WO2009127015A2

WO2009127015A2 - Heat transfer fabric, system and method

Info

Publication number: WO2009127015A2
Application number: PCT/AU2009/000484
Authority: WO
Inventors: Paul Laursen; Kamal Alameh; Mikhail Vasiliev; Michael Newton
Original assignee: Edith Cowan University
Priority date: 2008-04-17
Filing date: 2009-04-17
Publication date: 2009-10-22
Also published as: WO2009127015A3

Abstract

A heat transfer fabric (10) or material, the fabric or material comprising a conduit (14) containing a fluid and a focussing means (12) arranged to focus heat onto the conduit such that the fluid absorbs heat from adjacent the fabric and flows to a heat sinking means (16) where the absorbed heat is dissipated.

Description

Heat Transfer Fabric, System and Method

The present invention relates to a fabric/material, a system and a method, and particularly, although not exclusively, to a fabric/material, system and method for transferring heat, energy or radiation away from or towards a body.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Furthermore, throughout the specification, unless the context requires otherwise, the word "include" or variations such as "includes" or "including", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Background Art

Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application, or patent cited in this text is not repeated in this text is merely for reasons of conciseness.

Reference to cited material or information contained in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in Australian or any other country.

Under resting thermoneutral climatic conditions (i.e., 18-22°C), approximately 90 Watts of metabolic heat energy is both produced and removed from a human body through heat transfer processes of convection, conduction, and radiation. Under these conditions, heat transfer is balanced, and a homeostatic life- sustaining core body temperature of about 37°C is maintained. Under these thermoneutral conditions, radiative heat loss in the infrared region of the electromagnetic spectrum approximates 90 W on a resting naked human body. At an ambient temperature of 30⁰C however, radiative heat loss is reduced to -45 W, which instead leads to heat gain and a resulting increase in core body temperature. To solve this problem, humans evolved the efficient heat removal mechanism of sweat evaporation, which liberates 2270 kJ of energy per litre of sweat evaporated, or 630 Watts of heat energy over a one hour period. This mechanism of heat removal with sweating works efficiently to control body temperature under conditions conducive to evaporation.

There are situations however where the process of heat loss with sweating becomes impaired. Examples include 1) conditions of high environmental humidity

(high vapour pressure), such as that experienced in the tropics, 2) when an insulate layer of clothing forms a barrier separating the skin from the surrounding environment (i.e., thick clothing), and 3) with aging, where sweat rate is lowered.

All of these examples can lead to a situation known as uncompensatable heat stress, which causes core body temperature to rise uncontrollably. An increase in core temperature of only 1°C above normal is perceived as uncomfortable, causes dehydration due to sweating, and lowers physical work capacity.

Sustained body temperatures of more than 5°C above normal are fatal. It is accordingly desirable to transfer heat away from the body of a person suffering from such a condition.

As well as arising in the medical treatment of patients suffering from conditions such as uncompensatable heat stress, the heat removal problem affects a number of important occupations throughout the world, including the military, mining industry and fire service, for example, all of which require a workforce to wear protective clothing not conducive to sweat evaporation. Indeed, the creation of a practical heat removal device for these workers has challenged scientists to date. As noted in the Australian Bureau of Transport and Regional Economic report (Bureau of Transport and Regional Economics Report 2004, Risk in Cost Benefit Analysis: Implications for Practitioner. Working Paper 61, Bureau of Transport and Regional Economics: Canberra p 35.) "a significant breakthrough in reducing heat strain while wearing (protective) clothing in field conditions is needed". It has been shown that utilisation of techniques to reduce the core temperature of the body can have a significant effect on the performance of athletes in hot conditions. Methods used in the past as an attempt to cool the body of athletes includes both pre-cooling prior to performing and cooling during the event. While pre-cooling, such as using cold plunge pools or ice jackets may provide some advantage over no cooling, the results achievable are limited in relation to cooling of the body during performance.

Athletes such as cyclists have used articles of clothing containing a pre-cooled fluid during the event. This provides some advantage over pre-cooling but such clothing is bulky and therefore adds additional weight to the athlete. Further, the cooling effect is limited in time as the cooled fluid will eventually rise in temperature as it absorbs heat from the athlete.

Problems also arise in situations where, conversely, body temperature drops below that required for normal metabolism and bodily functions. When the body is exposed to cold, its internal mechanisms may be unable to replenish the heat that is being lost to its surroundings, leading to potentially fatal conditions such as hypothermia. Accordingly, there are many situations in which, rather than cooling, a heating or heat retaining effect is required, for example in the medical treatment of a patient suffering from hypothermia, or during outdoor activities performed in cold climates.

Disclosure of the Invention

In accordance with a first aspect of the present invention there is provided a fabric or material for transferring heat, comprising a conduit containing a fluid and a focussing means arranged to focus heat onto the conduit such that the fluid absorbs heat from adjacent the fabric and flows to a heat sink where the absorbed heat is dissipated.

Preferably, the fabric further comprises reflecting means operable to reflect heat towards the focussing means.

Preferably, the fabric further comprises a plurality of conduits and/or a plurality of focussing means.

Preferably, the plurality of conduits and the plurality of focussing means are arranged in arrays in which the array of conduits is aligned with symmetry axes and focal plane locations of the focussing means.

Preferably, the source of the heat is radiation.

Preferably, the conduit and/or focussing means is woven within the fabric.

Preferably, the conduit and focusing means comprise an optical fibre, a waveguide, or a microfluidic channel.

Preferably, the focusing means comprises a cylindrical lens or a cylindrical microlens.

Preferably, the components of the fabric are provided on a substrate.

Preferably, the focussing means and/or the fabric substrate are coated or micro- /nano- structured for increased antireflection of heat radiation.

Preferably, the fabric further comprises cooling means for cooling the fluid.

Embodiments of the first aspect of the present invention relate to a fabric that will allow the transfer of heat away from the body while remaining relatively light weight. While the fabric will have applications such as in clothing for athletes, as mentioned above, it may be used in any situation in which transfer of heat is advantageous. For example, it may be used in clothing for use by members of the military, mine workers, fire fighters or any person wishing to control temperature around a body. It may also be used in clothing for animals or pets to control body temperature on hot days. It may be incorporated into other articles such as sheets for use in the medical treatment of patients requiring cooling.

A second aspect of the present invention relates to a heat transfer fabric in which heat is transferred towards the wearer.

In accordance with the second aspect of the present invention there is provided a fabric or material for transferring heat, the fabric having a first surface, the fabric comprising a conduit containing a fluid and a reflecting means, wherein the reflecting means is arranged such that heat released from the fluid within the conduit is reflected in a direction towards the first surface.

Preferably, the fabric further comprises a second surface opposed to the first surface, wherein the reflecting means is arranged between the conduit and the second surface of the fabric or on the second surface of the fabric.

Preferably, the fabric further comprises a plurality of conduits and/or a plurality of reflecting means.

Preferably, the source of the heat is radiation.

Preferably, the conduit and/or reflecting means is woven within the fabric.

Preferably, the conduit comprises an optical fibre, a waveguide, or a microfluidic channel.

Preferably, the reflecting means comprises a reflection coating.

Preferably, the fabric further comprises heating means for heating the fluid. Preferably, the components of the fabric are provided on a substrate.

In accordance with a third aspect of the present invention, there is provided a heat transfer system comprising a fabric or material according to the first or the second aspects of the present invention as hereinbefore described, a reservoir for storing the fluid in fluid communication with the conduit, and control means for controlling fluid flow from within the reservoir through the conduit.

Preferably, the control means comprises a pump to pump fluid from within the reservoir through the conduit.

Preferably, the heat transfer system further comprises sensing means for sensing a temperature adjacent to the fabric, and processing means operably coupled to the sensing means and the control means to control the fluid flow from within the reservoir through the conduit in response to the sensed temperature.

Preferably, the sensing means comprises a Bragg grating.

Preferably, the heat transfer system further comprises heating means for heating the fluid, and/or cooling means for cooling the fluid.

In accordance with a fourth aspect of the present invention, there is provided a heat transfer method comprising: focussing heat onto a fluid contained in a conduit such that the fluid absorbs heat and directing the fluid to a heat sinking means where the absorbed heat is dissipated.

Preferably, the method further comprises cooling the fluid.

Preferably, the method further comprises sensing a temperature, processing the sensed temperature and controlling the fluid flow in response to the sensed temperature.

In accordance with a fifth aspect of the present invention, there is provided a heat transfer method comprising reflecting heat released from a fluid in a conduit in a direction towards a first surface. Preferably, the method further comprises heating the fluid.

Preferably, the method further comprises sensing a temperature, processing the sensed temperature and controlling fluid flow in the conduit in response to the sensed temperature.

In accordance with a sixth aspect of the present invention, there is provided a method of fabricating a heat transfer fabric structure comprising forming focussing means by melting and subsequently re-solidifying solid-phase rectangular microstripes of adhesive material arranged on an optical substrate.

Preferably, the focussing means comprises cylindrical microlenses.

In accordance with a seventh aspect of the present invention, there is provided an article comprising a fabric or material according to the first or the second aspects of the present invention as hereinbefore described. The article may additionally comprise a heat transfer system according to the third aspect of the present invention as hereinbefore described.

Preferably, the article comprises: a textile, an item of clothing, or a sheet/blanket or a sleeping bag.

Brief Description of the Drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a cross section view of an optic fibre of a heat transfer fabric in accordance with an aspect of the present invention;

Figure 2 is a cross section view of a plurality of the optic fibres of Figure 1 stacked within the heat transfer fabric;

Figure 3 shows a heat transfer system incorporated within clothing having a heat transfer system in accordance with an aspect of the present invention; Figure 4 shows a temperature sensing system incorporated within clothing having a heat transfer system in accordance with an aspect of the present invention;

Figure 5 shows an alternative embodiment of heat transfer fabric in accordance with an aspect of the present invention;

Figure 6 shows an example design of a cross-section of a patch of another embodiment of a heat transfer fabric in accordance with an aspect of the present invention;

Figure 7 shows optical parameters of the heat transfer fabric of Figure 6 optimised using ZEMAX optical design software to achieve a high efficiency of heat capture through focussing and fluid absorption of IR radiation;

Figure 8 shows a microphotograph of the heat transfer fabric of Figure 6 made of NOA73 adhesive using reflow technology;

Figure 9 shows the developed heat-transfer fabric demonstrator of Figure 6;

Figure 10 shows results of preliminary demonstrator manufacture of the heat transfer fabric of Figure 6 made with optical fibre imprints using UV15 epoxy as a base material;

Figure 11 shows a close-up microscope image showing excellent surface quality and periodicity of the cylindrical lens array of the heat-transfer fabric of Figure 6;

Figure 12a shows an experimental setup demonstrating the uniformity of the microlens array of the heat-transfer fabric of Figure 6;

Figure 12b shows a regular spot array generated by illumination of the microlens array of the heat-transfer fabric of Figure 6 with a HeNe laser; and

Figure 13 shows a microphotograph of ink solutions propagating through the microstructured arrayed microfluidic waveguide of the heat-transfer fabric of Figure 6. Best Mode(s) for Carrying Out the Invention

Referring to the Figures, there is shown a heat transfer fabric 10 or material in accordance with the first aspect of the invention described above including a plurality of conduits for containing a fluid and a plurality of focussing means. In the embodiment shown in Figures 1 and 2, the conduit comprises a hollow core 14 running throughout the length of an optic fibre 12. The fibre 12 acts as the focussing means. The provision of one or more apertures running through the length of an optic fibre is known and said apertures can be created with existing technology.

The fibres 12 are woven within the fabric/material. The fibres 12 may be provided in a stacked formation, such as shown in Figure 2, such that when the fabric/material is worn, at least portions of the wearer's body is substantially surrounded by the fibres 12.

The core 14 within the fibre 12 is filled with a fluid arranged to flow along the length of the fibre 12. The fluid may be a gas or a liquid (such as water) and is selected to have suitable characteristics to allow absorption of heat from adjacent the fabric 10 and flow of the fluid to heat sinking means in the form of a heat sink 16 where the heat is dissipated.

The material or fabric 10 has a first surface 18 to be arranged in use adjacent to the body of a wearer and second opposed surface 20. That is, the first surface 18 is that surface from which heat is to be absorbed. The core 14 is positioned within the fibre 12 such that heat flowing from the direction of the first surface 18 of the fabric is focussed toward the core 14, where it is absorbed by the fluid within the core 14. Further, the fibre 12 is provided with reflecting means in the form of a high reflection 22 coating adjacent the second side 20 of the fabric 10. The high reflection coating 22 reflects heat not incident on the core 14 back toward the core 14 for absorption by the fluid. Heat beams may undergo multiple reflections within the fibre 12 before being absorbed by the fluid 14. This is advantageous as it results in more energy being absorbed by the fluid. Figure 3 shows an embodiment of a heat transfer system 23 in accordance with an aspect of the present invention. In the embodiment described, the heat transfer system 23 is used within clothing formed of the heat transfer material/fabric 10. The system 23 comprises reservoir means in the form of an input fluid reservoir 24 and an output fluid reservoir 26, a fluid transferring or pumping means in the form of a fluid pump 28, control means in the form of a one way valve 30 and the heat sink 16.

The input reservoir 24 contains the fluid to flow through the fibres 12 and is in fluid communication with the cores 14 of the fibres 12. The pump 28 is arranged to pump fluid from within the input reservoir 24 through the fibres 12. The output reservoir is in fluid communication with the cores 14 of the fibres 12 such that fluid flowing through the cores 14 exits the fibres 12 into the output reservoir 26. The output reservoir 26 is provided with the one way valve 30 connected to a fluid line 32. The fluid line 32 returns the fluid from the fibres 12 to the input reservoir 24 via the heat sink 16, where heat absorbed by the fluid when the fluid was in the fibres 12 is dissipated.

The pump 28 may be powered by any suitable source, including mechanical or electrical means. It is envisaged that, for example in the case of athletes, the pump 28 may be mechanical and powered by movement of the athlete. For example, by pedal power of a cyclist or by a pump mechanism in the shoe or a runner powered by the force of the shoe striking the ground.

In this embodiment of the invention, the material of the heat transfer fabric 10 is provided with one or more temperature sensors arranged to detect the temperature adjacent to a location in the fabric 10. A processing means in the form of a processor is provided with application software stored in memory coupled thereto and operable to receive this temperature information and control the flow of fluid within the fabric 10 accordingly to maintain the detected temperature at a desired level programmed into the heat transfer system 23. The heat transfer system 23 as shown in Figure 3 is provided with control means in the form of a plurality of electronically driven micro-valves 34 between the input reservoir 24 and the fibres 12. The micro-valves 34 are controlled by the processor such that fluid is allowed to flow through a selected set of fibres 12. In this way, fluid may be directed through fibres 12 passing over areas which require the most cooling.

Figure 4 shows a temperature sensing arrangement in which the fibres 12 woven within the fabric 10 are used to provide the temperature sensing. The system includes a plurality of sensing means in the form of Bragg gratings 36 provided along the length of one or more fibres 12. Also provided are pulsing means in the form of a pulsed laser 38, a coupler 40 and a detector and processor 42 with application software stored in memory coupled thereto to provide the functionality described below and operate a pump control output 44. A pulse is sent along the fibre 12 and is reflected by the Bragg gratings 36. The train of reflected pulses, corresponding to reflections from the Bragg gratings 36 have amplitudes related to the temperature at each of the Bragg gratings 36. The fibres 12 having the Bragg gratings 36 are positioned within the fabric 10 to be adjacent positions at which it is desired to sense the temperature. The detector and processor 42 controls the operation of the micro-valves 34 as mentioned above based on calculated temperatures along the length of the fibres 12 having the Bragg gratings 36.

Figure 5 shows an alternative embodiment of a heat transfer fabric 10 in accordance with an aspect of the present invention. The heat transfer fabric material 10 includes a sheet of suitable material 50 in which is provided the conduits. The sheet 50 may comprise a plastic material with the conduits being the in the form of a plurality of parallel waveguides 52. A first surface 18 of the sheet 50 is provided with focussing means in the form of a plurality of cylindrical lenses 54. Each cylindrical lens 54 is arranged on the first surface 18 of the sheet 50 over a corresponding waveguide 52 such that heat flow incident on the cylindrical lens 54 is focussed onto the waveguide 52 in the same manner as shown in the first embodiment of the present invention.

In accordance with the second aspect of the present invention as hereinbefore described, the heat transfer fabric 10 includes a plurality of conduits provided by the hollow cores 14 of the fibres 12 as shown in Figure 1. The fibres 12 are also provided with reflecting means in the form of the high reflection coatings 22 on the fibres 12 adjacent the second surface 20 of the fabric 12 as shown in Figure 1.

The fluid is again provided through the cores 14 in the fibres 12. However, it is provided with heat by use of heating means in the form of a heat source, rather than a heat sink 16, provided as part of the heat transfer system. Heat is thereby applied to the fluid which flows through the cores 14 of the fibres 12. Heat released from the fluid towards the second surface 20 of the fabric 10 is reflected by the high reflection coatings 22 back towards the first surface 18 and therefore towards the wearer.

It is envisaged that a single garment comprised of the fabric as describe above could perform both a heating and a cooling function by controlling of the flow of fluid and the direction of heat transfer to the fluid in the heat transfer system. For example, a change from a cooling function to heating could result from initially simply stopping the fluid flow within the fibres 12. With no fluid flow, heat cannot be transferred away by the fluid and will be reflected back towards the wearer by the high reflection coatings 22. Additional heating could then be provided by initiating the flow of fluid and using the same heat source to heat the fluid before entering the fibres 12.

In another embodiment of the invention, cooling means is also provided to cool the fluid.

In embodiments of the invention, the heating means and/or the cooling means may be controlled by the processor in response to the detected temperature to adjust the temperature of the fluid as required.

One- and two-dimensional interferometric lithography processes have successfully been used to fabricate microfluidic channels of cross-section areas as small as 10x10 μm². High-resolution imprint lithography has recently emerged as a very promising technology for the fabrication of Integrated Circuits (ICs) and nanofluidic devices. However, one of the challenges facing such processes is the precise etching of microfluidic channels using cost-effective high-volume fabrication. Recently, new techniques for the application-specific control of fluid flows in microfluidic channels have successfully been demonstrated.

The infrared (IR) radiation emitted by the human body at the mid-infrared wavelength during heavy exercise can be seen as a bright "light bulb", emitting tens of Watts of invisible light.

A cross-section of a patch of another embodiment of a heat transfer fabric material 101 in accordance with an aspect of the present invention is illustrated in Figure 6. Figure 6 is a principal design diagram of the photonic fabric structure. In this embodiment, the fabric 101 has a microstructured arrayed microfluidic waveguide structure for IR radiation focussing and transfer.

The waveguide structure is comprised of Masterbond UV-curable epoxy UV15 and consists of focussing means in the form of an array of a cylindrical microlens 103 that focuses IR radiation (such as that from the body of a wearer of clothing incorporating the fabric 101) onto conduit means in the form of arrayed microfluidic channels 105 forming a fluidic loop etched onto an epoxy layer 107 deposited on top of a supporting substrate 109. In the embodiment described, the substrate 109 measures 75mmx25mm. The IR radiation is the source of heat from the wearer's body.

In the embodiment described, the focussing means and the fabric substrate are coated or micro-/nano- structured for increased antireflection of heat radiation.

The removal of heat is assisted by concentrating the emitted IR radiation (from the body of the wearer) for absorption on a fluid comprising a liquid medium moving through the arrayed microfluidic channels 105. In the embodiment described, the fluid is water. In alternative embodiments, other fluids can be used. A feature of the fabric design of this embodiment is high degree of alignment of the precision- positioned arrayed fluidic microchannels 105 with the symmetry axes and the focal plane locations of the cylindrical microlenses 103. This is advantageous in increasing the efficiency of absorption of the incident energy within the moving fluid. Cooling means in the form of a thermoelectric cooler (TEC) in conjunction with a heat sink is used as the means for cooling the fluid circulating in the fluidic loop formed by the microchannels 105. The relationship between the cross-section of the microfluidic channels 105 and the cooling power required is optimised by maximising the IR radiation that is focused at different positions along the fluid flow.

The optical parameters of the fabric 101 can be optimised using ZEMAX optical design software to achieve a high efficiency of heat capture through the far- infrared light focussing and subsequent water absorption of the radiation. This is shown in Figure 7. In the embodiment described, the radius of curvature of the cylindrical microlenses 103 was 62.5 μm. This is advantageous as it enables the imprint mask for forming the fabric 101 to be realised using conventional optical fibres, leading to cost-effective and precise imprint mould. In alternative embodiments of the invention, the cylindrical microlenses 103 may have curvatures of other dimensions.

Whilst the components of the fabric 101 may be of any suitable dimensions, a distance between the microlenses 103 and the microfluidic waveguides 105 of 85 μm and a waveguide cross-sectional area of 50μm ^χ50μm provides enhanced performance.

The heat transfer fabric structure of the described embodiment was fabricated using fibre imprint moulding and epoxy re-flow technologies. The re-flow microfabrication process involved the formation of the cylindrical microlenses 103 by melting and later re-solidifying solid-phase rectangular microstripes of adhesive material (NOA73) arranged on an optical substrate. In alternative embodiments of the invention, other suitable materials may be used in the process, such as other polymer materials. The re-flow technology provided a high degree of alignment of the microlenses 103 and microfluidic channels 105. A high degree of optical alignment and suitable lens surface qualities are preferable for improved performance. The high degree of alignment achieved through the use of precision-positioned fluidic microchannels 105, symmetry axes and focal plane locations, increases the efficiency of absorption of the incident IR light energy within the moving fluid, thereby achieving an increased efficiency of heat capture through far-infrared light focussing and subsequent absorption of the radiation on the centralised fluid medium.

Figure 8 shows a microphotograph of the heat transfer fabric 101 made of NOA73 adhesive using reflow technology.

An experimental setup for demonstrating the heat transfer fabric 101 is shown in Figure 9. In this embodiment, a commercial Bartels Mikrotechnik mp5 USB- controllable microfluidic pump is used for fluid propagation. In alternative embodiments of the invention, other pumping means can be used, as described previously.

Figure 10 shows the optical quality inspection of the heat transfer fabric 101. The surfaces of the cylindrical microlens 103 were inspected under a microscope to reveal their surface features and to estimate the degree of microlens 103 array alignment. A diffraction pattern generated by the microlens 103 array under Helium-Neon (HeNe) laser illumination showed regular features, thus demonstrating the periodicity of the array and confirming the suitability of the adopted microphotonic technology to fabricate high-quality heat-focusing cylindrical lens arrays.

A close-up of the microscope field of view showing the excellent lens surface quality is shown in Figure 11 , where HeNe laser light was used to illuminate the heat transfer fabric 101. Figure 11 illustrates the alignment/parallelism, lateral spacing uniformity, surface quality and the accurate curvature of the fabricated microlens 103 array. Further investigations involving thermodynamic modelling, optimisation and characterisation of the device performance in terms of IR absorption efficiency and fluid throughput are ongoing by the owner.

Figure 11a shows an experimental setup for optical inspection of the fabricated heat transfer fabric 101. Illumination of the cylindrical microlens 103 array (acting as a diffraction grating) with a HeNe laser light resulted in a periodic diffraction pattern which confirmed the array periodicity with reduced irregularities. The ability of the heat transfer fabric 101 to propagate the flow of liquid within its microchannels 105 was also tested. Ink flows through the microfluidic channels 105 are shown in Figure 12, confirming the suitability of the reflow technology to fabricate microfluidic channels for the transfer of infrared light, heat transfer, and energy transfer.

In embodiments of the invention, components thereof such as the type and amount of fluid provided and the microfluidic channel shape and dimension range can be varied to enable desired performance such as optimum laminar flow with minimum viscosity loss.

In accordance with another embodiment of the invention, the microstructured arrayed waveguide structure of the heat transfer fabric 101 is incorporated into a textile fabric to enhance surface heat removal.

Embodiments of the present invention provide a breakthrough in heat transfer efficiency (towards or away from a body) through the combined technologies of microfluidics, microtechnology and optics.

Embodiments of the present invention therefore provide a photonic heat-transfer fabric or material to control human (and other organisms) body temperature using the integrated technologies of microfluidics and optics. The removal of body heat can be assisted by concentrating the emitted infrared radiation for absorption on a liquid medium moving through microfluidic channels engineered within a textile material. Thus, "reverse-action wetsuits" can be realised by combining modern photonics and optical technology. Embodiments of the present invention offer a solution for the heat transfer problem, and have application as a lightweight textile material that can be integrated into a garment or other articles (such as sheets or sleeping bags) to enhance body heat removal or addition for prolonged periods. Such garments and articles have the capacity to revolutionise survival clothing for the military, the fire service and the resource industry, and in medical patient treatment, amongst others. Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. It should be further appreciated by the person skilled in the art that variations and combinations of features described above, not being alternatives or substitutes, can be combined to form yet further embodiments falling within the intended scope of the invention.

Claims

The Claims Defining the Invention are as Follows:

1. A heat transfer fabric, the fabric comprising a conduit containing a fluid and a focussing means arranged to focus heat onto the conduit such that the fluid absorbs heat from adjacent the fabric and flows to a heat sinking means where the absorbed heat is dissipated.

2. The fabric according to claim 1 , further comprising reflecting means operable to reflect heat towards the focussing means.

3. The fabric according to claim 1 or 2, further comprising a plurality of conduits and/or a plurality of focussing means.

4. The fabric according to claim 3, wherein the plurality of conduits and the plurality of focussing means are arranged in arrays in which the array of conduits is aligned with symmetry axes and focal plane locations of the focussing means.

5. The fabric according to any one of the preceding claims, wherein the source of the heat is radiation.

6. The fabric according to any one of the preceding claims, wherein the conduit and/or focussing means is woven within the fabric.

7. The fabric according to any one of the preceding claims, wherein the conduit and focusing means comprise an optical fibre, a waveguide, or a microfluidic channel.

8. The fabric according to any one of the preceding claims, wherein the focusing means comprises a cylindrical lens or a cylindrical microlens.

9. The fabric according to any one of the preceding claims, wherein components of the fabric are provided on a substrate.

1O.The fabric according to any one of the preceding claims, wherein the focussing means and/or the fabric substrate are coated or micro-/nano- structured for increased antireflection of heat radiation.

11. The fabric according to any one of the preceding claims, further comprising cooling means for cooling the fluid.

12.A heat transfer fabric, the fabric having a first surface, the fabric comprising a conduit containing a fluid and a reflecting means, wherein the reflecting means is arranged such that heat released from the fluid within the conduit is reflected in a direction towards the first surface.

13.The fabric according to claim 12, further comprising a second surface opposed to the first surface, wherein the reflecting means is arranged between the conduit and the second surface of the fabric or on the second surface of the fabric.

14.The fabric according to claim 12 or 13, further comprising a plurality of conduits and/or a plurality of reflecting means.

15.The fabric according to any one of claims 12 to 14, wherein the source of the heat is radiation.

16.The fabric according to any one of claims 12 to 15, wherein the conduit and/or reflecting means is woven within the fabric.

17.The fabric according to any one of claims 12 to 16, wherein the conduit comprises an optical fibre, a waveguide, or a microfluidic channel.

18.The fabric according to any one of claims 12 to 17, wherein the reflecting means comprises a reflection coating.

19.The fabric according to any one of claims 12 to 18, wherein components of the fabric are provided on a substrate.

2O.The fabric according to any one of claims 12 to 18, further comprising heating means for heating the fluid.

21. A heat transfer system comprising a fabric according to any one of the preceding claims, a reservoir for storing the fluid in fluid communication with the conduit, and control means for controlling fluid flow from within the reservoir through the conduit.

22.The system according to claim 21 , wherein the control means comprises a pump to pump fluid from within the reservoir through the conduit.

23.The heat transfer system according to claim 21 or 22, further comprising sensing means for sensing a temperature adjacent to the fabric, and processing means operably coupled to the sensing means and the control means to control the fluid flow from within the reservoir through the conduit in response to the sensed temperature.

24.The heat transfer system according to claim 23, wherein the sensing means comprises a Bragg grating.

25.The heat transfer system according to any one of claims 21 to 24, further comprising heating means for heating the fluid, and/or cooling means for cooling the fluid.

26.A heat transfer method comprising: focussing heat onto a fluid contained in a conduit such that the fluid absorbs heat and directing the fluid to a heat sinking means where the absorbed heat is dissipated.

27.The method according to claim 26, further comprising cooling the fluid.

28.The method according to claim 26 or 27, further comprising sensing a temperature, processing the sensed temperature and controlling the fluid flow in response to the sensed temperature.

29.A heat transfer method comprising reflecting heat released from, a fluid in a conduit in a direction towards a first surface.

3O.The method according to claim 29, further comprising heating the fluid.

31. The method according to claim 29 or 30, further comprising sensing a temperature, processing the sensed temperature and controlling fluid flow in the conduit in response to the sensed temperature.

32.An article comprising a fabric according to any one of claims 1 to 20.

33.An article comprising a heat transfer system according to any one of claims 21 to 25.

34.A method of fabricating a heat transfer fabric structure comprising forming focussing means by melting and subsequently re-solidifying solid-phase rectangular microstripes of adhesive material arranged on an optical substrate.

35.The method according to claim 34, wherein the focussing means comprises cylindrical microlenses.

36.A heat transfer fabric substantially as hereinbefore described with reference to the accompanying drawings.

37.A heat transfer system substantially as hereinbefore described with reference to the accompanying drawings.

38.A heat transfer method substantially as hereinbefore described with reference to the accompanying drawings.