A device for heating a sample

Abstract

A device for heating a sample comprising: an enclosure comprising a plurality of electrically conductive walls; a first applicator configured to receive a first oscillating current at a first frequency; a second applicator configured to receive a second oscillating current at the first frequency wherein the second oscillating current is out of phase with the first oscillating current, and wherein, the device is configured to generate an oscillating electric field between the first and second applicators at a first wavelength, wherein one or both of the first applicator and the second applicator is configured to be grounded via the electrically conductive walls of the enclosure such that the passage of current through the walls of the enclosure generates a further oscillating electric field and wherein the enclosure is configured to receive the sample at a sample stage arranged between the first and second applicators.

Description

[0001] A DEVICE FOR HEATING A SAMPLE

[0002] Field

[0003] The present disclosure relates to a device for heating a sample.

[0004] Background

[0005] The demand for efficient thawing and heating of organic material has significantly increased across various sectors. In medical settings, the need to quickly and uniformly thaw cryopreserved tissues and organs for transplantation is critical. This process is vital to ensure that cells and tissues remain viable; prolonged thawing times can reduce cell viability. Similarly, there is a pressing need for the rapid and homogeneous thawing of blood serum, blood plasma, and the warming of red blood cells before transfusion to enhance patient care.

[0006] It is possible to cryogenically preserve human and animal tissues for decades via vitrification. During vitrification, the cooling process is so fast that ice crystals cannot form and capture cell membranes. However, thawing organs quickly enough to avoid damage has proven nearly impossible. If the tissue defrosts too slowly, ice crystals can form during the defrosting process as the tissue approaches the freezing point. If the tissue does not defrost uniformly, stresses caused by uneven expansion or contraction can damage the tissue.

[0007] In the food industry, especially in large kitchens, the need for efficient thawing and cooking methods is paramount. Traditional methods such as microwave heating, conventional heat radiation and heat convection, though widely used, present several limitations. These methods typically offer minimal penetration depth, leading to uneven heating while the internal parts of the load are heated slowly through surface heat transfer. This results in extended thawing and cooking times and often leads to unevenly heated food products.

[0008] Existing techniques for heating dielectric materials include the use of oscillating high- frequency electric fields generated between electrodes or multiple electrodes. However, such methods lack flexibility for varying load geometries and compositions, and the equipment tends to e bulky, making it unsuitable for smaller-scale applications such as in laboratories, emergency departments and kitchens. Furthermore, these techniques often fail to provide the rapid thawing necessary to avoid ice crystal formation. This may, in a medical setting, cause tissue damage to frozen organs. Summary

[0009] According to a first aspect of the present disclosure, there is disclosed a device for heating a sample comprising: an enclosure comprising a plurality of electrically conductive walls; a first applicator configured to receive a first oscillating current at a first frequency; a second applicator configured to receive a second oscillating current at the first frequency wherein the second oscillating current is out of phase with the first oscillating current, and wherein, due to the phase difference between the first and second oscillating currents, the device is configured to generate an oscillating electric field between the first applicator and the second applicator at a first wavelength corresponding to the first frequency, wherein one or both of the first applicator and the second applicator is configured to be grounded via the electrically conductive walls of the enclosure such that the passage of current through the walls of the enclosure generates a further oscillating electric field and wherein the enclosure is configured to receive the sample at a sample stage arranged between the first applicator and the second applicator within the enclosure.

[0010] In one or more embodiments, a longest electron path that electrons may travel in a single cycle of the oscillating current between two points on the walls of the enclosure may be equal to N multiplied by the first wavelength ±20% wherein N is an integer.

[0011] In one or more embodiments, the first applicator may be coupled to a current generator which is configured to generate the first oscillating current.

[0012] In one or more embodiments, the device may comprise an impedance matching apparatus configured to provide for impedance matching between the current generator, the first applicator, the enclosure and the second applicator.

[0013] In one or more embodiments, the first applicator may be coupled to the current generator via a first conductor arrangement and the impedance matching apparatus, wherein the first conductor arrangement extends through a first wall of the enclosure at a first aperture and wherein the first conductor arrangement is electrically insulated from the wall through which it extends.

[0014] In one or more embodiments, the impedance matching apparatus may comprise a conductive sheet arranged to surround components of the impedance matching apparatus, wherein the conductive sheet is in electrical contact with the enclosure and grounded in the first current generator, the first impedance matching apparatus may comprise at least one capacitor which is coupled between the conductive sheet and the first conductor apparatus and least one of an inductor and a capacitor which is coupled in series with the first conductor arrangement.

[0015] In one or more embodiments, the second applicator may be electrically coupled to a wall of the enclosure.

[0016] In one or more embodiments, the second applicator may be electrically coupled to a second wall of the enclosure via a second conductor arrangement comprising a first electrical conductor and a second electrical conductor wherein : the first electrical conductor is electrically coupled to the second wall of the enclosure at a first end of the second conductor arrangement; the second electrical conductor is electrically coupled to the second applicator at the first end of the second conductor arrangement; and the first electrical conductor is electrically coupled to the second electrical conductor at a second end of the second conductor arrangement, where the first end of the second conductor arrangement is opposite the second end of the second conductor arrangement.

[0017] In one or more embodiments, the electrical distance from a point of contact between the first electrical conductor and the second wall of the enclosure and a point of contact between the second electrical conductor and the second applicator may be an integer multiple of the first wavelength ±20%.

[0018] In one or more embodiments, the second conductor arrangement may comprise a second impedance matching circuit between the first electrical conductor and the second electrical conductor wherein the second impedance matching circuit is configured to tune the electrical distance through the second conductor arrangement such that the electrical distance is an integer multiple of the first wavelength ±20%.

[0019] In one or more embodiments, the second conductor arrangement may comprise a second coaxial cable and wherein: the first electrical conductor is one of an electrically conductive sheath and an electrically conductive core of the coaxial cable; and the second electrical conductor is the other of the electrically conductive sheath and the electrically conductive core of the coaxial cable.

[0020] In one or more embodiments, the second conductor arrangement may comprise a plurality of coaxial cables and the second coaxial cable is one of the plurality of coaxial cables of the second conductor arrangement, wherein each coaxial cable comprises a respective electrically conductive sheath and a respective electrically conductive core and wherein, for each of the plurality of coaxial cables: one of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second wall of the enclosure at the first end of the coaxial cable; the other of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second applicator at the first end of the coaxial cable; and the electrically conductive sheath is electrically coupled to the electrically conductive core at a second end of the coaxial cable, where the first end of the coaxial cable is opposite the second end of the coaxial cable.

[0021] In one or more embodiments, the first applicator may comprise a first electrically conductive plate and the second applicator comprises a second electrically conductive plate and wherein the receipt of the first oscillating current by the first electrically conductive plate and the second oscillating current by the second electrically conductive plate results in the oscillating electric field between the first metallic plate and the second metallic plate.

[0022] In one or more embodiments, each wall of the enclosure may be electrically conductive.

[0023] In one or more embodiments, the first frequency of the first oscillating current and the second oscillating current may be 100 MHz - 600 MHz.

[0024] In one or more embodiments, the first frequency of the first oscillating current and the second oscillating current may be 120 - 150 MHz.

[0025] In one or more embodiments, the device may further comprise a dielectric sample container configured to close over the sample stage such that a sample received at the sample stage is enclosed by the dielectric sample container when the oscillating electric field is generated.

[0026] In one or more embodiments, the phase difference between the first oscillating current and the second oscillating current may be 180° ± 30°.

[0027] Brief Description of the Drawings

[0028] One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows an example embodiment of a device of the present disclosure;

[0029] Figure 2 shows another example depiction of a first oscillating current and a second oscillating current each having a first frequency;

[0030] Figure 3 shows another example embodiment of a device of the present disclosure;

[0031] Figure 4 shows another example method of a device of the present disclosure;

[0032] Figure 5 shows an example simulation of an electric field at the surface of a spherical dielectric material; and

[0033] Figure 6 shows a field strength cross-section of the dielectric material of figure 5.

[0034] Detailed Description

[0035] The present disclosure describes a device which is configured to rapidly heat a sample. The sample may be partially or wholly biological in nature and may be at least partially dielectric. As already discussed, there are several applications in which rapid and uniform thermal heating may be desirable.

[0036] Figure 1 shows an example device 100 which is configured to rapidly heat a sample 101. The device 100 comprises an enclosure 102 which itself comprises a plurality of electrically conductive walls. The enclosure 102 is configured and shaped to enclose various components of the device 100 therewithin. In one or more embodiments, each of the walls of the enclosure 102 may be electrically conductive, however, in other embodiments, only two or more of the walls may be electrically conductive. For example, the walls may be made out of a conductive metal such as copper, however, the walls may alternatively be made out of non-metallic conductors. It will be appreciated that while the enclosure 102 is depicted in figure 1 as being cuboid, this is not the only form that the enclosure 102 may take and, instead, the enclosure 102 may have any suitable number of walls which still provides for the functionality described herein.

[0037] The enclosure 102 comprises at least a first end wall 103 and a second end wall 104 wherein the first end wall 103 is arranged opposite the second end wall 104. In order to facilitate reference to the figures, the present disclosure regularly makes reference to points of contact at or through the first or second end walls. It will be appreciated, however, that the exact wall at or through which a particular connection is made may be unimportant. As such, the first and second end walls 103, 104 described herein may be replaced with any of the walls of the enclosure provided the selected walls provide for the functionality described herein. The enclosure 102 may further comprise a top wall and a bottom wall wherein the top wall is arranged opposite the bottom wall. The enclosure may further comprise a first side wall and a second side wall wherein the first side wall is arranged opposite the second side wall. It will be appreciated that the terms "end", "top", "bottom", and "side" are not to be considered limiting herein as to the orientation at which the device 100 must be placed in use. Instead, these are used as useful labels to assist in the visualisation of the device 100. Where walls are described as opposite one-another, this is intended to imply that the opposite walls are, or are substantially, parallel to each other.

[0038] The device 100 further comprises a first applicator 105 which is configured to receive a first oscillating current wherein the first oscillating current has a first frequency. The device 100 further comprises a second applicator 106 which is configured to receive a second oscillating current at the first frequency. The device 100 is configured such that the second oscillating current received by the second applicator 106 is out of phase with the first oscillating current received by the first applicator 105. By receiving out- of-phase oscillating currents, and thereby the different charges at the applicators 105, 106, a potential difference is generated between the applicators 105, 106 which thereby generates an oscillating electric field. It will be appreciated that an electric field may be most efficiently generated if the first applicator is arranged opposite the second applicator. Further, the first applicator may have substantially planar surface that is arranged opposite a planar surface of the second applicator. In other embodiments, however, the first and second applicators may have faces which are not planar. The frequency of the oscillating electric field is equal to, or substantially equal to, that of the first frequency of the first and second oscillating currents. The electric field further has a first wavelength which corresponds to the first frequency. That is, the first wavelength can be calculated from the first frequency. Thus, the first and second applicators 105, 106 may be considered as first and second electric field plates configured to generate an electric field therebetween.

[0039] The first frequency may be any frequency which is suitable to induce electric dipole heating in a sample within an oscillating electric field generated at least in part by the applicators 105, 106 which receive the first and second oscillating currents. For example, the first frequency may be 100 MHz - 600 MHz, 100 MHz - 300 MHz, 110 MHz - 200 MHz, 120 MHz - 150 MHz or, particularly, 136.6 MHz. It will be appreciated that, while these frequencies are provided as examples, other frequencies may also be able to achieve the same effect as that generally described herein and various factors may impact the precise frequency selected, such as sample type, sample size, enclosure size and other factors.

[0040] It will be appreciated that any phase difference between the first applicator 105 and the second applicator 106 will result in an electric field therebetween. In order to achieve a maximum possible electric field strength at a point directly between the first and second applicators when the respective first and second oscillating currents are at their respective maximum and minimum values, the phase difference may preferably be 180°. It will be appreciated that it may be impractical to consistently achieve a phase difference of exactly 180° and that some error may be acceptable in a practical device 100 which still results in an acceptable electric field between the first and second applicators. For example, the phase difference may be 150° - 210°, 160° - 200°, 170° - 190° or 175° - 185°. That is, the phase difference may be 180° ± 30°- 180° ± 20°- 180° ± 10°' 180° ± 5°.

[0041] The first applicator 105 may comprise a first electrically conductive plate / disc / or other planar surface. The first electrically conductive plate / disc / or other planar surface may be substantially planar and may extend parallel or substantially parallel to the first end wall 103. While the first applicator may be substantially planar in one or more embodiments, in other embodiments, the first applicator may have a different form, such as a cube, sphere, or other volume. Similarly, the second applicator may comprise a second electrically conductive plate / disc or other planar surface The second electrically conductive plate / disc or other planar surface may be substantially planar and may extend parallel or substantially parallel to the second end wall 104. While the second applicator may be substantially planar in one or more embodiments, in other embodiments, the second applicator may have a different form, such as a cube, sphere, or other volume.

[0042] The first oscillating current and the second oscillating current may be received from one of several different possible sources. In the embodiment depicted in figure 1, the first oscillating current may be received by the first applicator 105 from a first current generator 107 and the second oscillating current may be received by the second applicator 106 from a second current generator 108. A current generator 107, 108 may be any device 100 which is suitable to generate and deliver an oscillating current. As will be described further later in this text, the use of two current generators 107, 108 may be particularly challenging, as properly matching the necessary oscillating frequencies and phases may not be trivial. The current received by the first applicator 105 from the first current generator 107 may be received via an aperture in the first end wall wherein a conductor which transmits the current to the first applicator is electrically isolated from the first end wall. Similarly, the current received by the second applicator 106 from the second current generator 108 may be received via an aperture in the second end wall wherein a conductor which transmits the current to the second applicator is isolated from the second end wall.

[0043] In order to provide for impedance matching functionality, one or both of the first and second current generators 107, 108 may comprise or be coupled to a respective impedance matching apparatus (not shown) which is configured to adjust the impedance of the current generated by a respective current generator and provided to the applicators. The impedance matching apparatus may comprise one or more inductors or capacitors which are configured to adjust the effective electrical distance between its respective current generator 107, 108 and respective applicator 105, 106 such that the phase of the oscillating current can be tuned as desired. The impedance matching apparatus may be a fixed or variable impedance matching apparatus which either provides a corresponding fixed impedance or a variable impedance.

[0044] The impedance matching apparatus may comprise a conductive sheet arranged to surround the impedance matching unit, wherein the conductive sheet is in electrical contact with the enclosure and grounded in the first current generator. At least one capacitor of the impedance matching apparatus may be coupled between the conductive sheet and a conductor that couples the first oscillating current generator to the first applicator. The capacitive coupling of the conductor to the enclosure via the capacitor arranged therebetween may allow for the impedance matching apparatus to provide for impedance matching of the enclosure and may further provide for the 180° phase difference between the currents received by the first and second applicators 105, 106. At least one of an inductor and a capacitor may be coupled in series with the conductor which conducts the oscillating current going to the first applicator which may provide for the impedance matching functionality for the first applicator 105.

[0045] One or both of the first current generator 107 and the second current generator 108 is configured to be grounded via the electrically conductive walls of the enclosure 102. That is, the flow of current from one or both of the generators 105, 107 to ground may have, as part of its path, the conductive walls of the enclosure 102. The effect of having a current flow through the conductive walls of the enclosure 102 is that a further oscillating electric field is generated which enhances the response by the sample 101 and, thereby, enhances the heating applied to the sample 101. It has been found that the further oscillating field constructively interacts with the oscillating electric field generated by the first and second applicators 105, 106 in order to provide an enhanced oscillating electric field within the enclosure 102.

[0046] While the embodiment of figure 1 shows a single pair of applicators 105, 106, the device 100 may comprise two, three or any other plurality of pairs of applicators wherein each pair of applicators has the functionality and form described above. The use of additional pairs of applicators may allow for a higher electric field density to be generated at the sample thereby resulting in an increased rate of heating. Additional pairs of applicators may also be provided and configured in order to increase the oscillating electric field homogeneity in order to provide for more even heating of the sample. Where a plurality of pairs of applicators are used, two or more of the plurality of pairs of applicators may use different frequencies to generate their oscillating electric fields. For example, the first pair of applicators 105, 106 may use an oscillating current at a first frequency while a second pair of applicators (not shown) may use an oscillating current at a second frequency wherein the second frequency is different to the first frequency.

[0047] The device 100 further comprises a sample stage (not shown) arranged between the first applicator 105 and the second applicator 106 within the enclosure 102. The sample stage is configured to receive the sample 101 intended for heating. The sample stage may be any suitable platform or mounting apparatus for holding, containing or supporting a sample 101 for heating. The sample stage may be as simple as a surface of the bottom wall of the enclosure which is positioned between the first and second applicators 105, 106. In other embodiments, the sample stage may be a clamp or other device for holding the sample at a desired location within the enclosure 102 where the desired location may be selected to be an optimum point within the enclosure 102 for heating.

[0048] The device 100 may further comprise a dielectric sample container (not shown) configured to be received at the sample stage such that a sample received at the sample stage is enclosed by the dielectric sample container when the oscillating electric field is generated. The dielectric sample container may be placed on the sample stage, be held in position by the sample stage or close over the sample stage. The dielectric sample container may be cuboid or it may have another form. The dielectric sample container may be shaped to close over the sample 101 placed at the sample stage, thereby enclosing the dielectric sample by way of contact with the sample stage. In one or more alternative embodiments, the dielectric sample container may be configured to receive a sample 101 therewithin and close over the sample with a door, flap or other suitable closure. The dielectric sample container may comprise one or more different materials wherein at least one material may have a dielectric constant from 65 to 90.

[0049] The longest electron path between two points on the walls of the enclosure that electrons may travel in a single cycle of the oscillating current may be equal to N / 2 multiplied by the first wavelength ±20% wherein N is an odd integer. It will be appreciated that the two points which would have the longest path that electrons could travel across during the course of a phase cycle (a single cycle of the AC current) would be two points at a same end of the enclosure, i.e., from one end of the enclose to the opposite and back again. For example, where the enclosure is an elongate enclosure (having two pairs of opposing sides of equal or substantially equal length), the longest path between two points may be a point starting from one corner of one of these elongate walls to an opposing corner of that wall and then a corresponding path back along the same path or along a diagonal of the elongate wall adjacent to the first elongate wall. For example, where the enclosure is cuboid, the distance between the diagonal of the two longest adjacent walls of the disclosure may represents the longest path which the electronics could travel. The sum of the lengths of these two diagonals may be equal to N multiplied by the first wavelength ±20% wherein N is an odd integer. In other embodiments, the error may be ±10%, ±5% or ±1%. That is, the longest path between two points on the walls of the enclosure may be, for example, one wavelength, three wavelengths, five wavelengths, etc. This may be particularly advantageous, as the further oscillating electric field generated by current flow in the electrically conductive walls may have a maximum field strength when the longest electron path travelled between two points on the walls of the enclosure during a single cycle of the oscillating current is equal to N multiplied by the first wavelength ±20% wherein N is an odd integer. Correspondingly, the longest distance travelled by electrons during a half-cycle of the oscillating current from a first end of the enclosure 102 to the opposite end of the enclosure 102 (but not back) may be equal to N / 2 multiplied by the first wavelength ±20% wherein N is an odd integer.

[0050] Figure 2 shows an example of how the first oscillating current, Al, may vary at the first applicator and how the second oscillating current, Bl, may vary at the second applicator. The oscillating electric field generated by these oscillating currents causes charged and polar molecules in the dielectric material to change orientation to align with the electric field. This realignment of the molecules (push-pull of the molecules) causes the dielectric material to heat in a process known as dielectric heating. The electric field generated by additional electric field generated by movement of charge through the walls of the enclosure provides for enhanced heating compared to typical capacity heating techniques. For example, if there is a relative positive charge at the first applicator and a relative negative charge at the second applicator, then a relative negative charge will also be present in the conductive walls of the enclosure, thereby providing for an enhancement of the field at the sample.

[0051] Figure 3 shows an alternative embodiment of the device 300 of the present disclosure. Any common features, such as the sample stage, the applicators 104, 105, the impedance matching apparatus 301 (one in this case) and the enclosure will not be redescribed in detail and are as described in reference to figure 1 except where indicated. Thus, it will be understood that the disclosures provided above with reference to these features are equally applicable to the embodiments described with reference to figure 2 and further embodiments. Further, where two components are represented in an equivalent or like-manner between figures 1 and 3, the same reference numerals will be used so that features which differ in figure 3 are more easily identified.

[0052] In the embodiment of figure 3, a single current generator 302 is used to generate the first oscillating current which is applied to the first applicator 105. That is, a second current generator is not required. As has already been described, the impedance matching apparatus 301 may capacitively couple a current received from the current generator 302 to a conductive sheet which itself is electrically coupled to the first enclosure which allows for impedance matching of the enclosure and the second applicator. As a result of the capacitive coupling of the conductor which connects the current generator 302 to the first applicator 105 to the enclosure 102, the phase of the ground current via the conductive walls may be 180°, or substantially 180° out of phase with the first oscillating current received by the first applicator 105. It will be appreciated that the same effect or substantially the same effect may be achieved if the phase difference is not exactly 180°. For example, the phase difference may be 180°±30%, 180°±20%, 18O°±1O%,18O°±5% or 18O°±1%.

[0053] In the embodiment of figure 3, the first applicator 105 may be coupled to the first current generator 302 (which may be the only current generator in such an embodiment unless there are multiple pairs of applicators) via a first conductor arrangement 303. The first conductor arrangement 303 may extend through the first end wall 103 at a first aperture such that the first applicator 105 can receive the oscillating current from the first current generator 302 external to the enclosure 102 via the impedance matching apparatus 301. It will be appreciated that the first conductor arrangement may extend through a wall other than the first end wall in some embodiments and that the first end wall is depicted as an example only for ease of description.

[0054] In one or more embodiments, the first conducive arrangement 303 may comprise a first coaxial cable wherein the first coaxial cable comprises a first electrically conductive sheath and a first electrically conductive core within and electrically insulated from the electrically conductive sheath.

[0055] In one or more embodiments, such as that depicted in figure 3, the device 100 may further comprise a second conductor arrangement 304 which electrically couples the second applicator 106 to the second end wall 104. The second conductor arrangement 304 may comprise a first electrical conductor 305 and a second electrical conductor 306 wherein the first electrical conductor 305 is electrically coupled to the second side wall 104 of the enclosure 102 at a first end of the second conductor arrangement 304. The second electrical conductor 306 may be electrically coupled to the second applicator 106 at the first end of the second conductor arrangement 304. Finally, the first electrical conductor 305 may be electrically coupled to the second electrical conductor 306 at a second end of the second conductor arrangement 304, where the first end of the second conductor arrangement 304 is opposite the second end of the second conductor arrangement 304. Thus, as depicted in figure 3, the second conductor arrangement 304 may form a conductive path between the second end wall 104 and the second applicator 106. In one or more embodiments, the first electrical conductor 305 and second electrical conductor 306 may be different portions of the same conductive component, such as a conductive wire or cable. In other embodiments, the first and second electrical conductors 305, 306 may be different conductive components which are electrically connected at the second end of the second conductor arrangement 304.

[0056] The electrical distance from a point of contact between the first electrical conductor 305 and the second side wall 104 of the enclosure 102 and a point of contact between the second electrical conductor 306 and the second applicator 106 may be an integer multiple of the first wavelength. That is, the electrical distance may be one, two, three, five or more integer multiples of the first wavelength. In this way, the phase of the oscillating current at the second applicator 106 may be the same as the phase of the oscillating current at the second end wall 104.

[0057] The second conductor arrangement 304 of the device 100 may further comprise a second impedance matching apparatus (not shown) arranged between the first electrical conductor 305 and the second electrical conductor 306. The second impedance matching apparatus may be configured to tune the electrical distance through the second conductor arrangement 304 such that the electrical distance is an integer multiple of the first wavelength. That is, the physical length of the first and second electrical conductors 305, 306 may not be the sole determiners of the electrical length between the second side wall 104 and the second applicator 106. As with the first impedance matching apparatus, the second impedance matching apparatus may comprise one or more capacitors and / or inductors which are capable of adjusting the electrical length in question. The second impedance matching apparatus may provide for fixed or variable impedance matching.

[0058] By electrically connecting the second applicator 106 to the conductive walls of the enclosure 102 where the first current generator 302 is also grounded via the conductive walls of the enclosure 102, the current provided to the first applicator 105 by the first current generator 302 is able to drive an oscillating current at the second applicator 106. That is, in such embodiments, the source of the second oscillating current is the same as the source of the first oscillating current and the phase difference between the first oscillating current is controlled to be out of phase with the phase of the first oscillating current by way of carefully controlling the electrical lengths of the enclosure 102, the first conductor arrangement 303 and the second conductor arrangement 304 both by controlling their physical lengths and their electrical lengths using impedance matching apparatuses. In particular, by providing a second conductor arrangement

[0059] 304 which has an electrical length of an integer multiple wavelength and an enclosure which is 180° out of phase with the first applicator 105, a phase difference of 180° (within acceptable error bounds already discussed) can be maintained between the oscillating currents at the first and second applicators 105, 106. This phase difference is achieved without the need for separate current generators which may interfere with one-another which can make maintaining a consistent phase difference challenging.

[0060] Figure 4 shows a further embodiment of a device 400 according to the present disclosure. Any common features, such as the sample stage, the applicators 105, 106, the impedance matching apparatus 301 and the enclosure 102 will not be redescribed and are as described in reference to figure 1 except where indicated. Further the first conductor arrangement 303 is as described with reference to figure 3. As is described further below, the second conductor arrangement described with reference to figure 3 comprises a coaxial cable in this embodiment and may take the form of one or more coaxial cables in further embodiments.

[0061] In one or more embodiments, such as that of figure 3, the second conductor 304 arrangement 106 comprises a second coaxial cable 401. The first electrical conductor

[0062] 305 of the second conductor arrangement 304 may be one of an electrically conductive sheath 402 and an electrically conductive core 403 of the second coaxial cable 401. Further, the second electrical conductor 306 may be the other of the electrically conductive sheath 402 and the electrically conductive core 403 of second coaxial cable 401. It will be appreciated that it does no matter which of the sheath 402 and the core 403 corresponds to the first electrical conductor 305 and which corresponds to the second electrical conductor 306. As was described with reference to the first coaxial cable which couples the first current generator 302 and the first applicator 105, the sheath 402 and the core 403 are substantially interchangeable in terms of which components they are connected to as long as they, in this case, provide for a conductive path between the second end wall 103 of the enclosure 102 to the second applicator 106. The electrical path is formed by providing for a short between the electrically conductive sheath 402 and the electrically conductive core 403 of the second coaxial cable at its second end, which is distal to the second end wall and the second applicator. The one of the sheath 402 and the core 403 which is connected to the second end wall may do so on an outer surface of the second end wall 103. The second coaxial cable 401, or a portion thereof, may pass through the second end wall 103 to couple with the second applicator 106. By way of example, the sheath 402 of the second coaxial cable may couple to the second end wall 103 while the core of the second coaxial cable 401 may pass through the second end wall 103 in order to couple with the second applicator 105. In such embodiments, the conducting member (sheath 402 or core 403) which is connected directly to the applicator may be electrically insulated from the second end wall 104 such that a short is not formed between the second end wall 103 and the second applicator 106, as this would cause the phase applied by the second applicator 106 to not be the desired phase.

[0063] A second impedance matching apparatus (not shown) may be placed between the electrically conductive sheath 402 and the electrically conductive core 403 of the second coaxial cable 401 in order to provide for required impedance matching to achieve a desired phase at the second applicator.

[0064] In one or more embodiments, the second conductor arrangement 304 may comprise a plurality of coaxial cables, wherein the plurality of coaxial cables comprised by the second conductor arrangement includes the second coaxial cable 304. Each coaxial cable of the plurality of coaxial cables may comprise a respective electrically conductive sheath and a respective electrically conductive core. For each of the coaxial cables: one of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second side wall of the enclosure at the first end of the coaxial cable; the other of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second applicator at the first end of the coaxial cable. Further, the electrically conductive sheath may be electrically coupled to the electrically conductive core at a second end of the coaxial cable, where the first end of the coaxial cable is opposite the second end of the coaxial cable. All of this is to say that the plurality of coaxial cables may be arranged in a plurality of different ways such that they achieve parallel coupling of the second end wall to the second applicator. Using a plurality of parallel coaxial cables may allow for higher power transfer to be achieved.

[0065] It has been found that the described device can generate heat in a load rapidly and with great homogeneity. For example, slabs of meat exceeding one kilogram have been cooked quickly and homogeneously. In fact, it has further been shown that meat can be cooked to a higher temperature at its centre than at its periphery. The device may also be used for rapidly thawing frozen organs intended for transplantation without tissue bursts due to ice formation in the blood vessels or for homogeneous thawing of frozen blood serum and frozen living cells without using a field equaliser. As discussed further above, the device may also be used for the preparation or thawing of foodstuffs.

[0066] Figure 5 shows a computer simulation of the field on the surface of a 500 gram sphere with the same dielectric properties as raw pork. Figure 6 shows that the field strength is higher in the middle of the dielectric load (500 grams of park) compared with the field strength on the surface. The field strength corresponds to the temperature development in the load. The simulation result was verified by a warming experiment of 600 grams of pork. The starting temperature was 5°C. After 10 minutes, the temperature in the centre of the load increased to approximately 65°C while, at the same time, the surface temperature was in the interval of 7°C - 15°C.

[0067] It will be appreciated that various features described with reference to various embodiments hereinabove that are not explicitly contradictory may be combined to form additional embodiments. That is, the above embodiments do not represent every possible permutation of features, as to do so would be prohibitive, however, it will be understood that this does not prohibit the combination of disclosed features which fall within the scope of the claims. The scope of protection is defined as laid out in the claims and the skilled person will understand the various combinations of features that are described herein and that would fall within the scope of the claims.

Claims

CLAIMS1. A device for heating a sample comprising: an enclosure comprising a plurality of electrically conductive walls; a first applicator configured to receive a first oscillating current at a first frequency; a second applicator configured to receive a second oscillating current at the first frequency wherein the second oscillating current is out of phase with the first oscillating current, and wherein, due to the phase difference between the first and second oscillating currents, the device is configured to generate an oscillating electric field between the first applicator and the second applicator at a first wavelength corresponding to the first frequency, wherein one or both of the first applicator and the second applicator is configured to be grounded via the electrically conductive walls of the enclosure such that the passage of current through the walls of the enclosure generates a further oscillating electric field and wherein the enclosure is configured to receive the sample at a sample stage arranged between the first applicator and the second applicator within the enclosure.

2. The device of claim 1 wherein a longest electron path that electrons travel in a single cycle of the oscillating current between two points on the walls of the enclosure may be equal to N multiplied by the first wavelength ±20% wherein N is an odd integer.

3. The device of any preceding claim wherein the first applicator is coupled to a current generator which is configured to generate the first oscillating current.

4. The device of claim 3 further comprising an impedance matching apparatus configured to provide for impedance matching between the current generator, the first applicator, the enclosure and the second applicator.

5. The device of any of claims 3 or 4 wherein the first applicator is coupled to the current generator via a first conductor arrangement and the impedance matching apparatus, wherein the first conductor arrangement extends through a first wall of the enclosure at a first aperture and wherein the first conductor arrangement is electrically insulated from the wall through which it extends.

6. The device of claim 5 wherein the impedance matching apparatus comprises a conductive sheet arranged to surround components of the impedance matchingapparatus, wherein the conductive sheet is in electrical contact with the enclosure and grounded in the first current generator, the first impedance matching apparatus may comprise at least one capacitor which is coupled between the conductive sheet and the first conductor apparatus and least one of an inductor and a capacitor which is coupled in series with the first conductor arrangement.

7. The device of any preceding claim wherein the second applicator is electrically coupled to a wall of the enclosure.

8. The device of any of claims 3 to 7 wherein the second applicator is electrically coupled to a second wall of the enclosure via a second conductor arrangement comprising a first electrical conductor and a second electrical conductor wherein: the first electrical conductor is electrically coupled to the second wall of the enclosure at a first end of the second conductor arrangement; the second electrical conductor is electrically coupled to the second applicator at the first end of the second conductor arrangement; and the first electrical conductor is electrically coupled to the second electrical conductor at a second end of the second conductor arrangement, where the first end of the second conductor arrangement is opposite the second end of the second conductor arrangement.

9. The device of claim 8 wherein the electrical distance from a point of contact between the first electrical conductor and the second wall of the enclosure and a point of contact between the second electrical conductor and the second applicator is an integer multiple of the first wavelength ±20%.

10. The device of claim 9 wherein the second conductor arrangement comprises a second impedance matching circuit between the first electrical conductor and the second electrical conductor wherein the second impedance matching circuit is configured to tune the electrical distance through the second conductor arrangement such that the electrical distance is an integer multiple of the first wavelength ±20%.

11. The device of any of claims 8 - 10 wherein the second conductor arrangement comprises a second coaxial cable and wherein: the first electrical conductor is one of an electrically conductive sheath and an electrically conductive core of the coaxial cable; and the second electrical conductor is the other of the electrically conductive sheath and the electrically conductive core of the coaxial cable.

12. The device of claim 11 wherein the second conductor arrangement comprises a plurality of coaxial cables and the second coaxial cable is one of the plurality of coaxial cables of the second conductor arrangement, wherein each coaxial cable comprises a respective electrically conductive sheath and a respective electrically conductive core and wherein, for each of the plurality of coaxial cables: one of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second wall of the enclosure at the first end of the coaxial cable; the other of the respective electrically conductive sheath and the respective electrically conductive core is electrically coupled to the second applicator at the first end of the coaxial cable; and the electrically conductive sheath is electrically coupled to the electrically conductive core at a second end of the coaxial cable, where the first end of the coaxial cable is opposite the second end of the coaxial cable.

13. The device of any preceding claim wherein the first applicator comprises a first electrically conductive plate and the second applicator comprises a second electrically conductive plate and wherein the receipt of the first oscillating current by the first electrically conductive plate and the second oscillating current by the second electrically conductive plate results in the oscillating electric field between the first metallic plate and the second metallic plate.

14. The device of any preceding claim wherein each wall of the enclosure is electrically conductive.

15. The device of any preceding claim wherein the first frequency of the first oscillating current and the second oscillating current is 100 MHz - 600 MHz.

16. The device of claim 15 wherein the first frequency of the first oscillating current and the second oscillating current is 120 - 150 MHz.

17. The device of any preceding claim further comprising a dielectric sample container configured to close over the sample stage such that a sample received at the sample stage is enclosed by the dielectric sample container when the oscillating electric field is generated.

18. The device of any preceding claim wherein the phase difference between the first oscillating current and the second oscillating current is 180° ± 30°.

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