Transducer array for tumor treatment field (TT field) therapy using a dedicated flexible circuit to implement temperature sensing.

Abstract

An alternating current field (e.g., a tumor treatment field or TT field) can be applied to a subject's body using an apparatus (e.g., a transducer array) that includes a first PCB having metal pads for coupling an AC signal to the subject's body with a high current, and a second, less expensive PCB capable of handling only lower currents. The first PCB is located in the central part of the apparatus, and the second PCB is located in the peripheral part of the apparatus. A temperature sensor (e.g., a thermistor) is electrically connected to the second PCB. In some embodiments, the second PCB is significantly larger than the first PCB.

Description

[Background Art]

[0001] [Cross-Reference to Related Applications] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 541,419 filed on September 29, 2023, the entire contents of which are incorporated herein by reference.

[0002] Tumor Treatment Field (TTField) therapy is a proven approach for treating tumors using alternating electric fields at a frequency of, for example, 50 kHz to 1 MHz, more commonly 100 kHz to 500 kHz. Conventionally, the alternating electric field is induced by electrode assemblies (for example, arrays of capacitively coupled electrodes, also referred to as transducer arrays) placed on the subject's skin on opposite sides of the subject's body. When an AC voltage is applied between the opposing electrode assemblies, an AC current flows through the electrode assemblies into the subject's body. Further, higher current is more strongly correlated with higher therapeutic effect.

[0003] Alternating electric fields can also be used to treat medical conditions other than tumors. For example, as described in Patent Document 1, an alternating electric field of, for example, 75 kHz to 150 kHz can be used to increase the permeability of the blood-brain barrier (BBB), so that, for example, chemotherapeutic agents can reach the brain.

[0004] An example of a prior art electrode assembly that can be used to apply an alternating electric field to a subject's body is the electrode assembly described in Patent Document 2. These electrode assemblies include nine electrode elements, each of which includes (a) a metal layer and (b) a ceramic layer with a very high dielectric constant positioned between the metal layer and the subject's skin. A thermistor positioned in a small central hole of most of the electrode elements is included to perform temperature measurements at those electrode elements.

[0005] Another example of a prior art electrode assembly that can be used to apply an alternating electric field to a subject's body is the electrode assembly described in Patent Document 3. These electrode assemblies have a flexible circuit, which includes a plurality of conductive pads on the front side of the flexible circuit, and a plurality of flexible polymers disposed on and in front of the conductive pads. A plurality of thermistors positioned behind the flexible circuit in thermal contact with each conductive pad are used to detect the temperature of the conductive pads.

[0006] To use any of these prior art electrode assemblies, an AC voltage is applied to the metal layer of the electrode elements in the opposing electrode assembly, generating a TT field on the subject's body. The skin beneath the electrode elements warms up during use, resulting in a set of hotter spots directly beneath the electrode elements and a set of cooler areas directly beneath the space between the electrode elements. These hot spots limit the amount of current that can be delivered through the prior art electrode assembly, as the duty of care requires that the skin temperature remain below a safety threshold (e.g., 41°C). More specifically, the prior art system relies on a signal from a thermistor to ensure that the current is low enough to prevent the subject's skin temperature from exceeding the safety threshold. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 10,967,167 [Patent Document 2] U.S. Patent No. 8,715,203 [Patent Document 3] U.S. Patent Publication No. 2021 / 0402179 [Overview of the project]

[0008] One aspect of the present invention relates to a first device for applying an electrical signal to the body of a subject. The first device comprises a first PCB, a second PCB, and a plurality of temperature sensors. The first PCB has a first substrate and at least one metal pad disposed on the skin-facing front surface of the first substrate. The second PCB has a second substrate and a plurality of conductive traces, and the second PCB is flexible. Each of the plurality of temperature sensors is electrically connected to at least one of the conductive traces of the second PCB. The first PCB has an outer boundary, and the first and second PCBs are positioned such that, when viewed from a direction perpendicular to the first PCB, the second PCB is outside the outer boundary of the first PCB.

[0009] Some embodiments of the first apparatus further include a flexible backing positioned on the back of the first and second PCBs. The flexible backing is configured to support the first and second PCBs, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends laterally across both the first and second PCBs and adheres to the skin. The first PCB is flexible, and multiple conductive traces on the second PCB are formed using conductive ink. Optionally, in these embodiments, the first PCB has a first area, and the second PCB has a second area, where the second area is larger than the first area.

[0010] Some embodiments of the first apparatus further include a flexible backing positioned on the back of the first and second PCBs. The flexible backing is configured to support the first and second PCBs, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends laterally across both the first and second PCBs and adheres to the skin. The first PCB is flexible, and multiple conductive traces on the second PCB are formed using conductive ink. These embodiments also further include a first conductive adhesive or conductive gel layer disposed on and in front of both the first and second PCBs, an anisotropic material layer disposed on and in front of the first conductive adhesive or conductive gel layer, and a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

[0011] Optionally, in the embodiments described in the above paragraph, the anisotropic material layer comprises graphite. Optionally, in the embodiments described in the above paragraph, the anisotropic material layer comprises a layer of pyrolysis graphite, graphitized polymer film, or graphite foil made from compressed high-purity exfoliated mineral graphite. Optionally, the embodiments described in the above paragraph may further comprise at least one dielectric material layer disposed in front of at least one metal pad (optionally disposed on and in front of at least one metal pad), wherein the at least one dielectric material layer has a dielectric constant of at least 10. Optionally, in the embodiments described in the above paragraph, the first PCB further comprises at least one dielectric material layer disposed on and in front of at least one metal pad, wherein the at least one dielectric material layer has a dielectric constant of at least 10. Optionally, each of the metal pads in the latter embodiment may be copper.

[0012] Some embodiments of the first apparatus further include a connector fixed to a second PCB. Multiple temperature sensors, multiple conductive traces on the second PCB, and the connector are positioned and arranged so that temperature readings obtained using the multiple temperature sensors can be accessed via the connector.

[0013] In some embodiments of the first apparatus, the first PCB has a first area, and the second PCB has a second area, the second area being at least twice the area of ​​the first PCB.

[0014] In some embodiments of the first apparatus, the first and second substrates partially or completely overlap each other within an overlapping region and are stacked together within the overlapping region. In some embodiments of the first apparatus, the first and second substrates are the same substrate, or the first and second substrates are on the same plane.

[0015] In some embodiments of the first apparatus, the multiple temperature sensors include at least two temperature sensors, or at least three temperature sensors, or at least four temperature sensors.

[0016] Another aspect of the present invention relates to a second device for applying electrical signals to the body of a subject. The second device comprises a flexible PCB, at least two temperature sensors, a first conductive adhesive or conductive gel layer, and a flexible backing. The flexible PCB has a central section and a peripheral section located outside the outer boundary of the central section, and the PCB has at least one metal pad disposed on the skin-facing front surface of the central section of the PCB, and a plurality of conductive traces. Each of the at least two temperature sensors is mounted on the peripheral section of the PCB and electrically connected to at least one of the conductive traces. The first conductive adhesive or conductive gel layer is disposed on and in front of the PCB. The flexible backing is positioned on the back side of the PCB. The flexible backing is configured to support the PCB, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends laterally across the PCB and adheres to the skin. In some embodiments, the second device comprises at least three temperature sensors, or at least four temperature sensors.

[0017] In some embodiments of the second apparatus, the central section of the flexible PCB is bounded by a convex hull that surrounds the outermost metal pad of at least one metal pad.

[0018] Some embodiments of the second apparatus further include an anisotropic material layer disposed on and in front of a first conductive adhesive or conductive gel layer, wherein the anisotropic material layer has an area at least twice the area of ​​the central section, and a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

[0019] Optionally, in the embodiments described in the above paragraph, the anisotropic material layer comprises graphite. Optionally, in the embodiments described in the above paragraph, the anisotropic material layer comprises a layer of pyrolysis graphite, graphitized polymer film, or graphite foil made from compressed high-purity exfoliated mineral graphite.

[0020] Some embodiments of the second apparatus further include at least one dielectric material layer disposed in front of at least one metal pad. The at least one dielectric material layer has a dielectric constant of at least 10.

[0021] In some embodiments of the second apparatus, the PCB further comprises at least one dielectric material layer disposed on and in front of at least one metal pad, wherein the at least one dielectric material layer has a dielectric constant of at least 10. In some embodiments of the second apparatus, each conductive trace in the peripheral section connected to at least two temperature sensors of a plurality of conductive traces is formed using conductive ink. In some embodiments of the second apparatus, each of the metal pads is a copper pad. In some embodiments of the second apparatus, none of the metal pads are located in the peripheral section of the PCB.

[0022] Another aspect of the present invention relates to a third device for applying electrical signals to the body of a subject. The third device comprises a first PCB, a second PCB, a plurality of temperature sensors, and a flexible backing. The first PCB has a first substrate and at least one metal pad disposed on the skin-facing front surface of the first substrate. The second PCB has a second substrate and a plurality of conductive traces formed using conductive ink, and the second PCB is flexible. Each of the plurality of temperature sensors is electrically connected to at least one of the conductive traces of the second PCB. The flexible backing is positioned on the back of the first and second PCBs and is configured to support the first and second PCBs, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends laterally across both the first and second PCBs and adheres to the skin. The first PCB has an outer boundary, the second PCB has an outer boundary, and the first and second PCBs are positioned such that the convex hull that most closely surrounds the outer boundary of the second PCB is outside the outer boundary of the first PCB.

[0023] Some embodiments of the third apparatus further include a first conductive adhesive or conductive gel layer disposed on and in front of both a first PCB and a second PCB, an anisotropic material layer disposed on and in front of the first conductive adhesive or conductive gel layer, and a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

[0024] Optionally, in the embodiments described in the above paragraphs, the anisotropic material layer comprises graphite. Optionally, in the embodiments described in the above paragraphs, the anisotropic material layer comprises a layer of pyrolytic graphite made from compressed high-purity exfoliated mineral graphite, graphitized polymer film, or graphite foil. Optionally, in the embodiments described in the above paragraphs, the first PCB further comprises at least one dielectric material layer disposed over the at least one metal pad and in front of the at least one metal pad, and the at least one dielectric material layer has a dielectric constant of at least 10. In some embodiments of the third device, the plurality of temperature sensors comprises at least 2 temperature sensors, or at least 3 temperature sensors, or at least 4 temperature sensors. Brief Description of the Drawings

[0025] [Figure 1] 1 is a plan view of an apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject. [Figure 2] 2 is a cross-sectional view of the apparatus of FIG. 1. [Figure 3] 3 illustrates an example of how to use the apparatus of FIG. 1 to apply an alternating electric field (e.g., a TT field) to the body of a subject. [Figure 4] 4 is a plan view of another apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject. [Figure 5] 5 is a cross-sectional view of the apparatus of FIG. 4. [Figure 6] 6 illustrates another apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject. [Figure 7] 7 is a cross-sectional view illustrating yet another apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject. [Figure 8] 8 illustrates an apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject, where two PCBs are stacked. [Figure 9] 9 illustrates another apparatus for applying an alternating electric field (e.g., a TT field) to the body of a subject, where two PCBs are stacked.

[0026] Various embodiments will be described in detail below with reference to the attached drawings, where similar reference numerals represent similar elements. [Modes for carrying out the invention]

[0027] In particular, in the two prior art designs described above, the hottest spot is always located directly beneath one of the electrode elements. Therefore, it is reasonable for these prior art systems to rely on temperature readings obtained at the electrode elements. However, according to other designs relating to transducer arrays, obtaining temperature measurements only at the locations of the electrode elements may be insufficient to ensure that no part of the transducer array overheats beyond a safety threshold. This can be particularly important in designs that use sheets of thermally conductive material to distribute heat uniformly within any given transducer array. An example of this type of transducer array is described in U.S. Patent Publication 2023 / 0043071, which is incorporated herein by reference in its entirety.

[0028] Figure 1 is a plan view of a device 100 (e.g., a transducer array) for applying an alternating electric field (e.g., a TT field) to a subject's body, and Figure 2 is a cross-sectional view of the same device 100. The device 100 includes at least one metal pad 12 positioned in the central part of the device, and a set of temperature sensors (e.g., thermistors) T1-T8 positioned in the peripheral part of the device are used to obtain temperature readings around the device.

[0029] Apparatus 100 uses a flexible PCB 10 having a central section 10C and peripheral sections (i.e., sections located outside the outer boundary of the central section 10C). It should be noted that, as used herein, the term "PCB" refers to a printed circuit board, and this term encompasses rigid PCBs (e.g., with copper traces on a rigid epoxy substrate), flexible circuits (e.g., with copper traces on a flexible polyimide substrate), and printed circuits made by printing conductive ink on a flexible substrate.

[0030] PCB 10 has at least one metal pad 12 positioned in front of the central section 10C of the PCB, and a plurality of conductive traces (not shown). At least two temperature sensors T1-T8 (e.g., thermistors) are mounted on the peripheral section of PCB 10 (e.g., four or more temperature sensors for electrode elements / metal pads distributed in a square or rectangular pattern), and these temperature sensors are electrically connected to at least one of the conductive traces. Optionally, one or more additional temperature sensors (e.g., thermistors) T9 may be positioned in the central part of the device 100. A connector 15 is mounted on PCB 10 and is used to provide an electrical interface with the thermistors T1-T9 and at least one metal pad 12. If two or more metal pads 12 are included (as shown in Figures 1 and 2), all metal pads 12 can be connected by conductive traces (e.g., metal traces) 13, in which case only a single pin of the connector 15 is required to apply an AC signal to all of the metal pads 12. In an alternative embodiment (not shown), the conductive trace 13 can be omitted, and each metal pad 12 can be electrically connected to its own individual pin on the connector 15.

[0031] In the embodiments illustrated in Figures 1 and 2, the PCB 10 also includes a dielectric material layer 18 disposed on and in front of the metal pad 12, the dielectric material layer 18 (labeled "hi-K" in Figure 2) having a dielectric constant of at least 10. In some preferred embodiments, the dielectric material layer 18 has a dielectric constant of at least 20 or at least 40. A first conductive adhesive layer 50 may be disposed in front of the PCB 10. In Figures 1 and 2, the first conductive adhesive layer 50 is shown disposed on and in front of the PCB 10, with the rear surface of the conductive adhesive 50 adhering to the front surface of the dielectric material 18 and also to the front surface of the thermistors T1-T8 (and T9, if present). Note that in some embodiments, the dielectric material layer 18 is not included, in which case the rear surface of the first conductive adhesive layer 50 adheres to the front surface of the metal pad 12 and also to the front surface of thermistors T1-T8 (and T9, if present). It should be noted that in an alternative embodiment, a layer of conductive gel (e.g., hydrogel) can be used instead of the first conductive adhesive layer 50 shown in Figure 2.

[0032] A flexible lining 80 (e.g., a bandage-like lining) is positioned on the back side of the PCB 10, and this flexible lining 80 is configured to support the PCB. At least a portion of the flexible lining 80 extends laterally across the PCB, and the front of this portion is covered with a biocompatible adhesive that adheres to the skin. This portion of the flexible lining 80 helps to hold the device 100 against the subject's skin.

[0033] Embodiments illustrated in Figures 1 and 2 also include an anisotropic material layer (e.g., a sheet of graphite) 55 disposed on and in front of the first conductive adhesive layer 50, and a second conductive adhesive layer 60 disposed on and in front of the anisotropic material layer 55. The anisotropic material layer 55 may be a layer of pyrolysis graphite, a graphitized polymer film, or a graphite foil made from compressed high-purity exfoliated mineral graphite. The anisotropic material layer 55 has an area larger than (e.g., at least twice as large) the area of ​​the central section 10C. The anisotropic material layer 55 is preferably both thermally and electrically conductive and acts to spread both current and heat in all four directions (i.e., right, left, in-page in Figure 2, and out-of-page in Figure 2, which corresponds to right, left, up, and down in Figure 1). The second conductive adhesive layer 60 should be biocompatible and its function is to hold the device 100 to the body of the subject. It should be noted that in an alternative embodiment, a layer of conductive gel (e.g., hydrogel) can be used instead of the second conductive adhesive layer 60 shown in Figure 2.

[0034] In an alternative embodiment, the anisotropic material layer 55 and the second conductive adhesive layer 60 may be omitted, in which case the first conductive adhesive layer 50 should be biocompatible so that it can be directly adhered to the subject's skin.

[0035] Positioning temperature sensors T1-T8 in the peripheral sections of the device 100 is particularly advantageous in embodiments including an anisotropic material layer 55, as it allows for more uniform distribution of current and heat over a much larger surface area, unlike in embodiments of the prior art where the hottest spot is almost certainly directly beneath the electrode elements. As a result, additional factors, including, but not limited to, geometric and anatomical factors, may influence which parts of the device 100 become the hottest. In one example, geometric shape influences this because parts of opposing transducer arrays that are closest to each other tend to be hotter than parts of opposing transducer arrays that are farther apart. In another example, anatomical structure influences this because sections of the device 100 over parts of the subject's skin with lower blood flow tend to be hotter than sections over parts of the subject's skin with higher blood flow (because blood flow carries heat away from the device 100). Optionally, one or more additional temperature sensors T9 can be positioned in the central section 10C of the device 100.

[0036] Figure 3 illustrates an example of how the apparatus 100 shown in Figures 1 and 2 is used to apply an alternating current electric field (e.g., a TT field) to a target area within a subject's body. Referring to Figures 1-3, the first apparatus 100 is attached to the subject's skin on one side of the target area, and the second apparatus 100 is attached to the subject's skin on the opposite side of the target area. To apply an alternating current electric field within the target area, an AC voltage generator 120 applies an AC voltage (e.g., 50 kHz to 5 MHz, or 75 kHz to 300 kHz) between the metal pads 12 of the first apparatus 100 (Figures 1 and 2) and the metal pads 12 in the second apparatus 100. The AC signal from the AC voltage generator reaches each of the first and second apparatuses 100 via a set of cables terminated at connectors 15 on each apparatus 100. From the connectors 15, the signal is also sent to the respective metal pads 12 via their respective conductive traces (e.g., conductive metal traces, not shown) on the PCB 10.

[0037] The controller 130 checks the temperature of each of the temperature sensors T1 to T8 (and T9, if present) in each of the first and second devices 100 by inputting the respective signals from those temperature sensors. These signals reach the controller 130 via their respective conductive traces on each PCB 10, their respective connectors 15, and their respective cables. If the controller 130 determines that all temperature sensors are below the threshold temperature, the controller 130 can increase the voltage of the AC signal, which will consequently increase the current flowing through the first and second devices 100, which will consequently increase the strength of the AC electric field in the target region. On the other hand, if the controller 130 determines that any of the temperature sensors are at or approaching the threshold temperature, the controller 130 decreases the voltage of the AC signal, which will decrease the current, consequently lowering the temperature in the hottest region of the device 100.

[0038] In particular, the signals that the AC voltage generator 120 sends to the metal pads 12 of the first and second devices 100 have a relatively high current (e.g., about 1A or even higher). On the other hand, the signals that the controller 130 uses to check the temperature of each of the temperature sensors T1-T8 (and T9, if present) are orders of magnitude smaller (e.g., about 1mA or even lower). As a result, the PCB 10 can be implemented using relatively thick metal traces (e.g., copper traces) to send signals from the connector 15 to the metal pads 12, and relatively thin metal traces (e.g., copper traces) to send signals from the connector 15 to the temperature sensors T1-T8 (and T9, if present). While this is not a problem from a technical standpoint, it is suboptimal from an economic standpoint.

[0039] More specifically, because transducer arrays occupy a relatively large area (approximately 10 to 50 square inches), a single PCB 10 becomes relatively expensive if it is used for both transmitting signals (for applying the TT field) to the metal pads 12 and transmitting signals from temperature sensors T1 to T8 (and T9, if present). This is because, when a single PCB 10 is used, the entire PCB must be designed to accommodate the highest expected current, even if in reality only a relatively small portion of the PCB is used to carry the higher current. And a large PCB capable of accommodating a current of approximately 1A is relatively expensive. Embodiments described below in relation to Figures 4 to 7 address this economic problem.

[0040] Figure 4 is a plan view of another apparatus 200 (e.g., a transducer array) for applying an alternating electric field (e.g., a TT field) to a subject's body, and Figure 5 is a cross-sectional view of the same apparatus 200. The apparatus 200 includes a first PCB 30 positioned in the central part of the apparatus and a second PCB 40 positioned in the peripheral part of the apparatus. The first PCB 30 has an outer boundary (indicated as a -.- line), and the first and second PCBs are positioned such that the second PCB 40 is outside the outer boundary of the first PCB 30.

[0041] The central portion of the first PCB 30 comprises a first substrate and at least one metal pad 12 disposed on the front surface of the first substrate. If two or more metal pads 12 are included (as shown in Figures 4 and 5), all metal pads 12 can be connected by conductive traces (e.g., metal traces) 13. Conductive metal traces (e.g., copper traces, not shown) on the first PCB 30 are used to transmit signals from an AC voltage generator to the metal pads 12. Connectors (not shown) may be included on the first PCB 30 to input these signals, or the signals can be electrically connected directly to one of the metal pads 12 or metal traces 13 using actual wiring.

[0042] A second PCB 40 located in the peripheral portion of the apparatus 200 (having an outer boundary 40A and an inner boundary 40B, each shown as a dotted line in Figure 4) is flexible and has a second substrate having a plurality of conductive traces disposed on top. At least two temperature sensors T1-T8 (e.g., thermistors) are mounted on the second PCB 40, and these temperature sensors are electrically connected to at least one of the conductive traces. Optionally, one or more additional temperature sensors T9 (e.g., thermistors) may be positioned in the central portion of the apparatus 200 (e.g., on the second PCB 40, as shown in Figure 4). A connector 45 is mounted on the second PCB 40 and is used to provide an electrical interface with the thermistors T1-T9.

[0043] In the embodiments illustrated in Figures 4 and 5, the first PCB 30 also includes a dielectric material layer 18 disposed on and in front of the metal pad 12, the dielectric material layer 18 (labeled "hi-K" in Figure 5) having a dielectric constant of at least 10. In some preferred embodiments, the dielectric material layer 18 has a dielectric constant of at least 20 or at least 40.

[0044] The first conductive adhesive layer 50 is disposed on and in front of both the first PCB 30 and the second PCB 40, with the rear surface of the conductive adhesive 50 adhering to the front surface of the dielectric material 18 (of the first PCB 30). In some embodiments, the dielectric material layer 18 is not included (for example, as described below in relation to Figure 7). Note that in alternative embodiments, a layer of conductive gel (e.g., hydrogel) can be used instead of the first conductive adhesive layer 50 illustrated in Figure 5.

[0045] A flexible backing material 80 (e.g., a bandage-like backing material) is positioned on the back of both the first PCB 30 and the second PCB 40, and this flexible backing material 80 is configured to support both of those PCBs. At least a portion of the flexible backing material 80 extends laterally beyond the first PCB 30 and the second PCB 40, and the front of this portion is covered with a biocompatible adhesive that adheres to the skin. This portion of the flexible backing material 80 helps to hold the device 200 against the subject's skin. The boundaries of the flexible backing material 80 and the first PCB 30 and the second PCB 40 are schematically shown herein as squares or rectangles for simplification, but they can, of course, be any shape including circles, ovals, rounded triangles, etc.

[0046] Embodiments illustrated in Figures 4 and 5 also include an anisotropic material layer (e.g., a sheet of graphite) 55 disposed on and in front of the first conductive adhesive layer 50, and a second conductive adhesive layer 60 disposed on and in front of the anisotropic material layer 55. The anisotropic material layer 55 has an area larger than (e.g., at least twice as large) the area of ​​the first PCB 30. The anisotropic material layer 55 is preferably both thermally and electrically conductive and acts to spread both current and heat in all four directions, as described above in relation to Figures 1 and 2. The second conductive adhesive layer 60 should be biocompatible and its function is to hold the device 200 to the subject's body. Note that in alternative embodiments, a layer of conductive gel (e.g., a hydrogel) can be used instead of the second conductive adhesive layer 60 illustrated in Figure 5.

[0047] In an alternative embodiment, the anisotropic material layer 55 and the second conductive adhesive layer 60 may be omitted, in which case the first conductive adhesive layer 50 should be biocompatible so that it can be directly adhered to the subject's skin.

[0048] Positioning the temperature sensors T1 to T8 in the peripheral section of the device 200 is advantageous for the same reasons described above in relation to the embodiments shown in Figures 1 and 2.

[0049] In particular, unlike the embodiments of Figures 1 and 2, where low-current PCB traces (used to interface with temperature sensors T1-T9) are mounted on the same PCB as high-current traces (used to interface with metal pads 12), all traces on the second PCB 40 are low-current traces. This allows the second PCB 40 to be manufactured using very inexpensive technology (e.g., using conductive traces made from conductive ink instead of copper). Furthermore, since all high-current traces are located on the relatively small first PCB 30, the embodiments of Figures 4 and 5 can be implemented using a relatively small high-current PCB (using expensive copper technology) and a relatively large low-current PCB using inexpensive technology (e.g., conductive ink). And because the size of the expensive technology PCB 30 in the embodiments of Figures 4 and 5 is much smaller than the single large expensive technology PCB 10 in the embodiments of Figures 1 and 2, the former can achieve significant cost savings compared to the latter.

[0050] The apparatus 200 illustrated in Figures 4 and 5 is used in a manner similar to how apparatus 100 (illustrated in Figures 1 and 2) is used as described above in relation to Figure 3, with one obvious exception. More specifically, instead of using a single connector 15 to send signals to and from both thermistors T1-T8 (and T9, if present) and the metal pad 12 (as in the embodiments of Figures 1 and 2), the embodiments of Figures 4 and 5 use a connector 45 on a second PCB 40 solely to send signals to thermistors T1-T8 (and T9, optionally). Then, either an additional connector (not shown) or a real wiring connector is used to send the ACTT field signal to the metal pad 12.

[0051] Figure 6 illustrates another apparatus 200' which is similar to apparatus 200 described above in relation to Figures 4 and 5, except that there is a larger space between the outer boundary of the first PCB 30 (shown as a -.- line) and the inner boundary 40B of the second PCB 40 (shown as a dotted line). The use of this apparatus 200' (and the labeling of the components of 200' in Figure 6) is the same as the use of apparatus 200 described above (and the labeling of the components of 200 in Figures 4 and 5).

[0052] Figure 7 illustrates yet another apparatus 200'' which is similar to the apparatus 200 described above in relation to Figures 4 and 5, except that the dielectric material layer 18 is omitted. (As a result, the rear surface of the first conductive adhesive layer 50 will be bonded to the front surface of the metal pad 12 of the first PCB 30). This apparatus 200'' is used instead of the apparatus 200 described above in situations where it is desirable to conductively couple an AC signal from an AC voltage generator 120 (shown in Figure 3) to the subject's body (as opposed to capacitively coupling that signal to the subject's body).

[0053] In the embodiments described above in relation to Figures 4 and 6, a space exists between the outer boundary of the first PCB 30 (shown as -.- lines) and the inner boundary 40B of the second PCB 40 (shown as a dotted line). This space is small in Figure 4 and large in Figure 6, and there is no portion of either Figure 4 or Figure 6 showing the second PCB 40 overlapping the first PCB 30. However, in alternative embodiments, the second PCB 40 can partially or completely overlap the first PCB 30. Figure 8 is an example of such an embodiment 300. This embodiment in Figure 8 is similar to embodiment 200 in Figure 4, except that the second PCB 40 (shown with diagonal cross-hatching) is a rectangle with no cutout area. Preferably, in an arrangement where the first PCB 30 and the second PCB 40 overlap, the second PCB 40 is positioned behind the first PCB 30 (i.e., the first PCB 30 is in front and the second PCB 40 is behind). In this example, the first PCB 30 has an outer boundary (shown as a -.- line), and the second PCB 40 has an outer boundary 40A (shown as a dotted line). The first PCB 30 and the second PCB 40 are positioned such that the outer boundary of the second PCB 40 lies with the outer boundary of the first PCB 30 (when viewed from a direction perpendicular to the first PCB 30). In Figure 8, the second PCB 40 completely overlaps the first PCB 30. In optional embodiments where the second PCB 40 partially or completely overlaps the first PCB 30, the first PCB 30 and the second PCB 40 can be laminated together. Optionally, the lamination may include a conductive adhesive between the first PCB 30 and the second PCB 40.

[0054] Figure 9 shows a modification of the embodiment of Figure 8, in which the second PCB 40 has an irregular shape. In this configuration, the first PCB 30 has an outer boundary (shown as a -.- line), and the second PCB 40 has an outer boundary 40A (shown as a dotted line), and the first PCB 30 and the second PCB 40 are positioned such that the rectangle that most closely surrounds the outer boundary of the second PCB 40 lies on the outer boundary of the first PCB 30 (even if a portion of the first PCB 30 is actually outside the outer boundary of the second PCB 40).

[0055] Headings are provided for convenience only and should not be construed as limiting the invention in any way. Embodiments illustrated under any heading or portion of this disclosure may be combined with embodiments illustrated under the same or any other heading or portion of this disclosure. Unless otherwise stated herein or unless explicitly stated otherwise by context, all combinations of the elements described herein in all possible modifications thereof are encompassed by this disclosure. For example, an embodiment described in dependent claims form with respect to a given embodiment (e.g., a given embodiment described in independent claims form) may be combined with other embodiments (described in independent or dependent claims form).

[0056] While the present invention has been disclosed with reference to certain embodiments, many modifications, alterations, and changes are possible to the described embodiments without departing from the art and scope of the invention, as defined in the appended claims. Therefore, the present invention is not limited to the described embodiments and is intended to encompass the entire scope defined by the following claims and their equivalents.

Claims

1. A device for applying electrical signals to a subject's body, wherein the device is A first PCB having a first substrate and at least one metal pad disposed on the front surface of the first substrate facing the skin, A second PCB having a second substrate and a plurality of conductive traces, wherein the second PCB is flexible, The invention comprises a plurality of temperature sensors, each of which is electrically connected to at least one of the conductive traces of the second PCB, An apparatus in which the first PCB has an outer boundary, and the first and second PCBs are positioned such that, when viewed from a direction perpendicular to the first PCB, the second PCB is outside the outer boundary of the first PCB.

2. The invention further comprises a flexible backing positioned on the back side of the first PCB and the second PCB, wherein the flexible backing is configured to support the first PCB and the second PCB, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends laterally beyond both the first PCB and the second PCB and adheres to the skin. The first PCB is flexible, The apparatus according to claim 1, wherein the plurality of conductive traces of the second PCB are formed using conductive ink.

3. The apparatus according to claim 2, wherein the first PCB has a first area, and the second PCB has a second area, the second area being larger than the first area.

4. A first conductive adhesive or conductive gel layer disposed on and in front of both the first PCB and the second PCB, An anisotropic material layer disposed on and before the first conductive adhesive or conductive gel layer, The apparatus according to claim 2, further comprising a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

5. The apparatus according to claim 4, wherein the anisotropic material layer includes graphite.

6. The apparatus according to claim 4, wherein the anisotropic material layer includes a layer of pyrolysis graphite, a graphitized polymer film, or a graphite foil made from compressed high-purity exfoliated mineral graphite.

7. The apparatus according to claim 1, wherein each of the metal pads is a copper pad.

8. The apparatus according to claim 1, further comprising at least one dielectric material layer disposed in front of the at least one metal pad, or optionally disposed on and in front of the at least one metal pad, wherein the at least one dielectric material layer has a dielectric constant of at least 10.

9. The apparatus according to claim 1, further comprising a connector fixed to the second PCB, wherein the plurality of temperature sensors, the plurality of conductive traces of the second PCB, and the connector are positioned and arranged so that temperature readings obtained using the plurality of temperature sensors can be accessed via the connector.

10. The apparatus according to claim 1, wherein the first and second substrates partially or completely overlap each other within an overlapping region and are stacked together within the overlapping region.

11. The apparatus according to claim 1, wherein the first and second substrates are the same substrate, or the first and second substrates are on the same plane.

12. A device for applying electrical signals to a subject's body, wherein the device is A flexible PCB having a central section and a peripheral section located outside the outer boundary of the central section, wherein the PCB has at least one metal pad disposed on the skin-facing front surface of the central section of the PCB, and a plurality of conductive traces, At least two temperature sensors, each of which is mounted on the peripheral section of the PCB and electrically connected to at least one of the conductive traces, A first conductive adhesive or conductive gel layer disposed on and in front of the PCB, A device comprising: a flexible backing positioned on the back side of the PCB, wherein the flexible backing is configured to support the PCB, and at least a portion of the flexible backing is covered with a biocompatible adhesive that extends beyond the PCB in the lateral direction and adheres to the skin.

13. The apparatus according to claim 12, wherein the central section of the flexible PCB is bounded by a convex hull surrounding the outermost metal pad of at least one of the metal pads.

14. An anisotropic material layer disposed on and in front of the first conductive adhesive or conductive gel layer, wherein the anisotropic material layer has an area at least twice the area of ​​the central section, The apparatus according to claim 12, further comprising a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

15. The apparatus according to claim 14, wherein the anisotropic material layer includes graphite.

16. The apparatus according to claim 12, wherein the PCB further comprises at least one dielectric material layer disposed on and in front of the at least one metal pad, and the at least one dielectric material layer has a dielectric constant of at least 10.

17. The apparatus according to claim 12, wherein none of the at least one metal pads are located within the peripheral section of the PCB.

18. A device for applying electrical signals to a subject's body, wherein the device is A first PCB having a first substrate and at least one metal pad disposed on the front surface of the first substrate facing the skin, A second PCB having a second substrate and a plurality of conductive traces formed using conductive ink, wherein the second PCB is flexible, A plurality of temperature sensors, each of which is electrically connected to at least one of the conductive traces of the second PCB, A flexible backing material positioned on the back side of the first PCB and the second PCB, wherein the flexible backing material is configured to support the first PCB and the second PCB, and at least a portion of the flexible backing material is covered with a biocompatible adhesive that extends laterally beyond both the first PCB and the second PCB and adheres to the skin, comprising: An apparatus in which the first PCB has an outer boundary, the second PCB has an outer boundary, and the first and second PCBs are positioned such that the convex hull that most closely surrounds the outer boundary of the second PCB is outside the outer boundary of the first PCB.

19. A first conductive adhesive or conductive gel layer disposed on and in front of both the first PCB and the second PCB, An anisotropic material layer disposed on and before the first conductive adhesive or conductive gel layer, The apparatus according to claim 18, further comprising a second conductive adhesive or conductive gel layer disposed on and in front of the anisotropic material layer.

20. The apparatus according to claim 19, wherein the anisotropic material layer includes graphite.

21. The apparatus according to claim 19, wherein the first PCB further comprises at least one dielectric material layer disposed on and in front of the at least one metal pad, the at least one dielectric material layer having a dielectric constant of at least 10.

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