cap comprises a semi-circular cavity arranged to cooperate with the mandrel to hold a swab between the mandrel and the end cap so that the two ends of the swab extend into the body of the molding tool through the slots. The mandrel and/or the end cap may comprise closing means, such as a seal, adapted to grip the swab adjacent to the slot to seal the volume. This can enable the volume to be filled with moldable material with the swab held in place and supported by the mandrel.

A method of manufacturing a swab holder using the molding tool of Figure 2 will now be described. Initially, with the mold open, and the end cap spaced from the mandrel, a swab can be introduced into the slots at the distal end of the volume so that it extends from one side of the volume through a first one of the slots, over the semi-circular mandrel, back into the volume through the other of the two slots and thereby into the other side of the volume. The end cap can then be secured in place over the swab to hold the swab against the mandrel.

Where this cap abuts the molding volume, adjacent the slots, it may be secured against the swab/mandrel to close the volume. A moldable material can then be provided into the volume in a liquid state so that the moldable material flows into foramina (pores or holes) in the material of the swab which extends into the volume. The end cap can then be removed, the mold opened, and the newly molded swab holder removed to enable a further swab holder to be molded.

Figure 3 illustrates two examples of a foraminous material which can be used to provide the swabs described herein. Figure 3A shows a first example of such a material in which threads of foraminous material are woven together in a crosshatch pattern. The pattern comprises foramina (e.g. gaps) each of which is bounded by two adjacent weft threads and two adjacent warp threads of the pattern. As illustrated in Figure 3B, these threads may each comprise a plurality of fibres aligned together to provide the warp/weft thread. The spaces (the foramina) between adjacent threads may be larger than any space between adjacent fibers of those threads.

The foraminous material of the swabs described herein may comprise a synthetic fibre such as polyamide, for example an aramid, for example a meta-aramid such as Nomex® and/or Kevlar®.

Swabs of the present disclosure may thus comprise Kevlar® or Nomex® or a combination of Kevlar® and Nomex®. Kevlar and Nomex are trademarks of the E. I. DuPont Co. The fibers of such materials can be homogeneous or heterogeneous. By homogeneous it is meant that a fibre is of uniform composition. By heterogeneous it is meant that a fibre contains both more than one component which can optionally be arranged as longitudinal layers within an individual fibre. For example, a fibre can comprise both Nomex and Kevlar within a single fibre or a fabric can comprise homogeneous fibers of both Nomex and Kevlar. In one embodiment the Nomex material is any of Nomex® R E88C, (specified as 320B) , Nomex® MC 59207 (specified as 326A), Nomex® R E88C spunlaced fabric ( specified as 320A) , Nomex® MC 59032, Nomex® R E88C spunlaced fabric, or a combination of these materials. In another embodiment, the Nomex material is any of Nomex® R E88C, (specified as 320B) , Nomex® MC 59207 (specified as 326A) , Nomex® R E88C spunlaced fabric ( specified as 320A) , or a combination of these materials.

A swab for use in IMS should have absorption and desorption properties suitable for the analytes and substrates to be sampled, should be compatible with the geometry and processes performed by the instrument, should be durable and stable over a range of temperatures, including temperatures in excess of 400° C., and should be substantially free from contaminants and impurities capable in interfering with sample analysis.

Figure 4 shows an apparatus 1 in which the sample collector described with reference to Figure 1 may be used. The apparatus comprises a spectrometer 3, an inlet 7, and an air mover 6 for drawing a flow of air through the inlet 7. A sample collection probe having a swab carrier disposed on its tip may be inserted into the inlet 7 to provide a sample to the spectrometer 3.

The inlet 7 comprises a passage through which a flow of air to be sampled by the spectrometer 3 can flow. In Figure 4, the spectrometer 3 comprises an ion mobility spectrometer which is coupled to the inlet 7 by a sampling port 9, and comprises a reaction region 11 in which a sample can be ionised. The sampling port 9 can be operated to obtain a sample from the inlet into the spectrometer. Some examples of sampling ports include 'pinhole' ports and membranes.

A gate electrode 13 may separate the reaction region 11 from a drift chamber 15. The drift chamber 15 comprises a detector 17 toward the opposite end of the drift chamber 15 from the gate electrode 13. The drift chamber 15 also comprises a drift gas inlet 19, and a drift gas outlet 21 arranged to provide a flow of drift gas along the drift chamber 15 from the detector 17 towards the gate 13.

The sampling port 9 can be operated to sample air from the inlet 7 into the reaction region 11 of the spectrometer 3. The reaction region 11 comprises an ioniser 23 for ionising a sample. In the example shown in Figure 1 the ioniser 23 comprises a corona discharge ioniser comprising electrodes.

The drift chamber 15 also comprises drift electrodes 25, 27, for applying an electric field along the drift chamber 15 to accelerate ions towards the detector 17 against the flow of the drift gas.

In operation, in response to the spectrometer 3 being activated by an operator, the controller 2 operates the air mover 6 so that a flow of air is drawn through the inlet 7. A desorber may then be operated to heat the swab to provide vapour into the flow of air through the inlet.

Whilst the air mover 6 continues to draw the flow of air through the inlet the controller 2 controls the spectrometer sampling port 9 to obtain a sample from the heated flow of air in the inlet 7. The controller 2 then controls the spectrometer 3 to perform ion mobility spectrometry on the heated sample in the reaction region 11.

Although an ion mobility spectrometer has been described as one example of a trace analyte detection system it will be appreciated that embodiments of the present disclosure may be used in other trace analyte detectors.

It will also be appreciated in the context of the present disclosure that overmolding is a process where a single part is created using two or more different materials in combination. Typically the first material, sometimes referred to as the substrate, is partially or fully covered by subsequent material (overmold material) during the manufacturing process. In embodiments of the present disclosure, the substrate may comprise the foraminous material of a swab and the overmolded material may flow into holes or pores in the foraminous material thereby entrapping it in the body.

As used herein, "swab" and "sampling swab" are used interchangeably. "Swab" and "sampling swab" refers to a woven or non-woven fabric of any suitable material. The stability of swab fibre at high temperatures is particularly important in detection methods which involve heating the swab.

For example, in ion mobility spectrometry, a sampling swab is heated to desorb and vaporize sample particles collected by contact of the swab with a tested material. Thus a swab should be resistant to decomposition or degradation at high temperatures.

Swabs of the present disclosure may comprise a material which is not degraded up to a temperature of at least 300° C., for example at least 325° C., for example at least 350° C., for example at least 400° C., for example at least 450° C., for example at least 500° C. For example, such a swab may not be degraded when heated to a temperature of approximately 300° C. for up to approximately 2 minutes, for example up to 5 minutes.

The body of the swabs described herein has been described as comprising a tube, but it will be appreciated in the context of the present disclosure that the presence of a channel through the body is optional. It may have the advantage of allowing the probe to pass through the holder for supporting and/or heating the swab, but such a channel need not be present at all. And, if it is present, the swab need not necessarily span its open end.

Likewise, the square channel through the tube may enable the orientation of the swab to be fixed relative to the probe (e.g. so the holder does not twist on the end of the probe. However, it need not be square. It may simply be keyed with some irregular geometric feature to inhibit rotation of the holder about the probe and/or to ensure that the holder can only be mounted in a particular orientation with respect to the probe.

The foraminous material of the swab may comprise any laminar material having a plurality of pores (e.g. holes) therein. These pores may be provided by gaps between fibres, or threads comprising a plurality of fibres. These may be arranged in a crosshatch pattern. The material need not woven. Both woven and non-woven materials may be used.

One method of manufacturing a swab holder has been described above, but other methods are contemplated. In most of these methods however at least one end of a foraminous swab material is disposed in a cavity of a molding tool. The foraminous swab is arranged so that it extends through a slot in the wall of the mold cavity. The slot can be sealed by a sealing gland (e.g. a compliant member which may surround the slot to inhibit leakage of the moldable material as it flows into the mold.

Once the foraminous material is securely held in place in this slot, the liquid moldable material (such as a thermoplastic in a liquid or amorphous state) can be flowed or shot into the mold. This may be done at a pressure selected based on the properties of the foraminous material to inhibit damage to the swab. It can nonetheless flow into the foramina of the swab material. It may wet the fibres of the swab so that they become impregnated with the moldable material in its flowing state. Thus, as the moldable material sets in the mold, the swab becomes integrated with it. This overmolding process may assist in securing the swab to the body because it can distribute the mechanical force necessary to hold the swab in place over a large area of the swab. This may reduce the tendency of the swab to break.

Any feature of any one of the examples disclosed herein may be combined with any selected features of any of the other examples described herein. For example, features of methods may be implemented in suitably configured hardware, and the configuration of the specific hardware described herein may be employed in methods implemented using other hardware.

It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and/or distributed throughout apparatus of the disclosure. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit.

In some examples the functionality of the controller described herein may be provided by a general purpose processor, which may be configured to perform a method according to any one of those described herein. In some examples the controller may comprise digital logic, such as field programmable gate arrays, FPGA, application specific integrated circuits, ASIC, a digital signal processor, DSP, or by any other appropriate hardware. In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non- transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein. The controller may comprise an analogue control circuit which provides at least a part of this control functionality. An embodiment provides an analogue control circuit configured to perform any one or more of the methods described herein.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A swab holder for a sample collection probe, the holder comprising :

a swab for collecting a sample from a surface to be tested, the swab comprising a foraminous material; and,

a body of molded material for attaching the holder to said sample collection probe;

wherein the material of the body is integrated with the foraminous material thereby to secure the swab to the holder.

2. The swab holder of claim 1 wherein the material of the body being integrated with the foraminous material comprises the material of the body filling foramina of the swab.

3. The swab holder of claim 2 wherein the foraminous material comprises fibres and being integrated with the foraminous material comprises the fibres being trapped in a matrix provided by the material of the body.

4. The swab holder of claim 3 wherein the fibres are arranged in a crosshatch pattern.

5. The swab holder of any preceding claim wherein the foraminous material is woven.

6. The swab holder of any preceding claim wherein the foraminous material comprises an aramid fibre material, for example a meta-aramid fibre such as Nomex®.

7. The swab holder of any preceding claim wherein the swab comprises a strip of the foraminous material which is integrated with the material of the body at at least one end of the strip and comprises a free length of foraminous material which extends outside the body.

8. The swab holder of claim 7 comprising a channel configured to enable the holder to be secured to a sample collection probe, wherein the free length of the swab spans an opening of the channel .

9. A method of manufacturing a swab holder for a sample collection probe, the method comprising:

disposing a swab for collecting a sample into a molding tool, and

overmolding the swab with a moldable material thereby integrating the material of the body with material of the swab wherein the body is configured for securing the holder to a sample collection probe.

10. The method of claim 9 wherein the swab comprises a foraminous material.

11. The method of claim 10 wherein overmolding comprises flowing the moldable material in a flowable state into foramina of the foraminous material.

12. The method of claim 10 or 11 wherein overmolding comprises impregnating the foraminous material with the moldable material in its flowable state.

13. The method of claim 10, 11, or 12 wherein the foraminous material comprises fibres arranged in a crosshatch pattern.

14. The method of claim 13 wherein the foraminous material is woven

15. The method of any of claims 9 to 14 wherein the swab comprises an aramid material, for example a meta-aramid such as Nomex®.

16. The method of any of claims 9 to 15 wherein the swab comprises a strip of material, and arranging the swab in the molding tool comprises securing at least one end of the strip into a volume of the molding tool to be filled with the moldable material, so that part of the strip extends out of the volume.

17. A molding tool for manufacturing a swab holder, the molding tool comprising:

a volume to be filled with a moldable material to form a body of the holder for attaching the holder to a sample collection probe;

a swab retainer for securing at least one end of a foraminous swab in the volume while a part of the strip extends out of the volume to enable the volume to be filled with the moldable material with a swab held in the retainer thereby to integrate the molded body with the foraminous material to secure the swab to the holder.

18. The molding tool of claim 17, wherein the retainer is configured to seal the volume and to support the swab during molding of the body.

19. The molding tool of claim 17 or 18 wherein the retainer is arranged to secure two ends of the swab with a free length therebetween outside the volume.

20. The molding tool of claim 19 wherein the tool is arranged so that the body comprises a channel and the free length of the swab spans an end of the channel.