Patch for applying to a user's skin

Abstract

A patch for applying to a user’s skin is claimed, the patch being for use with a dielectric barrier discharge (DBD) terminal 124. The patch comprises a dielectric cover 112 having an inner surface and

Description

A first aspect of the present invention provides a patch for applying to a user’s skin, the patch for use with a dielectric barrier discharge terminal, the patch comprising: a dielectric cover having an inner surface and an outer surface; and a support mechanism for supporting the dielectric cover to define an air cavity between the inner surface of the dielectric cover and the user’s skin when the patch is applied to the user’s skin, wherein the dielectric cover comprises a sealing mechanism for forming an air-tight contact between the outer surface of the dielectric cover and the dielectric barrier discharge terminal for generation of plasma within the air cavity. Due to the sealing mechanism forming an air-tight contact with the DBD terminal, the generation of plasma outside the patch is largely prevented. Thus, the safety of the plasma treatment may be improved. Plasma can be generated within the air cavity defined between the dielectric cover of the patch and the skin, and the plasma, and gaseous emissions (e.g., nitrous oxides (NOx) and ozone) and UV which may be produced by the plasma can be held within the air cavity. It will be appreciated that an air-tight contact may refer to an air-free contact, for example in which there is no (or negligible) air between the outer surface of the patch’s dielectric cover and the DBD terminal. Further, because the patch is for use with an (external) DBD terminal the safety and / or consistency / reliability of the plasma treatment may be improved, because the DBD terminal (which may be at a high voltage) may be external to, or separate from the patch. It will be appreciated that a DBD terminal may refer to one or more electrodes. A DBD terminal may refer to a combination of one or more electrodes and a dielectric layer, where the one or more electrodes may be covered with, or embedded within the dielectric layer. The electrodes may be separated from one another by the dielectric layer. The one or more electrodes may comprise one or more high voltage electrodes (which may be coupled to a high voltage power source) and / or one or more ground electrodes (which may be grounded). It will further be appreciated that the DBD terminal may be external to the patch (i.e., the DBD terminal and the patch may be entirely separate / separable from one another). For example, the DBD terminal may be within a plasma generating device. For example, the patch may be usable with known plasma generating devices. In some examples, the air-tight contact between the outer surface of the dielectric cover of the patch and the DBD terminal may be such that the outer surface of the dielectric cover covers an entire exposed surface (e.g., which is exposed to the air / to the outside of the plasma generating device) of the DBD terminal. For example, the air-tight contact may be formed between a dielectric layer of the DBD terminal and the outer surface of the patch’s dielectric cover. As plasma treatment may be for medical and / or cosmetic purposes, the patch may be referred to as a medical patch, or a cosmetic patch. A plasma treatment according to the present disclosure may comprise, when the DBD terminal is in air-tight contact with the outer surface of the dielectric cover, applying a high voltage to the DBD terminal (or to at least one of the electrodes within DBD terminal) to generate plasma within the air cavity. In some examples, the patch may comprise a skin-coupling adhesive for sealing the air cavity by creating an air-tight seal between the dielectric cover and the user’s skin when the patch is applied to the user’s skin. In this way, the plasma and the gaseous emissions (e.g., Nox and ozone) and UV which may be produced by the plasma can be kept within the air cavity, thus improving the safety of the plasma treatment. For example, gaseous emissions such as Nox and ozone may break down or degrade over time, and thus if the patch is removed a few minutes after the plasma treatment, there may be negligible gaseous emissions released from the patch. Additionally, or alternatively, plasma may be prevented from being applied to parts of the skin other than that which is the target of the plasma treatment. In some examples, the skin-coupling adhesive may be on an inner surface of the dielectric cover. In other examples, the skin-coupling adhesive may be located on another component of the patch (e.g., on a support structure which extends from the inner surface of the dielectric cover, as will be described below). In some examples, the support mechanism may comprise at least a part of the dielectric cover. In some examples, the support mechanism may comprise an intrinsic property of the dielectric cover. For example, the support mechanism may comprise a material of the dielectric cover. For instance, at least a part of the dielectric cover may be formed of a structural (e.g., rigid) material such that the dielectric cover defines an air cavity between the inner surface and the user’s skin when the patch is applied to the user’s skin. For example, the support mechanism may comprise a first part of the dielectric cover, where the first part of the dielectric cover may be nearer to an edge of the dielectric cover than a second part of the dielectric cover. The first part of the dielectric cover may be formed of a material that is more rigid than the second part of the dielectric cover. Alternatively, the entire dielectric cover may be formed of a material sufficiently rigid to define the air cavity when the patch is applied to the user’s skin and sufficiently flexible to allow variation of the air cavity’s volume. In some examples, the support mechanism may include a support structure extending from the inner surface of the dielectric cover. For example, the support structure may extend from the inner surface of the dielectric cover to the user’s skin when the patch is applied to the user’s skin. In this way, the support structure may enable formation of and / or maintenance of the air cavity. In some examples, the support structure may be annular. The support structure may have an annular cross section, e.g., as taken perpendicular to a patch axis. The patch axis may be perpendicular to the outer surface and the inner surface of the dielectric cover and may extend from the outer surface to the inner surface. Thus, the air cavity may be (at least partially) defined by an interior, or inner circumferential / perimetral surface of the support structure. As such, the dielectric cover may be supported more uniformly. In this way, more uniform plasma generation may be facilitated. In some examples, the support structure may be in the form of a mesh. In this way plasma may be more evenly applied across a surface of the skin and / or the plasma may be applied across the skin in a more focused manner. In some examples, the support structure may be compressible or elastic, for example such that the volume of the air cavity can be controlled by application of a force to the outer surface of the dielectric cover. In some examples, the support structure may be made of a foam material. In this way, the volume of the air cavity may be adjustable e.g., by moving the DBD terminal closer to the skin, and / or the distance of the DBD terminal from the skin may be adjustable. As such, there may be an improved control over the plasma treatment. In some examples, the support structure may be wedge-shaped, with the support structure tapering in thickness towards the edge of the dielectric cover. For example, the support structure may be thicker (e.g., as measured along the patch axis, or between the dielectric cover and the skin when the patch is applied to the skin) at an end closer to the centre of the dielectric cover and thinner at an end closer to the edge of the dielectric cover. In this way, the dielectric cover may be better supported. The dielectric cover may form a convex shape or a dome shape when the patch is applied to the skin. Alternatively, the dielectric cover may be flat when the patch is applied to the skin. For example, the dielectric cover may include a flat top surface where the flat top surface may be formed of a flexible non-stretchable film or a flexible stretchable film. In some examples, the patch may comprise a single support structure only, for example such that a single air cavity may be defined by an inner circumferential / perimetral surface of the support structure. In other examples, the patch may comprise a plurality of support structures. Any feature described with reference to a support structure is applicable also to examples where a plurality of support structures is provided and may be applicable to some or all of the support structures. It will thus be appreciated that each of the support structures may extend from the inner surface of the dielectric cover, and / or each of the support structures may be annular, and / or may have an annular cross section as taken perpendicular to the patch axis for example. As such, the air cavity may include a plurality of sub-cavities. For example, a plurality of sub-cavities may be defined by a respective plurality of adjacent pairs of support structures, each sub-cavity being defined (at least partially) between an inner circumferential / perimetral surface of a first support structure in the pair, and an outer circumferential / perimetral surface of a second support structure in the pair. In this way plasma may be more evenly applied across a surface of the skin and / or the plasma may be applied across the skin in a more focused manner. In some examples, a peripheral support structure (i.e., a support structure located closest to the edge of the dielectric cover) may be rigid. In this way, an outer edge of the patch may be rigid, and a support of the dielectric cover may be improved. As mentioned above, in some examples, the skin-coupling-adhesive may be located on the support structure. For example, the support structure may comprise a skin-facing surface which faces towards the skin (when the patch is applied to the user’s skin), and the skincoupling adhesive may be located on the skin-coupling surface of the support structure. In some examples, the skin-coupling adhesive may be located on a skin-facing surface of a peripheral support structure (i.e., the support structure located closest to the edge of the dielectric cover). In this way, the air cavity, defined (at least partially by) an inner circumferential / perimetral surface of the support structure, may be sealed. In other examples, the skin-coupling adhesive may be located on the inner surface of the dielectric cover and may extend around the support structure (e g., the peripheral support structure). The skin-coupling adhesive may alternatively be adjacent to or may border the support structure (e.g., the peripheral support structure). In this way, the air cavity may be sealed. For example, the skin-coupling adhesive may extend circumferentially around the support structure. For example, a perimeter of the skin-coupling adhesive may define a circle. In this way, the sealing of the air cavity may be improved. For example, a better seal may be achieved by an adhesive with a shape which includes no corners. Further, the dielectric cover may form a dome shape when the patch is applied to the skin. In other examples, the skin-coupling adhesive may take other shapes, e.g., a perimeter of the skin-coupling adhesive may define a triangle or a rectangle or any other odd shape which may be placed on a user’s face, for example. In some examples, the dielectric cover may have a circular cross section, as taken perpendicular to the patch axis. In some examples, at least a part of the dielectric cover may be formed of an elastic material that can conform to the shape of the DBD terminal when the DBD terminal is brought into contact with the outer surface of the dielectric cover. In this way, the air-tight contact between the dielectric cover and the DBD terminal may be improved and / or achieved. Thus, the sealing mechanism may comprise an intrinsic property of the dielectric cover, such as the material from which the dielectric cover is formed. Additionally, or alternatively, the elastic material may mean that the volume of the air cavity may be adjustable e.g., by moving the DBD terminal closer to the skin, and / or the distance of the DBD terminal from the skin may be adjustable. As such, there may be an improved control over the plasma treatment. Additionally, or alternatively, the elastic material may mean that use of the patch on different areas of the skin (e.g., on different areas of the face) can be facilitated. In some examples, at least a part of the dielectric cover may be non-elastic or non-stretchable. In some examples, the sealing mechanism may comprise an outer adhesive layer on the outer surface of the dielectric cover. The outer adhesive layer may be capable of adhering the plasma treatment device to the outer surface of the dielectric cover. In this way, the air-tight contact between the dielectric cover and the DBD terminal may be improved and / or achieved. In some examples, the sealing mechanism may comprise a mechanical coupling arrangement such as a screw or clip for coupling the dielectric cover to the plasma treatment device. In some examples, the sealing mechanism may comprise a static coupling mechanism. In some examples, the sealing mechanism may comprise a magnetic coupling mechanism, which may include a magnet or magnetic material on a patch-facing surface (e.g., which includes the DBD terminal) of the plasma generating device, and a magnet or magnetic material of opposite polarity on the outer surface of the dielectric cover of the patch. In some examples, the sealing mechanism (e.g., the outer adhesive layer on the dielectric cover of the patch) may be weaker (e.g., may have a lower adhesive strength) than the skin-coupling adhesive. In some examples, the outer adhesive layer on the dielectric cover of the patch may have a smaller cross-sectional area (e.g., as taken perpendicular to the patch axis) than that of the skin-coupling adhesive. In this way, the DBD terminal may be detached from the patch without detaching the patch from the skin. In some examples, the adhesion between the plasma generating device and the outer adhesive layer on the dielectric cover of the patch may be weaker than the adhesion between the skin-coupling adhesive and the skin, when the patch is applied to the skin. In this way, the DBD terminal may be detached from the patch without detaching the patch from the skin. As discussed above, because the patch according to the present disclosure is for use with an (external) DBD terminal, the safety and / or consistency / reliability of the plasma treatment may be improved, because the DBD terminal (which may be at a high voltage) may be external to, or separate from the patch. Thus, in some examples, the patch may include no electrodes. Such a patch may be referred to as a “dummy patch” and may include only dielectric and / or insulating materials. In this way, in addition or alternatively to the safety benefits, such a patch may be cheaper to manufacture and / or may be more environmentally friendly, for example, when the patch corresponds to a disposable patch. When the patch includes no electrodes, the patch may be for use with a plasma treatment device that includes a DBD terminal comprising only a single electrode covered with a dielectric layer, the electrode being coupled to a high voltage power source. In this case, the plasma treatment may correspond to a VDBD plasma treatment, where the skin itself may act as the second electrode, or second DBD terminal in the VDBD setup. When the patch includes no electrodes, the patch may additionally, or alternatively be for use with a plasma treatment device that includes a DBD terminal comprising two electrodes embedded within and separated by a dielectric layer, one electrode being coupled to a high voltage power source, and the other being grounded. In this case, the plasma treatment may correspond to a SDBD plasma treatment. In other examples, the patch may comprise one or more electrodes on the outer surface of the dielectric cover. The patch may further comprise an electrical connector electrically coupled to the one or more electrodes, the electrical connector for electrically coupling the one or more electrodes to the plasma generating device that includes the (external) DBD terminal. The electrical connector may be for electrically coupling the one or more electrodes to the plasma generating device such as to ground the electrode(s). Thus, the safety of the plasma treatment may be improved, because the high voltage DBD terminal may be external to, or separate from the patch. When the patch includes one or more electrode(s) on the outer surface, the patch may be for use with a plasma treatment device that includes a DBD terminal comprising only (one or more) high voltage electrode(s) covered with a dielectric layer. In this case, the plasma treatment may correspond to a SDBD plasma treatment, where the electrode(s) on the outer surface of the dielectric cover forms the second electrode, or second DBD terminal in the SDBD setup. It will be appreciated that the patch may comprise only ground electrode(s). VDBD plasma treatment may be a more effective plasma treatment for certain applications. In some examples, the dielectric cover may have a thickness of no more than 2000 microns, for example no more than 200 microns. It will be appreciated that a thickness may refer to a size along a direction parallel to the patch axis. In this way, the dielectric cover may have limited impact on the plasma generation. In some examples, the dielectric cover may have a thickness of at least 20 microns. In this way, ease of manufacture and / or use of the patch (e.g., attaching the patch to the user’s skin) may be improved. In some examples, the thickness of the support structure may be at least 0.1 mm, for example at least 0.5 mm, and / or no more than 10 mm, for example no more than 8 mm, or no more than 1.5 mm. For example, when the patch is for use in SDBD plasma treatment, a thickness of the support structure may be no more than 10 mm, and / or when the patch is for use in VDBD plasma treatment, a thickness of the support structure may be no more than 8 mm. In a VDBD plasma treatment, the larger the gap between the DBD terminal and the skin and / or the thicker the dielectric cover, the higher the voltage required to be applied to the DBD terminal to generate plasma within the air cavity. In the SDBD setup, the size of the gap between the DBD terminal and the skin does not affect the plasma generation. Nonetheless, the thicker the dielectric cover, the higher the voltage required to be applied to the DBD terminal to generate plasma within the air cavity. In some examples, the thickness of the skin-coupling adhesive may be no more than 1000 microns, for example no more than 50 microns or no more than 5 microns, and / or at least 5 microns. Thus, in some examples, a total thickness of the patch may be at least 0.5 mm and / or no more than 10 mm, for example no more than 2 mm. In some examples, a diameter or diagonal width of the patch (e.g., a diameter or diagonal width of the cross-section of the patch perpendicular to the patch axis) may be at least 5 mm and / or no more than 200 mm, for example no more than 10 mm or no more than 5 mm. In this way, a cross-sectional area of the patch (e.g., taken perpendicular to the patch axis) may be larger than (e.g., at least double the size of) the cross-sectional area of a patchfacing surface of the plasma generating device (e.g., which includes the DBD terminal). As such, coupling of the device to the patch may be facilitated. In some examples, the dielectric cover may be formed of a polymer film. In some examples, the dielectric cover may be formed of polyurethane (PU), such as a polyurethane film. In this way, the patch may be stretchable and / or flexible, which may facilitate application of the patch to the user’s skin. In other examples, the dielectric cover may be formed of polypropylene, such as a polypropylene film. In other examples, the dielectric cover may be formed of thermoplastic polyreuthane (TPU), such as a thermoplastic polyreuthane film enabling static connection of the DBD terminal with the patch. In some examples, the patch may include a device contact on the outer surface of the dielectric cover. The device contact may be for contacting a contact sensor on the plasma generating device that includes the DBD terminal. In this way, the plasma generating device may detect whether the DBD terminal of the plasma generating device is in contact with the patch. In some examples, the device contact may be a conductive contact, which may be for electrically contacting a contact sensor on the plasma generating device. In some examples, the patch may include a plurality of device contacts on the outer surface of the dielectric cover. Any feature described with reference to a device contact is applicable also to examples where a plurality of device contacts is provided and may be applicable to some or all of the device contacts. In some examples, the plurality of device contacts may comprise an annular or circular array of device contacts. In this way, the plasma generating device may ensure a correct alignment of the DBD terminal with the patch. As such, generation of plasma outside of the patch may be prevented, and / or the safety of the plasma treatment may be improved. In some examples, the patch may include a skin contact on a skin-facing surface of the patch. The patch may further comprise an electrical connector electrically coupled to the skin contact, the electrical connector for electrically coupling the skin contact to the plasma generating device that includes the DBD terminal. In this way, the plasma generating device may detect whether the patch is coupled to the skin, and for example whether the air cavity is sealed. In some examples, the skin contact may be a conductive contact. In some examples, the patch may include a plurality of skin contacts on the skin-facing surface of the dielectric cover. Any feature described with reference to a skin contact is applicable also to examples where a plurality of skin contacts is provided and may be applicable to some or all of the skin contacts. In some examples, the plurality of skin contacts may comprise an annular or circular array of skin contacts. In some examples, the patch may include an alignment structure on the outer surface of the dielectric cover for coupling to a complementary alignment structure on the patch-facing surface of the plasma generating device. For example, the alignment structure may have a stepped shape for coupling to a complementary stepped shape. The alignment structure may have an annular cross section (e.g., as taken perpendicular to the patch axis). A second aspect of the present invention provides a plasma generating device for use with a patch according to the first aspect of the invention, where the plasma generating device may include a high voltage power supply, a dielectric barrier discharge terminal comprising an electrode electrically coupled to the high voltage power supply and a controller operable to control the high voltage power supply. Optionally, the plasma generating device may further include a contact sensor electrically coupled to the controller and configured to detect whether the dielectric barrier discharge terminal of the plasma generating device is in contact with the patch, where the controller may be configured to prevent the high voltage power supply from supplying power to the electrode when the contact sensor detects that the dielectric barrier discharge terminal is not in contact with the patch. In this way, a safety of the plasma generating device may be improved, because the plasma generating device may be inhibited or prevented from turning on (e.g., prevented from applying a voltage to the DBD terminal) when the plasma generating device is not in contact with the patch. As such, plasma may be inhibited or prevented from being generated outside of the patch. Such a device may be suitable for use by an untrained user, for example. To the extent that they are compatible, optional features set out above in relation to the first aspect may also be applied to the second aspect. For example, the contact sensor may be configured to detect whether the DBD terminal is in contact with the outer surface of the dielectric cover, and the controller may be configured to prevent the high voltage power supply supplying power to the electrode when the contact sensor detects (or in response to the contact sensor detecting) that the dielectric barrier discharge terminal is not in contact with the outer surface of the dielectric cover. In some examples, the contact sensor may comprise a conductive sensor. In this way, for example, the contact sensor may be able to detect whether the DBD terminal is in contact with the patch (e.g., the outer surface of the dielectric cover) by measuring a conductivity. For example, the contact sensor may be able to detect whether the DBD terminal is in contact with the patch or the skin, because the patch and the skin may have different conductivities. For example, the skin may be more conductive than the dielectric cover. The controller may be configured to prevent the high voltage power supply supplying power to the electrode when the contact sensor detects (or in response to the contact sensor detecting) that the DBD terminal is in contact with the skin. In some examples, the contact sensor may be for coupling to a respective device contact on the outer surface of the dielectric cover. In some examples, the plasma generating device may comprise a plurality of contact sensors electrically coupled to the controller. Any feature described with reference to a contact sensor is applicable also to examples where a plurality of contact sensors is provided and may be applicable to some or all of the contact sensors. It will thus be appreciated that the controller may be configured to prevent the high voltage power supply supplying power to the electrode when one or more of the contact sensors detects that the DBD terminal is not in contact with the patch (e.g., a device contact of the patch). In some examples, the plurality of contact sensors may comprise an annular circular array of contact sensors, which may extend around the DBD terminal. In this way, a correct alignment of the DBD terminal with the patch can be ensured. As such, a more even plasma generation and / or plasma distribution may be achieved within the patch. In some examples, the high voltage power supply may be operable in a plurality of power modes. For example, each power mode may be associated with a predetermined magnitude of the voltage supplied to the electrode. In some examples, the controller may be configured to detect a number of contact sensors which are coupled to respective device contacts of the patch, and may further be configured to change a power mode of the power supply (e.g., a magnitude of the voltage supplied to the electrode) based on the detected number. For example, different patches may have different numbers of device contacts, In this way, the power mode of the high voltage power supply may be adjusted for different patches. In some examples, the controller may be configured to detect whether one or more skin contacts of the patch are coupled to the skin. For example, for each of the one or more skin contacts, the controller may receive a contact signal via an electrical connector of the patch, the electrical connector electrically coupled to the skin contact of the patch, and may detect, from the contact signal whether the skin contact of the patch is coupled to the skin. The controller may be configured to prevent the high voltage power supply from supplying power to the electrode in response to detecting that one or more of the skin contacts of the patch are not coupled to the skin. In this way, the plasma generating device may detect whether the patch is coupled to the skin, and for example whether the air cavity is sealed. As such, the safety of the device may be improved. In some examples, the DBD terminal may comprise a plurality of electrodes electrically coupled to the high voltage power supply. In this way, a more even plasma generation may be achieved within the patch. For example, an array of (e.g., smaller) electrodes may facilitate more even plasma generation as compared to a single (e.g., larger) electrode. In some examples, the DBD terminal may (e.g., only) comprise high voltage electrode(s) covered by or embedded within a dielectric layer and coupled to the high voltage power supply. For example, the DBD terminal may not include ground electrode(s). In this way, the plasma generating device may be for use with a patch that comprises no electrodes to generate plasma using VDBD, or with a patch that comprises one or more electrodes to generate plasma using SDBD. In some examples, the DBD terminal may additionally comprise one or more ground electrodes covered by or embedded within the dielectric layer and separated from the one or more high voltage electrodes by the dielectric layer. In this way, the plasma generating device may be for use with a patch that comprises no electrodes to generate plasma using SDBD. By having both electrodes for the SDBD setup within the device, the safety, consistency and / or reliability of the plasma treatment may be improved. Further, the electrodes may be more durable when they are within the plasma generating device as opposed to within the patch. In some examples, the electrode(s) within the DBD terminal (e.g., the high voltage electrode(s)) may have a pointed shape. For example, a point or comer of the electrode(s) may point towards the skin during the plasma treatment. The pointed electrode(s) may be embedded within the dielectric layer of the DBD terminal, for example. In this way, an effective plasma generation area of the electrodes may be reduced. As such, the power required to generate the plasma may be reduced, and additionally, or alternatively the plasma generation may be more uniform. In some examples, the controller may further be configured to stop the high voltage power supply from supplying power to the electrode after a predetermined treatment duration. For example, the predetermined treatment duration may be at least 5 seconds and / or no more than 10 minutes. For example, the predetermined treatment duration may be 30 seconds. In some examples, a patch-facing portion of the plasma generating device (e.g., which comprises the DBD terminal) may be convex. In this way, an air-tight contact of the DBD terminal with the patch may be facilitated. In some examples, the plasma generating device may include an alignment structure on the patch-facing surface of the plasma generating device, for coupling to a complementary alignment structure on an outer surface of the patch’s dielectric cover. For example, the alignment structure may have a stepped shape for coupling to a complementary stepped shape. The alignment structure may extend, e.g., circumferentially, around the DBD terminal. A third aspect of the present invention provides a system for administering plasma to a user’s skin, the system comprising the patch according to the first aspect, and a plasma generating device. In more detail, the third aspect of the present invention provides a system for administering plasma to a user’s skin, the system comprising: a patch for applying to a user’s skin; and, a plasma generating device, wherein the plasma generating device comprises: a high voltage power supply; a dielectric barrier discharge terminal comprising an electrode electrically coupled to the high voltage power supply; and, wherein the patch comprises: a dielectric cover having an inner surface and an outer surface; and, a support mechanism for supporting the dielectric cover to define an air cavity between the inner surface of the dielectric cover and the user’s skin when the patch is applied to the user’s skin, wherein the dielectric cover comprises a sealing mechanism for forming an air-tight contact between the outer surface of the dielectric cover and the dielectric barrier discharge terminal of the plasma generating device. Thus, the sealing mechanism may be for generation of plasma within the air cavity, and / or may be for preventing the generation of plasma outside of the air cavity. It will be appreciated that any of the features, or any combination of the features described with reference to the first aspect of the disclosure are equally applicable to the third aspect. It will further be appreciated that the plasma generating device of the third aspect may correspond to the plasma generating device according to the second aspect. Thus, any of the features, or any combination of the features described with reference to first and second aspects of the disclosure are equally applicable to the third aspect. A fourth aspect of the present invention provides a cosmetic method for administering plasma to a user’s skin using the system of the third aspect. The method may comprise applying the patch to the user’s skin and sealing, via the skincoupling adhesive, the air cavity formed between the inner surface of the dielectric cover and the user’s skin (i.e., by creating an air-tight seal between the dielectric cover and the user’s skin via the skin-coupling adhesive of the patch). The method may further comprise applying the DBD terminal to the outer surface of the dielectric cover of the patch, and forming an air-tight contact between the DBD terminal and the outer surface of the dielectric cover via the sealing mechanism. The method may also comprise supplying, from the high voltage power supply, a high voltage to the DBD terminal of the plasma generating device. In this way, plasma may be generated within the air cavity. The method may also comprise detaching the plasma generating device from the patch. For example, the sealing mechanism may comprise an adhesive, which may be weaker than the skin-coupling adhesive, so the user can detach the plasma generating device from the patch by simply pulling the plasma generating device away from the patch. In this way, the plasma generating device may be detached from the patch, without detaching the patch from the skin. The method may comprise leaving the patch on the skin for a predetermined post-treatment duration (in which the plasma generating device may be turned off, and / or detached from the patch), which may be at least 30 seconds, for example at least 1 minute, or at least 2 minutes. In this way, there may be negligible gaseous emissions released from the patch. It will be appreciated that for each of the aspects of the disclosure, the examples provided may be combined in any suitable combination to provide further examples, except where such a combination is clearly impermissible or expressly avoided. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross-sectional side view of a patch with a single support structure and a plasma generating device with a single high voltage electrode. Figure 2 shows a cross-sectional side view of a patch with a plurality of support structures and a plasma generating device with a single high voltage electrode. Figure 3 shows a cross-sectional side view of a patch with a plurality of support structures and a plasma generating device with a single high voltage electrode. Figure 4 shows a cross-sectional side view of a patch and a plasma generating device with a plurality of high voltage electrodes. Figure 5 shows a cross-sectional side view of a patch and a plasma generating device with a plurality of ground electrodes and high voltage electrodes. Figure 6 shows a cross-sectional side view of a patch with a plurality of grounded electrodes and a plasma generating device with a plurality of high voltage electrodes. DETAILED DESCRIPTION Figure 1 shows a system 100 for administering plasma 102 to a user’s skin 104. The system 100 includes a plasma generating device 106 and a patch 108, which is shown applied to the user’s skin 104 over a target area 110 to be treated by the plasma 102 e.g., an area of inflammation or infection. The patch 108 is formed of an elastic dielectric cover 112 (e.g., formed of a polyurethane film), a support mechanism in the form of a support structure 114, and a skin-coupling adhesive 116. As shown in Figure 1, when the patch 108 is applied to the user’s skin 104, the support structure 114 extends from the inner surface of the dielectric cover 112 to the user’s skin 104 such as to define an air cavity 120 between the inner surface of the dielectric cover 112 and the user’s skin 104. The support structure 114 is annular in cross-section such that the air cavity 120 is partially defined by an inner circumferential surface of the support structure 114. The skin-coupling adhesive 116 is located on the inner surface of the dielectric cover 112, bordering and extending circumferentially around the support structure 114 such as to seal the air cavity 120. The skin-coupling adhesive 116 creates an airtight seal between the dielectric cover 112 and the user’s skin 104. Thus, when plasma 102 is generated within the air cavity 120, the plasma 102 and its by-products (e.g., Nox and UV) are held within the air cavity 120. A cross-sectional shape of the patch 108 (taken perpendicular to a “patch axis” extending from the outer surface to the inner surface of the patch 108) is circular. Due to the annular shapes of the support structure 114 and the skin-coupling adhesive 116, and due to tapering thickness of the support structure 114, when the patch 108 is applied to the user’s skin 104, the patch 108 forms a convex dome shape. Turning to the plasma generating device 106, as shown in Figure 1, the plasma generating device 106 includes a high voltage power supply 122, and a dielectric barrier discharge (DBD) terminal 124 formed of a single electrode 126 covered by a dielectric layer 128, with the electrode 126 being electrically coupled to the high voltage power supply 122. Although not shown in Figure 1, the plasma generating device 106 further comprises a controller operable to control the high voltage power supply 122. To begin the plasma treatment, the DBD terminal 124 of the plasma generating device 106 is brought into contact with the outer surface of the dielectric cover 112. To ensure that an air-tight contact is achieved between the DBD terminal 124 and the dielectric cover 112, the dielectric cover 112 includes a sealing mechanism. In the example shown in Figure 1, the sealing mechanism is achieved by virtue of the elastic material of the dielectric cover 112. The elastic material means that the dielectric cover 112 conforms to the shape of the DBD terminal 124. In other examples, the sealing mechanism may additionally / alternatively comprise an outer adhesive later on the outer surface of the dielectric cover 112. When the DBD terminal 124 is in airtight contact with the outer surface of the dielectric cover 112, a high voltage can be applied to the DBD terminal 124. Plasma 102 is then generated within the air cavity 120 via VDBD, where the skin 104 acts as the second electrode or second DBD terminal in the VDBD setup. As such, as shown in Figure 1, the plasma 102 is generated throughout the volume of the air cavity 120. Due to the airtight contact between the dielectric cover 112 and the DBD terminal 124, plasma 102 is prevented from being generated outside of the patch 108. In the example shown in Figure 1, the thickness of the dielectric cover 112 is no more than 200 microns, and thus the dielectric cover 112 has limited impact on the plasma generation. A further benefit of the elastic material of the patch 108 is that the distance of the DBD terminal 124 from the skin 104 can be adjusted during the plasma treatment. This is further enabled by virtue of the support structure 114 being formed of a compressible foam material. As the patch 108 includes no electrodes, the patch 108 is cheap to manufacture, safe to use and is more environmentally friendly. Due to being for use on a patient’s skin 104, the patch 108 is disposable. Although not shown in Figure 1, in some examples the plasma generating device 106 may include a contact sensor electrically coupled to the controller. The contact sensor is configured to detect whether the DBD terminal 124 is in contact with the outer surface of the dielectric cover 112, and the controller is configured to prevent the high voltage power supply 122 from supplying power to the electrode 126 in response to the contact sensor detecting that the DBD terminal 124 is not in contact with the outer surface of the dielectric cover 112. In this way, the safety of the plasma treatment may be further improved. However, it will be appreciated that this contact sensor is optional. Further, although in the example shown in Figure 1 the patch 108 includes only a single support structure 114, in other examples the patch includes a plurality of support structure 114, as shown in Figure 2. Figure 2 shows a system 200 for administering plasma 102 to a user’s skin 104. As will be appreciated, the system 200 shares several features in common with the system 100 shown in Figure 1. For example, the plasma generating device 106 is the same as the plasma generating device 106 shown in Figure 1. For conciseness, such features will not be described again. In the example shown in Figure 2, the patch 208 includes a plurality of support structures 114. Each of the support structures 114 is annular in cross-section and extend from the inner surface of the dielectric cover 112 to the user’s skin 104, such that sub-cavities 120a are defined between the various adjacent pairs of support structures 114. In this way plasma 102 may be more evenly applied across a surface of the skin 104 and / or the plasma 102 may be applied across the skin 104 in a more focused manner. Similar to the example shown in Figure 1, the skin-coupling adhesive 116 is located on the inner surface of the dielectric cover 112. In the example shown in Figure 2, the skin coupling adhesive 116 borders and extends around the peripheral support structure 114p (i.e., the support structure 114p located closest to the edge of the dielectric cover 112). Although in the examples shown in Figures 1 and 2 the skin-coupling adhesive 116 is located on the dielectric cover 112, in other examples the skin-coupling adhesive 116 may be located on another component of the patch, as shown in Figure 3, for example. Figure 3 shows a system 300 for administering plasma 102 to a user’s skin 104. As will be appreciated, the system 300 shares several features in common with the system 200 shown in Figure 2. For example, the plasma generating device 106 is the same as the plasma generating device 106 shown in Figure 2. For conciseness, such features will not be described again. The patch 308 shown in Figure 3 is different to that shown in Figure 2 in that the skincoupling adhesive 116 is located on a skin-facing surface of the peripheral support structure 114p. Figure 4 shows a system 400 for administering plasma 102 to a user’s skin 104. As will be appreciated, the system 400 shares several features in common with the system 100 shown in Figure 1. For example, the patch 108 shown in Figure 4 is the same as the patch 108 shown in Figure 1. For conciseness, such features will not be described again. The plasma generating device 406 of Figure 4 differs from that shown in Figure 1 in that the DBD terminal 424 comprises a plurality of electrodes 426 embedded within a dielectric layer 428. Each of the electrodes 426 is a high voltage electrode, being coupled to the high voltage power supply 122 within the plasma generating device 406. In this way, a more even plasma generation may be achieved within the patch 108. For example, an array of (e.g., smaller) electrodes may facilitate more even plasma generation as compared to a single (e.g., larger) electrode. The system 400 shown in Figure 4 operates similarly to that shown in Figure 1 in that plasma 102 is generated within the air cavity 120 via VDBD, where the skin 104 acts as the second electrode or second DBD terminal in the VDBD setup. In the example shown in Figure 4, the DBD terminal 424 in the plasma generating device 406 acts as the first DBD terminal 424 in the VDBD setup. As further shown in Figure 4, the high voltage electrodes 426 are pointed in shape such as to point towards the skin 104 during the plasma treatment. In this way an effective plasma generation area of the electrodes may be reduced. As such, the power required to generate the plasma may be reduced, and additionally, or alternatively the plasma generation may be more uniform. Although plasma 102 is generated by VDBD in the examples shown in Figures 1 to 4, in other examples, plasma 102 may be generated by SDBD. Figure 5 shows a system 500 for administering plasma 102 to a user’s skin 104. As will be appreciated, the system 500 shares several features in common with the system 400 shown in Figure 4, where like reference numbers have been used to denote features present in both figures. For example, the patch 108 shown in Figure 5 is the same as the patch 108 shown in Figure 4. The system 500 differs from that shown in Figure 4 in that the DBD terminal 524 within the plasma generating device 506 includes a plurality of ground electrodes 527 in addition to the plurality of high voltage electrodes 526. All of the electrodes 526, 527 are embedded within, and separate from one another by the dielectric layer 528. Due to the presence of the grounded electrodes, plasma 102 is generated within the air cavity 120 by SDBD. As such, as shown in Figure 5, the plasma 102 is generated on the inner surface of the dielectric cover 112. In other examples, plasma 102 may be generated within the air cavity 120 by SDBD by virtue of the patch comprising the ground electrodes 627, as shown in Figure 6. Figure 6 shows a system 600 for administering plasma 102 to a user’s skin 104, where the patch 608 includes a plurality of electrodes 627 on the outer surface of the dielectric cover 112. Each patch 608 is coupled to an electrical connector 630 which electrically couples the electrodes to a ground 632 of the plasma generating device 606. The plasma generating device 606 includes a DBD terminal 624 which comprises a plurality of electrodes embedded 626 within a dielectric layer 628. Each of the electrodes 626 within the plasma generating device 606 is a high voltage electrode, being coupled to the high voltage power supply 122 within the plasma generating device 606. Due to the presence of the grounded electrodes 627 in the patch 608, when a voltage is applied to the high voltage electrodes 626 in the plasma generating device 606, plasma 102 is generated within the air cavity 120 by SDBD. As such, as shown in Figure 6, the plasma 102 is generated on the inner surface of the dielectric cover 112. Whilst particular examples and embodiments have thus far been described, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the invention as defined by the claims. For example, the support structures 114 may be omitted and at least a part of the dielectric cover 112 5 may be formed of a sufficiently rigid material to support the dielectric cover 112, so as to define the air cavity 120 when the patch is in use.

Claims

1. A patch for applying to a user’s skin, the patch for use with a dielectric barrier discharge terminal,the patch comprising:a dielectric cover having an inner surface and an outer surface; and,a support mechanism for supporting the dielectric cover to define an air cavity between the inner surface of the dielectric cover and the user’s skin when the patch is applied to the user’s skin,wherein the dielectric cover comprises a sealing mechanism for forming an air-tight contact between the outer surface of the dielectric cover and the dielectric barrier discharge terminal for generation of plasma within the air cavity.

2. A patch according to claim 1 further comprising a skin-coupling adhesive for sealing the air cavity by creating an air-tight seal between the dielectric cover and the user’s skin when the patch is applied to the user’s skin.

3. A patch according to claim 1 or claim 2, wherein the support mechanism comprises at least a part of the dielectric cover.

4. A patch according to claim 1 or claim 2, wherein the support mechanism comprises a support structure extending from the inner surface of the dielectric cover.

5. A patch according to claim 4, wherein the support structure is annular.

6. A patch according to claim 4 or claim 5, wherein the support structure is compressible such that a volume of the air cavity can be controlled by application of a force to the outer surface of the dielectric cover.

7. A patch according to any of claims 4 to 6, when dependent upon claim 2, wherein the skin-coupling adhesive is located on the inner surface of the dielectric cover and extends around the support structure.

8. A patch according to claim 7, wherein the skin-coupling adhesive extends circumferentially around the support structure.

9. A patch according to any of the preceding claims, wherein at least a part of the dielectric cover is formed of an elastic material that can conform to the shape of the dielectric barrier discharge terminal when the terminal is brought into contact with the outer surface of the dielectric cover.

10. A patch according to any of the preceding claims, wherein the sealing mechanism comprises an outer adhesive layer on the outer surface of the dielectric cover.

11. A patch according to any of the preceding claims, wherein the dielectric cover has a thickness of at least 20 microns and no more than 2000 microns.

12. A patch according to any of the preceding claims, further comprising: an electrode on the outer surface of the dielectric cover; and, an electrical connector electrically coupled to the electrode for electrically coupling the electrode to a plasma generating device that includes the dielectric barrier discharge terminal.

13. A plasma generating device for use with a patch according to any of the preceding claims, the plasma generating device comprising:a high voltage power supply;a dielectric barrier discharge terminal comprising an electrode electrically coupled to the high voltage power supply;a controller operable to control the high voltage power supply; and,a contact sensor electrically coupled to the controller and configured to detect whether the dielectric barrier discharge terminal is in contact with the patch,wherein the controller is configured to prevent the high voltage power supply from supplying power to the electrode when the contact sensor detects that the dielectric barrier discharge terminal is not in contact with the patch.

14. A plasma generating device according to claim 13, wherein the contact sensor comprises a conductive sensor.

15. A plasma generating device according to claim 13 or claim 14,wherein the plasma generating device comprises a plurality of contact sensors electrically coupled to the controller; and,wherein the controller is configured to prevent the high voltage power supply from supplying power to the electrode when one or more of the contact sensors detects that the dielectric barrier discharge terminal is not in contact with the patch.

16. A plasma generating device according to any of claims 13 to 15, wherein the dielectric barrier discharge terminal comprises a plurality of electrodes electrically coupled to the high voltage power supply.

17. A system for administering plasma to a user’s skin, the system comprising:a patch for applying to a user’s skin; and,a plasma generating device,wherein the plasma generating device comprises:a high voltage power supply;a dielectric barrier discharge terminal comprising an electrode electrically coupled to the high voltage power supply; and, wherein the patch comprises:a dielectric cover having an inner surface and an outer surface; and,a support mechanism for supporting the dielectric cover to define an air cavity between the inner surface of the dielectric cover and the user’s skin when the patch is applied to the user’s skin,wherein the dielectric cover comprises a sealing mechanism for forming an air-tight contact between the outer surface of the dielectric cover and the dielectricbarrier discharge terminal of the plasma generating device for generation of plasma within the air cavity.

18. A system according to claim 17, wherein the patch further comprises a skin-coupling 5 adhesive for sealing the air cavity by creating an air-tight seal between the dielectric cover and the user’s skin when the patch is applied to the user’s skin.

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