A component for an electrochemical device

Abstract

A component 201 for an electrochemical device includes a Membrane Electrode Assembly (MEA) 113; a cathode plate 101; and an anode plate 102. The cathode plate includes a first insulating layer between

Description

The present disclosure relates to components for electrochemical devices, electrochemical devices, uses of electrochemical devices and methods of manufacture of a component for an electrochemical device. BACKGROUND An example of electrochemical device is a solid-polymer-electrolyte fuel cell. A fuel cell is an electrochemical device which generates electrical energy and heat from a reactant or oxidant (e.g. pure oxygen or air) and a fuel (e.g. hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative). Fuel cell technology finds application in stationary and mobile applications, such as power stations, vehicles and laptop computers. Typically, a fuel cell comprises two electrodes, an anode and a cathode, separated by an electrolyte membrane that allows ions (e.g. hydrogen ions), but not free electrons, to pass through from one electrode to the other. A catalyst on the electrodes accelerates a reaction with the fuel on the anode to separate electrons and protons / cations, and oxidant on the cathode to undergo a reduction reaction to water. A circuit can then be formed between anode and cathode to generate a current to power a load. A reactant fluid, e.g. oxygen or reactant air, is supplied to the cathode and a fuel, e.g. hydrogen, is supplied to the anodes. A single pair of electrodes separated by an electrolyte membrane is called a membrane electrode assembly (MEA). The MEA can also refer to a combination of electrolyte, electrodes and gas diffusion layers on top of the electrode. A fuel cell MEA operating under a moderate load produces an output voltage of about 0.7V, which is often too low for many practical considerations. In order to increase this voltage, MEAs are typically assembled into a stack as shown in FIG. 1. Each MEA 1 has a layer of electrolyte membrane la (such as a Nation™ membrane), which comprises an ion-permeable membrane sandwiched between two electrode layers, and an anode 2 and a cathode 3 on either side of the electrolyte membrane. Adjacent MEAs can be separated by an electrically conducting bipolar separator plate 4, and a fuel (e.g. hydrogen) 6 and an oxidant 5 (e.g. oxygen gas or'reactant air') flow through the channels provided on opposing sides of the bipolar plate. End plates 9 are connected to an external circuit via an electrical connector 7, 8. The number of these MEAs in a stack in a fuel cell determines the total voltage, and the surface area of each membrane electrode determines the total current. Catalyst layers adjacent to the electrodes increase the rate of and efficiency of the reactions at the electrodes. FIG. 2 shows an exemplary fuel cell of the prior art (see e.g. WO 2012 / 117035) in which a plurality of fuel cell boards 22 are stacked between two endplates 21 in order to provide increased voltage and power. Electrode pairs are arranged in a series along either side of a single layer of polymer electrolyte 10, such as a Nation™ membrane. Anodes 11 are disposed on one surface of these membranes and cathodes 12, separated by gaps are disposed on the other, opposite, surface of these membranes. The anode and cathode respectively of two adjacent electrode pairs may partially overlap. Through-membrane electrical connectors 13 connect the electrodes across the membrane in the overlapping region, and may be produced by a homogeneous chemical deposition process. A catalyst layer adjacent to the electrodes encourages the reactions at the electrodes. A fuel 17, such as hydrogen gas, flows along the face of the fuel cell board 22 supplying the anodes 11 and a reactant or oxidant 16, such as oxygen gas or air, flows along the surface of the fuel cell board 22 supplying the cathodes 12. One electrode at the edge of the upper surface and one electrode at another edge of the lower surface of the fuel cell board are connected to an external circuit via an electrical connection 18, 19. In this series arrangement, the surface area of an electrode pair determines the size of the current for a fuel cell board 22, but the voltage accumulates in proportion to the number of electrode pairs on that fuel cell board 22. The end cathodes and anodes 11 on each fuel cell board may be connected to respective first and second output lines via electrical connections 18, 19. The connection between each fuel cell board in the stack and the second output line can be controlled by a switch mechanism such as a field-effect transistor (FET) switch providing power handling and control directly at the cell. Each of these switches can be controlled by individual control lines. There are a number of factors that determine the performance of a fuel cell. Fuel cells can have different type of electrolyte membranes, for example proton exchange membranes PEM could be engineered for low temperature operation (LT PEM) or for high temperature operation (HT PEM). When considering fuel cell using a LT PEM, maintaining the correct water content in the electrolyte membrane is essential for optimising a fuel cell's performance. The membrane requires a certain level of moisture to operate and conduct the ionic current efficiently so that the fuel cell current does not drop. Water produced by the cell is removed by the flow of fluid along the cathode or wicked away. Conversely, when a fuel cell is equipped with a high temperature PEM, removal of water vapor and maintaining the correct operational temperature are important for stable performance and to avoid damage to the membrane. Other examples of fuel cell are known to the person skilled in the art. Overheating of a fuel cell stack can cause problems and cooling is often required. This is generally achieved via the supply of a heat exchange fluid to cool down the system, a coolant fluid (e.g. air or water) that circulates within the stack. In addition, a reactant fluid (e.g. oxygen or reactant air) is required by the cathodes to enable a reaction. Thus, fuel cell and fuel cell stack temperature management is important, and can be a limiting or defining factor in fuel cell performance. For example, fuel cells may be below the optimal operation temperature at start up, or for example fuel cells may rise above the optimal operation temperature during operation. Further, fuel cell temperature may be inconsistent throughout a fuel cell stack (temperature imbalances). Environmental factors may also play a part in the need to control the thermal properties of a fuel cell, for example different thermal management will be required in low temperature environments to high temperature environments. Being able to manage or control the thermal properties of a fuel cell, e.g. heating or cooling of a fuel cell, is an important part of fuel cell operation. Fuel cells may require quick system reactions to temperature changes and efficiency improvements through thermal management will help to improve the performance of fuel cells. Thermal control design must be balanced with the potentially limited space availability in fuel cells and the potential loss of efficiency and increased manufacture costs with complicated thermal control systems, e.g. cooling, systems. Fuel cell power and valuable space inside fuel cell boxes can be lost utilising heat pump or other such thermal management systems. It is often desirable to design fuel cells to be as compact or space efficient as possible, particularly in the stack of fuel cell boards within a fuel cell itself. Reducing the size of fuel cells and the size of the fuel cell stack particularly can be advantageous. Similar considerations are also important for other electrochemical devices, such as electrolysers. Heat management in an electrolyser is key to maintaining the performance and durability during operation. For efficient operation the cell / stack should maintain the optimum operating temperature for the membrane / catalyst (i.e. 60-80C), during start up stacks typically run at lower efficiencies as they heat up to the target materials. Additionally, during operation if the cell was to overheat this can result in damage of membrane and or catalyst materials shortening the lifetime In view of the foregoing, it is desirable to provide improved components for electrochemical devices and improved means to manage the thermal properties of electrochemical devices whilst being cost effective and not adversely affecting the efficiency, affordability or size of the electrochemical devices. SUMMARY An aspect of the invention provides an component for an electrochemical device. This comprises a Membrane Electrode Assembly (MEA), the MEA comprising at least one ion permeable membrane, at least one anode, and at least one cathode, wherein one or more of the anodes are arranged on a first surface of the ion permeable membrane and one or more of the cathodes are arranged on a second surface of the ion permeable membrane. The MEA is located between a cathode plate and an anode plate. The cathode plate comprises a first insulating layer between a first conductive layer and a second conductive layer. The cathode plate comprises a first fluid path. The first conductive layer comprises the first fluid path. The anode plate comprises a second insulating layer between a third conductive layer and a fourth conductive layer. The anode plate comprises a second fluid path. The third conductive layer comprises the second fluid path. The MEA is located between the first conductive layer of the cathode plate and the third conductive layer of the anode plate so that the first fluid path is arranged such that a fluid can flow to or from the one or more cathodes and so that the second fluid path is arranged such that a fluid can flow to or from to the one or more anodes. The first conductive layer on the first insulating layer and the second conductive layer on the second insulating layer are adjacent the anodes or cathodes, and the electrically conducting material can act to carry electrical current to or away from the anodes and / or the cathodes. Placement of fluid pathways within just the conductive layers allows for the use of a thinner insulating core compared to previous designs and obviates the need for cap layers on fuel cell boards or in the fuel cell stack, and an increased amount of conductive material, coupled with a thinner insulating core, allows for a great control of the thermal properties of the fuel cell boards and fuel cell stacks overall. Any conductive layer may just be a partial layer or multiple partial layers on an insulating layer, some of each of those parts of the conductive layer comprising the fluid paths described herein. These may be conductive material "lands". Areas between the conductive material (lands) may form the fluid paths described herein. Those paths may form only in the conductive material and only have a base or floor of insulating material, or may have a base or floor also of conductive material, they may be solely contained in one or more areas of conductive material on an insulating layer. This may apply to any conductive material described herein. Preferably, the first conductive layer comprises the first fluid path and the second conductive layer comprises a third fluid path for a heat exchange fluid. The third conductive layer may comprise the second fluid path and the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid. The first conductive layer may comprise the first fluid path, the second conductive layer may comprise a third fluid path for a heat exchange fluid, the third conductive layer may comprise the second fluid path and the fourth conductive layer may comprise a fourth fluid path for a heat exchange fluid. Preferably, the second conductive layer comprises a third fluid path for a heat exchange fluid and / or the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid. Heat exchange fluids may control the thermal properties or control the temperature of the component, preferably at least the thermal properties or the temperature of the at least one anode of a component. The heat exchange fluid is separated from any oxidant fluid, these are different fluid flows, even if both are air. Preferably, no part of the part of the first fluid path from which or to which fluid flows to or from the cathodes is in or through the first insulating layer, and / or no part of the part of the second fluid path from which or to which fluid flows to or from the anodes is in or through the second insulating layer. This may be no part of the flow field which supplies a reactant to the cathodes or the anodes. Preferably, no part of the third fluid path and / or the fourth through path is in or through first insulating layer or the second insulating layer. Preferably, the cathode plate is a PCB. Preferably, the anode plate is a PCB. Preferably the insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene or G-10. Preferably, the insulating layer comprises FR-4. Preferably the one or more PCBs comprise FR-4 layers, also known as FR-4 epoxy resin, polyimide and / or other polymeric materials. Preferably, there may be multiple layers of insulating material to form a single layer, e.g. multiple insulating layers. Preferably, at least one of or both of the cathode plate and the anode plate comprises one or more means to conduct electrical current and heat through the insulating layer, preferably wherein the means to conduct electrical current and heat through the insulating layer are plated through holes and / or conductive material filled through holes. Preferably the plated through holes are copper plated through holes and / or conductive resin filled holes. These form an electrical connection and thermal connection between the two conductive layers on one or both of the insulating layers. The electrically conducting layers may act to carry electrical current to or away from conductive through holes, e.g. conductive material plated through holes or conductive material filled through holes, which may be formed through the body of the insulating layer(s). The at least some electrically conducting material may also act to carry electrical current to or away from adjacent components or other components of the device. Preferably, the one or more means to conduct electrical current and heat through the insulating layer are located within one or more of the fluid paths located in the conductive layer of the anode plate and / or the cathode plate. The means to conduct electrical current and heat through the insulating layer may be located in floor or bottom of the fluid paths, in the conductive material floor or bottom of the fluid path. Preferably, the one or more means to conduct electrical current and heat through the insulating layer are located in the area between one or more of the fluid paths located in the conductive layer of the anode plate and / or the cathode plate. The means to conduct electrical current and heat through the insulating layer may be located in the lands between the fluid paths. Preferably, one or more of the conductive layers comprise metal. Preferably, the metal comprises copper and / or nickel. Preferably the conductive material is graphite. Preferably, the conductive layers comprise a further conductive coating, preferably on top of the conductive layer. Preferably, in the conductive layers facing the anode(s) and cathode(s) (first and third consecutive layers) none of the metal is exposed to the fluid in the fluid paths because of the further conductive coating. Preferably, none of the metal is exposed to the fluid in reactant fluid paths because of a further conductive coating. Preferably, the one or more fluid paths are formed by chemical etching into the conductive layer. Preferably, the one or more fluid paths are formed by chemical etching, electrochemical machining or any other method of removing material from conductive layer. A conductive coating can then be applied on top of the conductive material once the conductive layer has been etched. Electrochemical machining, chemical etching or any other method of removing material from a conductive layer allows the decoupling of the fluid path geometry on opposite sides of the same plate (cathode and / or anode plate), allowing for different fluid pathways on different faces of boards. These methods allow independent creation of flow paths on the same plate but different sides or different parts of a plate. The first fluid path may be independently created from the third fluid path. The second fluid path may be independently created from the fourth fluid path. Or any fluid path may be independently created from another fluid path on the same or another face / side of the same plate. Preferably, the first and / or the second conductive layers are thicker than the first insulating layer. Preferably, the third and / or the fourth conductive layers are thicker than the second insulating layer. Preferably, the first conductive layer has multiple first flow paths. Preferably, the second conductive layer has multiple third flow paths. Preferably, the third conductive layer has multiple second flow paths. Preferably, the fourth conductive layer has multiple fourth flow paths. Preferably, any one or more of the flow paths are serpentine or substantially linear, or substantially parallel to other flow paths in the same layer. Preferably, one or more of the flow paths comprise flow restrictions or flow directional changes to perturbate fluid flow at defined intervals and / or to increase mass flow velocity and / or a change in pressure drop. Preferably, one or more flow paths are convergent flow fields with tapered channels dimensions. These can introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemical device / board. Preferably, one or more of the flow paths have cascade-type fractal designs, where the flow is split down a number of levels before it reaches the electrodes. These can help maintaining a fixed pressure throughout the surface of the MEA and could promote a uniform fuel utilisation relative to more traditional designs. Preferably, the components may comprise at least one of the following: multiple first fluid paths which are substantially linear and substantially parallel with each other, multiple second fluid paths which are substantially linear and substantially parallel with each other and / or multiple third / fourth fluid paths which are substantially linear and substantially parallel with each other. Preferably, the flow path geometry of the first fluid paths is different to the flow path geometry of the second fluid paths. Preferably, the flow path geometry of the first fluid path is different to the flow path geometry of the third fluid path. Preferably, the flow path geometry of the second fluid path is different to the flow path geometry of the fourth fluid path. The flow path geometry of a fluid path on one face of the anode plate and / or the cathode plate may be different to the flow path geometry of fluid path on the opposing face of the same anode plate or cathode plate. The flow paths on opposing faces / opposite sides of the same plate may be independently created or decoupled from each other. Preferably, one or more of the fluid paths depths is shallower or smaller than the full depth or thickness of the conductive layer, so all three walls of the fluid path are of the conductive layer. Preferably, one or more of the fluid paths is not through the whole body of the conductive layer it is located within. Preferably, the or each component comprises a plurality of anodes and a plurality of cathodes, wherein the anodes and cathodes are arranged in pairs opposite each other across the ion permeable membrane. Preferably, in a single component all of the anodes are on the same side of the ion permeable membrane and all cathodes are on the other side of the same ion permeable membrane. Preferably, each component only comprises one anode and / or each component only comprises one cathode. Preferably, the Membrane Electrode Assembly (MEA) further comprises at least one gas diffusion layer. The one or more gas diffusion layer(s) may be between the at least one cathode or all of the cathodes and the first conductive layer and at least one or all of the first fluid path(s). The one or more gas diffusion layer(s) may be between the at least one anode or all of the anodes and the second conductive layer and at least one or all of the second fluid path(s). The MEA may comprise multiple gas diffusion layers as described herein. Preferably, the first fluid path is for an oxidant fluid, the second fluid path is for a reductant fluid. The reactant and heat exchange fluids may enter and leave the relevant fluid paths described herein via inlets and outlets. These inlets and outlets may connect the fluid paths to manifolds which supply the relevant fluids to the fluid paths. These manifolds are those described herein, but may be apertures in the insulating layers. Preferably, the heat exchange fluid comprises water or a mixture of water and glycol, preferably wherein the water is deionised water. Preferably this may also include benzotriazole. The water may or may not be deionised water, dependent on the application. Preferably the heat exchange fluid is fluid with a ratio of 1:1 (deionised) water to glycol (such as ethylene glycol or propylene glycol), ora ratio of 2:1 deionised water to glycol, or a ratio of 3:1 deionised water to glycol, or a ratio of 4:1 deionised water to glycol, or a ratio of 5:1 deionised water to glycol. The heat exchange fluid may be up to 10% glycol in (deionised) water, or 1% glycol in deionised water, or 2% glycol in deionised water, or 5% glycol in deionised water, or 10% glycol in deionised water, or 20% glycol in deionised water, or 30% glycol in deionised water, or 40% glycol in deionised water, or 50% glycol in deionised water. The heat exchange fluid may be a mixture of another type of alcohol (for example, methanol, ethanol, isopropyl alcohol) and deionised water. A solution may be up to 10% alcohol in deionised water, or 1% alcohol in deionised water, or 2% alcohol in deionised water, or 5% alcohol in deionised water, or 10% alcohol in deionised water, or 20% alcohol in deionised water, or 30% alcohol in deionised water, or 40% alcohol in deionised water, or 50% alcohol in deionised water. Coolant fluid may also comprise one or more perfluoroamines, such as Fluorinert. Any water described as deionised throughout may also cover non-deionised water, and vice versa. An aspect of the present invention is an electrochemical device comprising the component of any one of the aspects or embodiments described herein, or a plurality of the components of any one of the aspects or embodiments described herein. Preferably, the electrochemical device comprises a plurality of the component one of the aspects or embodiments described herein. Preferably, each of the plurality of components is arranged such that the first conductive layer and the one or more cathodes of each component face the third conductive layer and the one or more anodes of an adjacent component. Each of the plurality of components is arranged such that the third conductive layer and the one or more anodes of each component face the first conductive layer and the one or more cathodes of a component. Preferably, for each component of the plurality of components, the first conductive layer comprises the first fluid path, the second conductive layer comprises a third fluid path for a heat exchange fluid, the third conductive layer comprises the second fluid path and the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid. At least part of the third fluid path of one component and at least part of the fourth fluid path of an adjacent component at least partially align with each other so as to form part of a single heat exchange fluid path between the two adjacent components. This is a join heat exchange fluid path between the two adjacent components. This path may act to manage the thermal properties of the two adjacent boards. Preferably, at least a portion of the first conductive layer of the cathode plate of one component at least partially overlaps at least a portion of the third conductive layer of an anode plate of an adjacent component. Preferably, at least a portion of the second conductive layer of the cathode plate of one component overlaps and touches at least a portion of the fourth conductive layer of an anode plate of another adjacent component. Preferably, the electrochemical device comprises a plurality of the component one of the aspects or embodiments described herein. Preferably, each of the plurality of components is arranged such that the first conductive layer and the one or more cathodes of each component face the first conductive layer and the one or more cathodes of an adjacent component. Each of the plurality of components is arranged such that the third conductive layer and the one or more anodes of each component face the third conductive layer and the one or more anodes of an adjacent component. Preferably, for each component of the plurality of components, the first conductive layer comprises the first fluid path, the second conductive layer comprises a third fluid path for a heat exchange fluid, the third conductive layer comprises the second fluid path and the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid. At least part of the third fluid path of one component and at least part of the third fluid path of one component on an adjacent component align with each other so as to form part of a single heat exchange fluid path between the two adjacent components. At least part of the fourth fluid path of one component and at least part of the fourth fluid path of one component on another adjacent component align with each other so as to form part of a single heat exchange fluid path between the two adjacent components. Preferably, at least a portion of the first conductive layer of the cathode plate of one component at least partially overlaps at least a portion of the first conductive layer of a cathode plate of an adjacent component. At least a portion of the second conductive layer of the cathode plate of one component at least partially overlaps and touches at least a portion of the fourth conductive layer of an anode plate of another adjacent component. Preferably, components may be arranged so that at least one heat exchange fluid path is formed between two components when adjacent components are at least partially aligned with each other, from fluid paths on both of the adjacent components. The at least one third or fourth fluid path in the conductive layer on an insulating layer of one component and the at least one third or fourth fluid path on a conductive layer of an adjacent component at least partially align with each other so as to form at least part of the at least one heat exchange fluid path between the two adjacent components (a combined heat exchange fluid path between the two components). When found in the conductive layer, the flow path may be open when viewed in isolation as a single layer. Preferably, any overlap or combination of fluid paths described herein may only be a partial overlap, in any axis. Fluid paths formed between two components may be referred to as negative space paths, where the heat exchange pathway is formed in the negative space between two or more components. These offer space saving over other arrangements, because the fluid paths are formed in the copper (and if present a passivation layer) layers between two components, rather than in the core layers themselves. The overall assembly of the layers in the components may be thinner as a result of this particularly as the insulating layer may be thinner than previously as a result. Adjacent components may be at least partially aligned so that the heat exchange fluid paths at least partially align and form at least part of a combined / joint heat exchange fluid paths. This is in addition to the reactant paths also being found in the conductive layer on the other face of the insulating layer, providing further space saving. Preferably, at least one first fluid path of one of the components is at least partially aligned with at least one of the first fluid paths of at least one adjacent component. Preferably, the at least one second fluid path of one of the components is at least partially aligned with at least one of the second fluid paths of at least one adjacent component. Preferably, the first fluid path of one of the components is at least partially aligned with at least part of the second fluid path of the same component. Preferably, the first fluid path of one of the components is at least partially aligned with at least part of the first fluid path of at least one adjacent component. Preferably, the second fluid path of one of the components is at least partially aligned with at least part of the second fluid path of at least one adjacent component. Preferably, the third fluid path of one of the components is at least partially aligned with at least part of the fourth fluid path of the same component. Preferably, the third fluid path of one of the components is at least partially aligned with at least part of the third fluid path of at least one adjacent component. Preferably, wherein the fourth fluid path of one of the components is at least partially aligned with at least part of the fourth fluid path of at least one adjacent component. Preferably any combination of these may be present in a device. Preferably, at least a portion of the second conductive layer of the cathode plate of one component at least partially overlaps and contacts at least a portion of the fourth conductive layer of an anode plate of another adjacent component. Preferably, at least a portion of the second conductive layer of the cathode plate of one component at least partially overlaps and contacts at least a portion of the second conductive layer of an cathode plate of another adjacent component. Preferably, two or more adjacent components both comprise one or more means to conduct electrical current and heat through the insulating layer of the anode plate of one component and the cathode plate of an adjacent component, and wherein these means to conduct electrical current and heat through the insulating layer on both components are at least partially aligned to conduct electrical current and heat through both components. Preferably, the one or more means to conduct electrical current or heat through the at least one insulating layer are also at least partially aligned with those means to conduct electrical current or heat on at least one or multiple adjacent components. Preferably, at least two components in the device are laminated together. Preferably, the components in the device are mechanically pressed or compressed together, preferably with a sealant. Use of an epoxy resin prepreg may maintain compression of the gas diffusion layer of the MEAs, a critical component in maintaining device performance as it provides a sufficiently low resistance electrical path without compromising distribution of reactant fluids. Preferably, the electrochemical device is a fuel cell, an electrolyser, a sensor, a hydrogen sensor or a redox flow battery. Preferably, the electrochemical device is any electrochemical device utilising PCBs to construct components of the electrochemical device. Preferably multiple different components in an electrochemical device may comprise any one or more of the components described herein. Preferably, each component described in any aspect of the invention described herein is connected to an electronic circuit to produce an electrical output or input, and wherein the connection between each component and the electronic circuit is individually switchable. Preferably, the connection between each component in the fuel cell and an electrical line can be controlled by a switch mechanism such as a field-effect transistor (FET) switch, providing power handling and control directly at the individual level. Each of these switches can be controlled by individual control lines. This can be by providing a switch on each component. Preferably, when a fuel cell the oxidant fluid described in any aspect of the invention described herein is air and / or the reductant fluid is hydrogen gas. Preferably, when an electrolyser, water or an electrolyte is used as input fluid. On the anode, oxygen generated and on the cathode hydrogen is produced. Thus, there may be fluids both flowing towards and away from the electrodes in a component or device. Preferably, when the electrochemical device is a fuel cell, each fuel cell board may have a power rating of at least 1W. Preferably, each fuel cell board may have a power rating of up to 1000W. Preferably, each fuel cell board may have a power rating of 1W to 1000W. Preferably, a fuel cell comprising multiple fuel cell boards may have a power rating of at least 2W. Preferably, a fuel cell comprising multiple fuel cell boards may have a power rating of up to lOOOkW. Preferably, each fuel cell a fuel cell comprising multiple fuel cell boards may have a power rating of 2W to lOOOkW. Preferably, when the electrochemical device is an electrolyser, each electrolyser component may have a power rating of at least 20W. Preferably, each electrolyser component may have a power rating of up to 5kW. Preferably, each electrolyser component may have a power rating of 20W to 5kW. Preferably, an electrolyser comprising multiple electrolyser components may have a power rating of at least lOkW. Preferably, an electrolyser comprising multiple components may have a power rating of up to 1MW. Preferably, each electrolyser comprising multiple components may have a power rating of 5kW to 1 MW. Preferably, the at least component may comprise at least one electrical connector configured to connect the at least one anode to the at least one cathode through the at least one ion permeable membrane. Connecting the anode to the cathode with the electrical connector through the ion permeable membrane allows an electrical current to flow in a direction along the plane of the membrane. Preferably, at least one through-membrane electrical connector may connect the electrodes across the membrane in a region where an anode and a cathode at least partially overlap, and the at least one through-membrane electrical connector may for example be produced by a homogeneous chemical deposition process. An aspect of the present invention is the use of an electrochemical device or component for an electrochemical device of any embodiment or aspect described herein. An aspect of the present invention is a component for an electrochemical device. It may comprise an insulating layer comprising at least one conductive layer, where the conductive layer comprises a fluid path for a reactant fluid. This fluid path supplies reactant to an MEA, which may be present in the component. There may be a GDL or another layer between the MEA and the first fluid path. The component may comprise multiple first fluid paths. The insulating layer may comprise a second conductive layer on the other side of the insulating layer, this second conductive layer may comprise a further fluid path for a heat exchange fluid. Preferably, the insulating layer and conductive layer are a PCB, preferably wherein the insulating core is FR.-4 and the conductive layer is copper. This may be a component for any type of electrochemical device where fluid flow temperature control is important, and it would be advantageous to utilise reactant and heat exchange fluid flow in such a device. For example, this might be for a fuel cell as described herein. Or, this could be for an electrolyser or other such electrochemical device. The component may also comprise a passivation layer on the conductive layer. The conductive layer may be metal. Preferably, the one or more insulating layers can comprise PCB layers, as described in the first aspect described above. Preferably, at least one of the first fluid path or the second fluid path or the third / further fluid path is substantially linear. Preferably, at least one of the first fluid path or the second fluid path is serpentine. Preferably, the component comprises multiple first fluid paths and / or multiple second fluid paths, or any flow path geometry as described for the first aspect of the invention. Preferably, any one or more of the flow paths are serpentine or substantially linear, or substantially parallel to other flow paths in the same layer. Preferably, one or more of the flow paths comprise flow restrictions or flow directional changes to perturbate fluid flow at defined intervals and / or to increase mass flow velocity and / or a change in pressure drop. Preferably, one or more flow paths are convergent flow fields with tapered channels dimensions. These can introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemical device / board. Preferably, one or more of the flow paths have cascade-type fractal designs, where the flow is split down a number of levels before it reaches the electrodes. These can help maintaining a fixed pressure throughout the surface of the MEA and could promote a uniform fuel utilisation relative to more traditional designs. Preferably, one or more of the fluid paths is formed in the conductive layer by electrochemical machining or etching the conductive layer on the layer of insulating material to create a flow path for a fluid. Preferably, the heat exchange fluid has a composition as described for the first aspect. Preferably, the component may also comprise any part of an embodiment of the first aspect of the invention described above. As aspect of the present invention is a method of manufacture of a component for an electrochemical device, wherein the manufacture comprises electrochemical machining, chemically etching a conductive layer on a layer of insulating material, or any other method of removing material from conductive layer on an insulating layer. The component may be a component as described for the first aspect of the invention. The electrochemical device may be an electrochemical device as described in the second aspect of the invention. Preferably, the method comprises electrochemical machining, chemical etching the conductive layer on a layer of insulating material, or any other method of removing material from a conductive layer on a layer of insulating material to create a flow path for a fluid. Preferably, the method comprises creating a flow path for a fluid with a depth at least 5 pm. Preferably, the flow path is the full depth of the conductive layer. Preferably, the insulating layer and conductive layer are a PCB, preferably wherein the insulating core is FR.-4 and the conductive layer is copper. Preferably, the insulating layer and conductive layer together are a PCB. Preferably the method comprises electrochemical machining, chemical etching, or any other method of removing material from a PCB to create a fluid flow path. Electrochemical machining, chemical etching or any other method of removing material from a conductive layer allows the decoupling of the fluid path geometry on opposite sides of the same plate (cathode and / or anode plate), allowing for different fluid pathways on different faces of boards. These methods allow independent creation of flow paths on the same plate but different sides or different parts of a plate. One of the fluid paths may be independently created from one or more of the other fluid paths. Any fluid path may be independently created from another fluid path on the same or another face / side of the same plate. Preferably, the flow path geometry of the first fluid paths is different to the flow path geometry of the second fluid paths. Preferably, the flow path geometry of the first fluid path is different to the flow path geometry of any further fluid paths. The flow path geometry of a fluid path on one face of the component may be different to the flow path geometry of fluid path on the opposing face of the same component. Preferably, one or more of the flow paths comprise flow restrictions or flow directional changes to perturbate fluid flow at defined intervals and / or to increase mass flow velocity and / or a change in pressure drop. Preferably, one or more flow paths are convergent flow fields with tapered channels dimensions. These can introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemical device / board. Preferably, one or more of the flow paths have cascade-type fractal designs, where the flow is split down a number of levels before it reaches the electrodes. These can help maintaining a fixed pressure throughout the surface of the MEA and could promote a uniform fuel utilisation relative to more traditional designs. Preferably, the method may comprises making at least one of the following: multiple first fluid paths which are substantially linear and substantially parallel with each other, multiple second fluid paths which are substantially linear and substantially parallel with each other and / or multiple further fluid paths which are substantially linear and substantially parallel with each other. Preferably, any one or more of the flow paths are serpentine or substantially linear, or substantially parallel to other flow paths in the same layer. Preferably, the first and the second conductive layers are thicker than the first insulating layer. Preferably, one or more of the fluid paths depths is shallower or smaller than the full depth or thickness of the conductive layer, so all three walls of the fluid path are of the conductive layer. Preferably, one or more of the fluid paths is not through the whole body of the conductive layer it is located within. A further aspect of the invention is a component for an electrochemical device produced by the method of this aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which: FIG. 1 shows a schematic side view of a stacked fuel cell of the prior art; FIG. 2 shows a cross-section of a fuel cell of the prior art comprising a stack of fuel cell boards; FIG. 3a shows an expanded embodiment of a fuel cell board of the present invention, FIG. 3b shows an alternative view of the same expanded embodiment of a fuel cell board of the present invention; FIG. 4 shows a schematic representation of how fluid paths may be in the layers / plates of previously described embodiments; FIG. 5 shows a schematic representation of how fluid paths may be in the present embodiments; FIG. 6 to 9 show data and schematics generated to evaluate the fuel cell design performances; and FIG. 10 shows a fuel cell of an embodiment. DETAIL DESCRIPTION Embodiments will now be described in detail with reference to the accompanying drawings. The same reference signs indicate the same or similar features in different figures and embodiment of the invention, although this is only for reference and is not limiting on the invention. In the following detailed description numerous specific details are set forth by way of examples, in order to provide a thorough understanding of the relevant teachings. However, it will be apparent to one of ordinary skill in the art that the present teachings may be practiced without these specific details. The components for electrochemical devices described herein comprise a Membrane Electrode Assembly (MEA) comprising at least one ion permeable membrane, at least one anode, and at least one cathode. The components then comprise a cathode plate and an anode plate which sandwich the MEA. Both of those comprise an insulating layer between two conductive layers. Those insulating layers have conductive layers on at least part of both faces of the insulating later. The cathode plate and anode plate have fluid paths for reactant fluids - the cathode and anode reactant fluids. But, in the designs described herein and unlike previously described designs, the fluid paths for reactant fluids are within or part of the conductive layers on the cathode and anode plates. This has not been described previously. The reactant fluid paths are not located in the insulating layer, but in the conductive layer. Other than for the apertures in the insulant core to allow the reactants to flow from the manifold to the fluid path, the whole cathode and whole anode fluid paths, and all of the flow fields / flow paths allowing fluid to flow from or to the electrodes are located only in the conductive material, not in the insulating / dielectric core. The MEA is located between the first conductive layer of the cathode plate and an equivalent (third) conductive layer of the anode plate so that the cathode reactant fluid path is arranged such that a fluid can flow to or from the one or more cathodes of the MEA and the anode reactant fluid path is arranged such that a fluid can flow to or from the one or more anodes of the MEA. The cathode or anode plate may also comprise heat exchange fluid paths. These may also be located within a conductive layer adjacent to the insulating layer, for example in the conductive layer on the opposite face of each insulating layer to the conductive layer where the reactant fluids are located. Any reference to a conductive layer herein does not necessarily mean a contiguous layer covering the whole face of an insulating layer, those may just be a partial layer or multiple partial layers on an insulating layer. These conductive layers may have fluid paths through their full depth down to the insulating layer, creating gaps between the conductive material "lands" and these gaps maybe arranged to create fluid paths geometries, and the conductive material may not extend to the edge of the insulating layer, and therefore the conductive layers they may just be partial layers. Thus, the insulating layer has no reactant fluid paths in the body of the insulating core, which directly supply reactant to the electrodes ora diffusion layer adjacent to the electrodes. This other than possibly manifolds and inlet / outlet holes / apertures for the reactant and heat exchange fluids to enter or leave the components. But those are outside the active area of the electrodes, and do not supply reactant to the electrodes or a diffusion layer adjacent to the electrodes. This represents a design change from the previously described designs, where the reactant and heat exchange fluid paths were described as being present in the insulating core of the fuel cell boards, for example fully and / or depth routed into those, through both the conductive material and the insulating core. These fluid pathways in the conductive layers may be through the whole conductive material down to the insulating layer, so the walls of the fluid pathway are defined by the conductive material and the floor is the insulating core. Or, the fluid pathways in the conductive material may only be partially through the conductive layer, so that the walls and the floor of the fluid path are all made of conductive material. The anode plate and / or cathode plates (consisting of insulating layers and conductive layers) can be printed circuit boards (PCB), as described herein. PCBs comprising an insulating layer of dielectric material (such as FR.-4 epoxy resin) and a conductive material layer (such as copper) plating on one or more of the outside faces, have the advantage of enabling the components to be manufactured in large quantities and at low cost. A PCB insulating layer of the present invention may comprise multiple PCB layers, referred to as a single insulating layer. Use of insulating materials to construct components for electrochemical devices also enables these components and devices to be constructed without a mass or size penalty which may be present using other materials such as metal. They may also have conductive material plated or filled through holes or other means to conduct electrical current through or across the plates. This allows improved control of current through stacks, as not all of the plates, any present spacers etc need be conductive, like when prior art bipolar plates or conductive metal components are utilised in prior art stacks. Conductive features, such as through holes, e.g. copper plated or conductive resin filled though holes can be focused in specific areas to allow a high level of control of the current through or across components or stacks of components / devices. The conductive layer may comprise a conductive material such as copper, nickel, graphite and optionally a conductive coating such as a passivation layer, as described herein. This may also be considered part of the conductive layers, i.e. the conductive material layer comprises a conductive material and a passivation layer on top, which is also conductive. As used herein, conductive material refers to heat and electrically conductive, insulating and / or dielectric refers to heat and electrically insulating. As used herein, 'board' may refer to a 'component' of an electrochemical device, and vice versa. 'Insulating core' may be used herein to describe the insulating layer between the conductive layers. As an example of electrochemical device which can benefit from the herein described inventions is a fuel cell equipped with a LT PEM. This design can also benefit AEM electrolysers These designs obviate the need for cap layers on individual components, or between individual components in a device. Cap layers were previously required to seal external fluid paths. However, here, no cap layers necessarily need to be present within the stack. Cap layers may still be utilised at the end of the stack to seal the fluid path for the heat exchange fluid adjacent to the current collectors. As described herein, no cap layers are necessary within a stack because either: part of an adjacent component will act to cap or seal adjacent heat exchange fluid paths (when present); or when components are adjacent to other components with heat exchange fluid paths in the conductive material layer the adjacent components may at least partially align with each other so as to form a combined heat exchange fluid path between the two fuel cell boards. Joint, aligned, negative space fluid paths formed between two components to host the heat exchange fluid may be referred to as negative space layers or paths, where the heat exchange pathway is formed in the negative space between two components. These may offer space saving over other arrangements, because the fluid path are formed in the conductive layer comprising a metal, (and if present a passivation conductive coating between two components) rather than in the insulating layers themselves. Components and devices may be thinner as a result, particularly because the insulating core can be much thinner not containing any fluid paths and no cap layers may be needed to contain the fluid. The components and fuel cell designs utilising these components described herein represent a development of the previous fuel cell board and fuel cell designs which utilise insulating layers. The designs herein place fluid paths within the conductive layers on the insulating cores, rather than having some or all of the fluid paths in the insulating core of a fuel cell boards. These may be in comparison to the designs described for example in WO 2023 / 052789, which is incorporated herein by reference. Electrolysers utilising insulating layer components are described for example in WO 2023 / 099877, which is incorporated herein by reference, but not with flow paths contained in the conductive layers. The present designs represent a development of those electrolyte designs. A thinner electrochemical component pitch, (defined as the thickness of an individual electrochemical cell from the top surface of a cathode plate to the top surface of the adjacent cell cathode plate including any heat exchange medium, or defined as a repeating unit within a stack / electrochemical device, the distance between two bipolar plates (cathode and anode plates, heat exchange fluid space, and MEA and any sealant / gasket in between), resulting from the use of fewer layers and / or thinner layers (i.e. fewer PCB layers) increases the power density of the individual component and of the electrochemical device overall. The designs described herein offer an increased efficiency. Having the fluid paths in the conductive layers of the cathode and anode plates allows for the use of a thinner insulating core compared to previous designs, because there is no need for fluid paths to be located (e.g. routed) within the insulating core. The conductive layer may be comparatively thicker compared to previous designs. An increased amount of conductive material, coupled with a thinner insulating core, allows for a great control of the thermal properties of the components and device stacks overall. This results in a more homogenous temperature across the electrochemical component and through an electrochemical stack comprising for example multiple components. This applies to reactant as well as heat exchange (e.g. coolant) fluid paths being located in the conductive layers of the components. More homogenous temperature allows better understanding and prediction of the temperature across components and stacks - allowing for improved heat management. It will be easier to know and / or predict whether electrochemical device components, e.g. fuel cell boards need heating (e.g. at start up) or cooling (e.g. during operation). Sensors detecting the temperature at one place on a component will be indicating closely the temperature across a whole component. Or, sensors combined with easier prediction and more homogenous heat allows for a reduced use or reliance on sensors and more accurate modelling. Users can predict the thermal properties of components better, and heat management systems for devices can better make adjustments to account for these temperature variations. Previously all features of fluid paths in contact with the heat exchange fluid may have consisted of insulating material. Now all surfaces (walls and floor) or two of three surfaces (if the pathway depth reaches the insulating core) in contact with the heat exchange fluid consists of a conductive material. Previously all surfaces (walls and floor) of a fluid path may have consist of insulating material, if located on or within an electrochemical component's insulating core. A higher % of copper in contact with the heat exchange fluid path allows for a faster equalisation of the temperature, because metal and / or other conductive coatings are more efficient at conducting heat either towards or away from areas of an electrochemical device / component. For example, when a heat exchange fluid is used to warm up an electrochemical stack during the start-up procedure, the heat will transfer from the fluid to the conductive metal walls and through any other conductive surface components present in the electrochemical component, for example conductive material plated through holes, to warm up reactants fluids and the MEA, enabling or increasing the rate of the electrochemical reaction. This is more efficient than designs where the reactant and / or heat exchange fluid path are located in the insulating / dielectric core, as previously described. Alternatively, for example, when the heat exchange fluid is needed to cool down the electrochemical component or the electrochemical device stack, i.e. to remove the heat generated by the exothermic electrochemical reaction, the heat is transferred from the surfaces defining the fluid path within the conductive material (either the walls or the walls and the fluid path floor) more readily than in the previously described design where all surfaces defining the fluid path are made of heat insulating material. This helps with heat dissipation during fuel cell operation, e.g. if a hot spot forms in a particular location this can be minimised faster and therefore the temperature of the component can become homogenous faster. A more efficient heat removal mechanism means a fuel cell stack can be operated at higher overall power density, when it is required to operate at higher current / cm2. A higher operating current will increase heat generated within a component, but a more efficient heat management can counter that. A more efficiently regulated MEA prevents or reduces the risk of a thermal runaway and permanent damage to the MEA and to the stack. Additionally, for example in a fuel cell, having a fluid path embedded within the conductive material allows for lateral conductivity, the surfaces of the fluid path will be hotter reducing the formation of liquid water droplets, resulting from the condensation of water touching cooler surfaces then the temperature of the gasstream, making the displacement of any water within the reactant fluid path easier. Displacement of water is advantageous because the accumulation of water in the fluid path may cause mass transfer issues when the reactants cannot reach the MEA to perform the electrochemical reaction, resulting in a drop in the performance of the overall fuel cell. Previously described fuel cell reactant and heat exchange paths, for example those in WO 2023 / 052789, were created by routing or drilling of insulating material layers of the fuel cell components. In the present invention the formation of the fluid path in the conductive layers is achieved by etching the metal layer in a specific design, to favour the diffusion of the fluid within a chosen geometric pattern to achieve a specific pressure drop, reactant fluid distribution, product fluid and heat removal within the electrochemical component and or the electrochemical stack, ensuring all parts of the component are serviced. Copper etching is used in the PCB industry to create circuitry on an electric component, making sure rules of creepage and clearance are respected to avoid any shorting. Here, metal etching is instead used to engineer a geometrical pattern of voids, flow-altering obstructions and distribution features to enhance the thermomechanical properties of the fluid. Such features are tailored to the requirements of the reactant or heat exchange fluid. Once the PTHs have been allocated as required by the chosen geometry of the fluid path and expected performance of the electrochemical device, a photoresist dry film is applied to the metal surface, usually copper, and the image of the desired fluid path is printed on it to mask the areas of the metal which will constitute the structure of the fluid path, and leave exposed the waste copper sections to be etched. The component is then developed to remove the unwanted metal and the residual photoresist in subsequent alkaline and / or acidic chemical spray treatments to reveal the copper forming the fluid path. Multiple treatments maybe required depending on the fluid paths geometrical patterns and / or the thickness of the conductive material. Other techniques maybe use to create the fluid paths such as electrochemical machining reverse plating (ECM anodic dissolution) depending on what is available during the manufacturing of the components. Either of the techniques described above are more accurate industrial processes than routing; permitting the implementation of complicated fluid path designs with a vast array of radii and other features which are prevented by mechanical drilling, due to the inherent constrains of the material removal process and tolerance limitations associated to routing channels. Metal etching the fluid path, especially a complicated one, is significantly faster and cheaper than routing. Additionally, the use of geometrical patterns is not restricted by the physical limitations of stamping metal bipolar board, where whichever feature is incorporated in the fluid pathway on one side of the metal is negatively created in the opposite side of the component. Therefore, a greater variety of shapes could be explored to direct the flow at varying angles within the fluid path to achieve, in the case of the heat exchange fluids the increase / alteration of the heat transfer areas and, in the case of the reactants an optimisation / improvement of the pressure drop, velocity and flow distribution based on the changing concentration of the reactant fluid. After formation of the fluid paths, a further conductive layer, e.g. a passivation layer, can then be applied to the etched conductive layer. Having the fluid pathways in the conductive layers means that varying path thicknesses can be also created, for example part of all of the fluid path may be defined by three conductive surfaces, where the pathway floor comprise some metal or any other conductive material which alters the depth of the fluid path in specific locations, comprising have a conductive material floor / bottom. This also allows introduction of in-path features without the limitation of having a mirror-negative feature on the opposite side of the board (as in prior art metal stamped-out plates) in the fluid path. These board designs are made possible by the current invention because the two conductive layers (metal surfaces) are independent from each other, as they are separated by the insulating core, and therefore can be treated independently. Metal fuel cell boards are typically stamped to produce flow field designs, which results in negative / positive flow pathways design on the sides of a metal board. When flow paths are stamped in metal plates the pathways must mirror, repeat or complement each other as a result of the manufacturing process. Further, in the designs described herein, the flow pathways on opposite faces of the same boards can have different pathways, e.g. different pathway depths or flow field designs. The fluid paths on different faces of the layers described herein can have a different depth or pathway direction and ramification than those on the other face of the same board. Because of the nature of the insulating material core, these electrochemical device components and the individual plates (cathode and anode plates) forming the components may have means to conduct electrical current from one surface of a plate or component to the other. These may for example be "plated through holes" (PTHs) or conductive material filled through holes. An electrically insulating material core may require such a mean so that copper faces either side of an insulating layer can be electrically conductive, as the charge move from the MEAs via electrical connections through the electrochemical device stack and electrical power is outputted from the electrochemical device. The herein described designs and manufacture allows for a greater control in location of and number of means to conduct electrical current from one face of a plate or board to the other (e.g. PTHs). For example, PTHs can be located throughout the board corresponding to the conductive material portions defining the contiguous voids containing the fluid paths. The top surface of the conducting material defining such void can be either in contact with MEAs when the fluid paths accommodate reactants, or in contact with another conductive material surface when the fluid paths accommodate a heat exchange fluid. The exact location of PTHs is a result of the flow pattern necessary electrical clearance and creepage, and of the thermal profile of electrochemical plate. Fewer PTHs may be desired in areas of the board operating normally at lower temperature, and conversely a greater number of PTHs may be desirable in areas of the board operating at greater efficiency, generating more heat, which will need to be removed faster to avoid any thermal runaway. A higher density of PTHs equates to a faster rate of heat removal. In certain designs PTHs could be located both in correspondence of the full depth of the conductive material and in the thin layer of conductive material left adjacent to the insulating core constituting a conductive floor of the fluid channel (normally the void forming the fluid path would have the insulating core as a floor surface). Such A thin layer of conductive material on the floor of flow paths is not needed to conduct charges either to and from the MEA or through the stack via the opposite conductive layers of the electrochemical component to adjacent components, therefore it can be protected from corrosion with a non-conductive coating. PTHs located on the floor of fluid paths, may also distribute heat to the floor of the paths, which might help keep the water in the gaseous state making its removal from the pathways easier. In the same way these thin surfaces may favour the transfer of heat from the heat conductive material to the reactant fluids, as they are equally efficient in transferring heat to the heat exchange fluid to keep the electrochemical device at optimal operational temperature. An increase in means to conduct electrical current from one face of a plate or component to the other (e.g. PTHs) also decreases the overall electrical resistance of the plate and fuel cell board overall. Further, with these designs the thickness of the conductive layer (e.g. metal / s with the optional addition of a passivation coating) can be varied to change the compression over specific areas of the electrochemical components, once established where compression will be needed most. This can be mapped to take into account areas where the pressure is uneven and more pressure is required. The designs described herein bring the thermal conductivity of the electrochemical component (Thermal conductivity (k) refers to the ability of a given material to conduct / transfer heat and it is measured in W / mK -Watts per meter Kelvin-) closer to typical prior art metal boards, whilst having the advantages of utilising an insulating core as middle layer to target heat management rate at different location of the electrochemical component and decoupling the geometry of the reactant fluids from that of the heat exchange fluids. FIG. 3a is a schematic diagram of one view of an expanded component 201 of an embodiment. A fuel cell board is shown to represent the component, but components for other electrochemical devices would follow the same structural principles. Fuel cell board 201 is shown expanded for the purposes of this figure, to show the membrane electrode assembly (MEA) layer 103 comprising MEA 113 separated from cathode plate 101 and anode plate 102. The cathode plate may be the first insulating layer between a first conductive layer and a second conductive layer as described herein. The anode plate may be the second insulating layer between a third conductive layer and a fourth conductive layer as described herein. In fuel cell board 201 the cathode plate 101 and anode plate 102 are laminated together with the MEA 113, the MEA between the cathode plate 101 and anode plate 102 to form a fuel cell board 200. MEA 113 shown here, used in this example, comprises an ion permeable membrane, with one or more electrodes either side of the electrolyte membrane. The cathode(s) on the MEA layer 103 face the cathode plate 101a and the anode(s) face the anode plate 102a. In this embodiment the MEA 113 is laminated between the cathode plate 101 and anode plate 102, but shown separated / expanded in this figure just to show their presence. The MEA may also include a gas diffusion layer, not shown. This shows one embodiment of an MEA suitable for use for the embodiments described here. Other MEA designs, shapes, orientations would be known to a person of skill in the art and understood to be suitable with the present embodiments. For example, multiple cathodes and anodes may be present. Cathode plate 101 and anode plate 102 may be printed circuit boards (PCBs), but in embodiments herein could be layers of any insulating material with a conductive layer either side as described herein The inner faces of both anode plate 102 and cathode plate 102 (101a and 102a respectively) have conductive layers comprising the fluid paths 111, 112. Such layers are coated with a passivation layer to prevent the corrosion of the conductive layer (e.g. the metal) and prevent the poisoning of the MEA. Fluid path 111 are visible on the inner face 101a of the cathode plate 101 in FIG. 3a (flow fields 112 are visible on the inner face 102a of the anode plate 102 in FIG. 3b, not visible in FIG. 3a). Two fluid paths 111 of the multiple parallel flow paths visible are labelled in FIG. 3a. Multiple single fluid paths 111, 112 make up the 'flow field' for each plate, and flow field(s) may be referred to in the singular or as a plurality throughout. Flow fields 111, 112 are shown as parallel flow paths going across each layer from one side of the layers to the other side of the plates 101, 102. The flow fields 111 on the cathode plate 101 may be the first fluid paths as described herein and the flow fields 112 on the anode plate 102 may be the second fluid paths as described herein. Here, the reactant fluid paths 111, 112, are not located in the insulating layer, but in the conductive layer. Other than for the apertures in the insulant core to allow the reactants to flow from the manifold to the fluid path, the whole cathode and whole anode fluid paths, and all of the flow fields / flow paths supplying the electrodes are located only in the conductive material, not in the insulating / dielectric core. The outer faces 101b, 102b of plates 101, 102 are also partially covered in conductive material comprising copper or other metals such as nickel, and a passivation layer, and both comprise the heat exchange fluid paths. As with the reactant flow paths 111, 112, the heat exchange fluid paths are not located in the insulating core, but they are located in the conductive material. The whole heat exchange fluid path is located only in the conductive material and none of it is in any part of the insulating / dielectric core. Reactants are carried within the fluid paths (for example air, hydrogen) to be supplied to the cathodes and anodes. Oxidant fluids flow only to all of or one or more of the cathodes and reductant fluids flow only to all of or one or more of the anodes of each fuel cell board. Reference herein to 'oxidant fluids' refers to fluids that will react at the cathode, oxidants, for example air or oxygen. Reference to 'reductant fluids' herein refers to fluids that will react at the anode, cathode or electrodes described herein. . The MEA 113 is located between the anode plate (first insulating layer) 102 and the cathode plate (second insulating layer) 101 so that when the boards are laminated or mechanically compressed / placed together, the at least one first fluid path 111 of the cathode plate 101 is arranged such that an oxidant fluid can flow to the cathodes of the MEA 113 and the anode plate 102 is arranged so that the at least one second fluid path 112 is arranged such that a reductant can flow to the anodes of the MEA 113. The present arrangement allows effective separation of the reactants for the anodes and the cathodes. Different reactants or electrolytes might flow to or away from the electrodes in different electrochemical devices, but the principles are the same. 'Fluid path', 'fluid channel', 'flow path', 'fluid flow path' 'fluidic path', 'flow field' and 'channel' may all be used interchangeably herein and may be substituted for one another herein. They all refer to means by which fluids can flow or travel along, down or through. Fluids may be substantially directed, either with or without assistance, along fluid flow paths, channels, or other alternative geometries or the like. Reactants may enter one side or corner of the plate and leave via the opposing or opposite side or corner of the plate. Fluid paths 111 are connected manifold 105. Heat exchange fluid paths 302 are connected to heat exchange fluid manifold 107. Various channels / fluids paths / flow field patterns and entry and exit points on a plate to the plate will be known to those of skill in the art. For example, fluid paths can be serpentine, circular, wavy or linear substantially straight (linear) across a plate (such as the channels shown to be parallel with each other in Figure 3 and later embodiments). There herein described fluid paths can have more advance designs and complicated geometries. Among these for example are serpentine and parallel flow fields where narrow channels could be used to deploy high velocity mass flows to effectively remove water accumulation; these can be with or without the addition of 3-D features, introducing flow restrictions or flow directional changes, using different radii, to further perturbate the flow at defined intervals, to alternate an increase in mass flow velocity with a change in pressure drop. Convergent flow fields, with tapered channels dimensions have also been used in industry to introduce a useful pressure drop between inlet and outlet to maximise the efficiency of the electrochemical device board. Etching the fluid paths can also allow the implementation of nature inspire designs which are often analogous to cascade-type fractal designs, where the flow is evenly split down a number of levels before it reaches the electrodes. This could help maintaining a fixed pressure throughout the surface of the MEA and could promote a uniform fuel utilisation relative to more traditional designs, albeit the reactant flowrate needs to be closely monitored to avoid flooding narrower areas of the flow field. Flow fields can enter and leave by the same edge of a plate or opposing sides or corners of the plates, as shown here with the reactant flow paths. It can be advantageous to have flow of reactants enter and leave opposite sides of the plate so that the reactant manifolds can easily be separated on opposing sides of a fuel cell. The etching of the fluid paths with the decoupling of the fluid path geometry on opposite sides of the same plate ( cathode and / or anode plate) within the conductive layer on both sides of the insulating layer, allows for different fluid pathways on different surfaces of plates, for example one surface of a plate may display one or more serpentine flow path and one face may display parallel flow paths with the addition of several 3-D perturbating features. Heat exchange fluid manifold 107 and anode manifold 109 are also visible in FIG. 3a, and these along with cathode manifold 105 may be drilled into the plates after lamination, or possibly before lamination or compression. The manifold holes are visible in all layers of the fuel cell stacks and individual layers throughout, but not all holes are labelled in every figure. Equivalent holes line up with equivalent holes when plates are stacked. Generally, for all embodiments herein, manifolds of any appropriate size, dimension and shape supply and collect the reactants and heat exchange fluids, or any other relevant substances, into and out of the inlets and outlets of fuel cell boards. Vertical channels up and down fuel cell stacks are connected to manifolds along the two opposed edges of the stack, which supply and collect the reactants, heat exchange fluids (e.g. coolants) etc. to and from boards. These may be drilled or routed into the individual boards before or after lamination to other boards. The plates may also have holes drilled for bolting holes, and / or alignment pins can be inserted into these. FIG. 3b is a schematic diagram of an opposing view to FIG. 3a of the same expanded fuel cell board 201. Fuel cell board 201 is shown expanded for the purposes of this figure, to show membrane electrode assemblies (MEAs) 113 separated from cathode plate 101 and anode plate 102. Only inner face 102a of anode plate 102 and outer face 101b of cathode plate 101 are visible in FIG. 3b. The anode fluid paths 112 are visible on the inner face 102a of anode plate 102 (two fluid path 112 are labelled in FIG. 3b but multiple fluid paths 112 are visible). The conductive layers facing the MEA are coated with a passivation layer to prevent the corrosion of the metal / s and prevent the poisoning of the MEA. In FIG. 3b the flow paths 111 for the cathode plate 101 are not visible, they are on the not visible inner face 102a of the cathode plate 102. Anode manifold 105, heat exchange fluid manifold 107 and cathode manifold 105 are also visible in FIG. 3b. A second set of heat exchange fluid paths 302 can be seen in FIG 3b (these specific ones not visible in FIG. 3a), on outer face 102b of anode plate 102. Two paths 302 of the multiple shown are labelled. These connect to heat exchange fluid manifold 107. These supply a heat exchange fluid to the fluid paths on side 102b of anode plate 102. Heat exchange fluid paths 302 may be the third and fourth fluid paths for a heat exchange fluid as described herein. In embodiments herein, heat exchange fluid paths in the conductive layers of adjacent boards may at least partially align with each other, so as to form a combined heat exchange fluid path between the two fuel cell boards. The conductive layers may comprise any combination of copper, copper with an additional metal coating such as Nickel, ENIG or any conductive polymeric and or carbon based conductive passivating coating. Fluid paths formed between two components may be referred to as negative space fluid paths or a negative space layer, where the heat exchange pathway is formed in the space or void between two or more components. The utilisation of this space may offer space saving over other arrangements, because the fluid paths are formed in the conductive layers between two boards, normally used only to carry the current through the stack, therefore exploiting a synergic effect of this new cell structure. Symmetrical designs of heat exchange fluid paths on adjacent boards may be used, which can be advantageous because it enables easier alignment of the conductive means such as PTHs, making the current path shorter and therefore reducing the electrical resistance within the structure and the consequential additional heating of the conductive layers. While fluid paths may be fully aligned, fluid paths may be partially aligned so not all of the path overlaps. This may vary along the flow paths. Parts of equivalent flow paths on adjacent components may not align at all. For example, the alignment may only be aligned with the active area of the MEA. Additionally, or alternatively, flow paths may be partially unaligned or just partially aligned, flow paths on adjacent components may only partially align with each other. Part of the flow path may overlap with the conductive material between the flow paths on the adjacent component (termed lands herein). FIG.4 shows a prior art embodiment, where previously described arrangement of how fluid paths or fluid channels may be in the insulating layer is demonstrated, as described in WO 2023 / 052789. This contrasts with the presently described designs in that the fluid paths are within the insulating core. Fluid paths on the same component may be partially aligned with each other, i.e. fluid paths to supply fluid to the MEA on side of the MEA (e.g. first and second fluid paths as described herein) may be at least partially aligned with each other. This can help sturdiness of components, as the lands between fluid paths would also partially align. Here, reactant flow paths 111,112 and coolant flow path 302 are shown through the whole body of the insulating core 160. Here the depth of each of or both of the reactant flow paths 111,112 and coolant flow path 302 are equal to the thickness of the insulating layer. This means that the fluid channel / flow path / channel is open to both faces or surfaces of the single insulating core 160 shown here. Additional layers of insulating material or additional insulating layers or additional capping layers 150 are present to seal or cap both sides of flow path 302. These may be individually added, or a continuous layer added to cap or cover one or more of the flow paths. But no additional layers of insulating material or additional insulating layers are present to seal or cap at least one side of reactant flow paths 111,112, the sides adjacent the GDL 901, so that reactants can flow or diffuse to the anodes or cathodes. A capping layer of the correct design may be added, or a single capping layer may be added to / laminated with a layer of insulating material and drilled or routed to expose the relevant fluid paths (or both a capping layer and a layer of insulating material may be drilled or routed together to create a fluid path and exposure through the capping layer to said fluid path). The side of reactant flow paths 111,112 not adjacent to the GDL 901 are capped with additional insulating material, here cap layer 150. Here, no fluid paths are in the conductive layers, copper 903. FIG. 5 shows a schematic representation of how fluid paths may be in the conductive layers described herein. Here an insulating core layer 160 is shown, which is equivalent to an 'insulating layer' as described herein. This is a core of insulating material and has a conductive layer on each face. This could be the cathode plate 101 or anode plate 102 as described above, and each plate may be a PCB. The conductive layers comprise a metal layer 903a / 903b and a passivation layer 904 / 904b either side of the insulating core 160. Four insulating layers with conductive layers on both sides are present, representing two anode and two cathode places. Here, cathode and anode plates are adjacent to each other and contact each other. 1001 represents the GDL layer, structure of this and the MEA is not shown. A whole single component can be seen between two MEA / GDL layers 1001, and half another board or module can be seen below a MEA / GDL layer 1001. FIG. 5 shows heat exchange fluid paths 302 in the conductive material layers 903a / 904a, along with reactant fluid paths 111, 112 also in the opposite conductive material layers 903b / 904b. Reactant fluid paths 111, 112 may carry reactants to the cathodes or the anodes as described herein. No fluid path is present in the insulating core 160 (nor in the prepreg 900). Here, there is no adhesion or gluing between the layers, just mechanical compression can hold such an arrangement together in operation. Sealant 906 acts to seal, bond or adhere layers together where show. Sealant could be used through such stacks or layers, or just mechanical compression could be used if appropriate. FIG. 5 shows a central portion of components, without the inlet and or the outlet of the fluid paths visible. The figure shows only three heat exchange fluid paths 302 per layer and two of each reactant fluid paths 111, 112 per layer, but in embodiments herein varying numbers of each could be present in each component or device described herein. Or, just one of each may be present in each layer. These flow paths may have varying designs i.e. patterns, fields, geometries or arrangements as described herein. As can be seen between the two middle plates heat exchange fluid paths are aligned and thus create a combined fluid path between the previously separate components. Here they are shown as fully aligned at this point in the cross section. Fluid paths may be partially aligned so not all of the path overlaps, which may vary along the flow paths, or part of equivalent flow paths on adjacent components may not align algin at all. Means to electrically connect the plates with each are not shown, but these could be for example PTHs which cross insulating layers 160 in alignment with the neighbouring components. PTHs may electrically connects the conductive layers 903 / 904. As shown here, when at least part of the heat exchange fluid paths align at least a portion of the lands between those heat exchange fluid paths on the adjacent component also aligns with and is in contact with equivalent adjacent lands between the heat exchange fluid paths on the adjacent component. With alignment of the lands or non-fluid path part of the boards, the electrochemical device stack can be compressed without crashing areas of the MEA which are unsupported (as where a portion of conductive material from one of the cathode or anode facing the MEA is pressed across the MEA, against a void in the opposite conductive layer of the anode or cathode it may collapse into the void causing the crashing of the softer MEA or the GDL). Alignment of these lands also allows alignment of means to conduct electrical current, e.g. PTHs, through these parts of the components or stacks. Reactant lands may align fully, partially or not at all, allowing the compression of MEAs to be optimized for given materials and applications, whilst over compression or crushing can be avoided. Although perhaps not necessary with these designs, additional layers of insulating material or additional insulating layers may be added to seal or cap one or more of these channels, as described herein. This is adjacent the layer with the flow path for the heat exchange fluid. This acts to seal or cap this path, so that any fluid flowing through these paths will only flow along / through this path, along the intended path, and nowhere else. This layer can be held in place by compression in a stack of such boards or components. Copper plating 903 can carry electrical current between these two layers of insulating material. This layer may be referred to as the further (to the first and second insulating layers forming the cathode and anode plates) insulating layer. These layers may comprise an insulating material layer between two conductive layers, the heat exchange fluid pathways in just one 5 of the two conductive layers on that insulating layer, which may also align with the heat exchange fluid pathways of adjacent components. These cap layers may just be present at the top and / or bottom of a device stack, to cap a stack, so there are not open heat exchange fluid paths. These capping or further insulating layers may be of varying thickness. Capping or further insulating layers as described 10 herein may be rigid layers of insulating material, such as rigid PCBs, or may be thinner flexible layers of insulating material, such as flexible PCBs. These can be copper plated and have a passivation layer on, they would still be flexible. Exemplary dimensions of various components of the fuel cell boards can be found in Table 1: 15 Table 1 Feature Dimension length Insulating core 160 Thickness - 15 pm to 275 pm Conductive layer hosting heat exchange fluid path Thickness - 130 pm to 320 pm Heat exchange fluid path 302 Up to the depth of the conductive layer Conductive layer hosting reactants fluid path Thickness - 130 pm to 320 pm Reactant flow path 111 / 112 Up to the depth of the conductive layer Passivation layer thickness Thickness 15 pm to 60 pm Width of a path example within the heat exchange fluid path 640 pm to 960 pm Width of a solid area (land) example between heat exchange fluid path 640 pm to 960 pm Width of a path example within 400 pm to 960 pm reactant fluid path -cathode- Width of a solid area (land) example between reactant fluid path -cathode- 640 pm to 1140 pm Width of a path example within the reactant fluid path -anode- 640 pm to 960 pm Width of a path example within the reactant fluid path -anode- 640 pm to 960 pm These dimensions are purely exemplary to illustrate dimensions suitable for use with the presently described inventions. Included in Table 1 is a passivation layer. Conductive layers may comprise at least a partial passivation layer, e.g. passivation ink, as described herein. This may have a thickness of 3 pm to 100 pm, preferably 15 pm to 90 pm. For example, for a passivation ink layer this may be 15 pm to 90 pm, for a ENIG layer this may be between 3 pm to 10 pm, preferably 3 pm to 6 pm. Any of the herein described fluid flow paths can be formed within the conductive layer as the flow fields. Preferably they are etched into the conductive layer once the conductive layers and the electrical means through the conductive layers and the insulating layer (cathode and anode plates either side of the MEA) have been completed. The flow fields / paths for the reactants are not located within the insulating layer itself. Heat exchange fluid paths may also be located in the conductive layer. Preferably, 80% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably 90% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably 95% of the fluid paths (reactant and / or coolant) are in the conductive layer, preferably over 90% of the fluid paths (reactant and / or coolant) are in the conductive layer. As can be seen throughout some of the figures herein, a fluid path may provide a fluid path for fluid within a single layer, as opposed to requiring one layer to provide a fluid path, and another layer to provide a sealing face sealing the fluid path (i.e. no cap layers required). The fluid paths may of a depth of up to the thickness or depth of the conductive layer. The fluid paths may be through the whole body of the conductive layer. If in the conductive layer and the thickness of the conductive layer varies, the fluid paths depths will vary with that. When in the conductive layer, the fluid paths may be found of a depth of up to 1mm. Fluid paths may be around 1mm, 0.9mm, 0.8mm, 0.7mm, 0.6mm, 0.5mm, 0.4mm, 0.3mm, 0.2mm or 0.1mm in depth. Fluid paths may be between 1mm and 0.1mm, or between 1mm and 0.3mm, between 0.9mm and 0.4mm, or between 0.8mm and 0.4mm. Preferably the flow paths are 10%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90% or up to the entire depth of the layer. Preferably, the flow path if the geometry of the fluid path requires a thin layer of conductive material to lay on the bottom of the fluid path, this can be of any thickness from 5% to 95% of the conductive layer, preferably 20% to 5% of the conductive layer remains, preferably less than 20% of the conductive layer remains, preferably less than 10% of the conductive layer remains. Preferably 5% of the conductive layer remains. The floor of the channel in the conductive layer may be around 0.1mm thickness. The floor of the channel in the conductive layer may between 0.01 mm and 0.1mm thickness. These parameters and distances may be applied to embodiments here. These embodiments and features may also apply to the component for an electrochemical device described herein. The conductive layer (e.g. metal 903 and passivation 904 layers) could be deposited / plated / coated / printed or otherwise manufactured using techniques known in the art so as to have the flow paths / fields / channels / gaps, or they could be etched, drilled, machined or routed to have the fluid paths / fields / channels / gaps. Plated through holes 120, metal layers 903 and passivation layers 904 are all conductive, so current and heat can pass through the cathode and anode plates and through the cell board to the adjacent board and through the stack. Sealant 906 may also be present in this, and any embodiment described herein. Sealant between / at the edges of boards can prevent heat exchange fluid leakage and can act to stabilise the stack against slippage of modules in use, for example from vibrations. Sealant is just representative here, and the boards may be wider to have more flow paths than shown. For all Figures herein, flow paths and board sizes / thicknesses are not to scale and are adjusted just to show how they could be arranged, real thicknesses, sizes and numbers of paths may vary. As shown here, there may be multiple flow paths in a single board. These embodiments and features, for example flow path arrangements, relative depths etc. may also apply to any component for an electrochemical device described herein. By positioning all the fluid paths within the components conductive layers and using a very thin insulant core the overall cell pitch has been reduced by 50% and the performance over the entire operational window is increased compared to the previous generation design. FIG. 6a shows a polarization performance graph, where the presently described fuel cell stack designs were demonstrated in single cell tests and compared to tests to previous designs. The cell potential and current density are plotted against one another. The solid line shows the present, newer design, the dashed line shows an older design, as described herein. FIG 6b shows how the present design allows for better area specific energy density as the etching enables beneficial flow field features which were not possible in the old design. FIG. 6c illustrates instead how the area specific energy density benefit is coupled with the reduction of the cell pitch of the present design against the old design. The present design implements 50% pitch reduction, an easier and cheaper manufacturing processes and an improved thermal management over the entire area of the component. A ID-model representation was produced, see FIG 7a to 7c to demonstrate that the herein described designs are capable of removing heat power produced by the MEA at high current densities, and capable of transferring the heat effectively to a heat exchange fluid. FIG.s 7a to 7c show ID Thermal Model Estimates for the presently described fuel cell designs compared to earlier designs. For comparison purposes only, these assume the heat moving unidirectionally through material elements from the MEA to the Heat exchange fluid (defined as a coolant when the aim of the fluid is to remove heat from the cell, and conversely as a warming fluid where the heat is instead transferred in the opposite direction such as from the fluid at higher temperature than the surrounding cell to the MEA, for example during cold-start when the electrochemical reaction necessitates a warm MEA to occur). Conductivities for different material elements within a representative heat path are shown. Reference herein to earlier / previous designs refers to those designs earlier from the inventors, where all the fluid paths for reactants and heat exchanged fluids were located in insulating materials, for example as described in WO 2023 / 052789. In these representations, several different materials conductivities such as the GDL, a passivation layer such as carbon ink, copper, a dielectric material, used for the insulant core, such as FR-4 and stainless steel are shown. FIG 7a shows an illustration of the heat pathway across several materials exemplificative of a previous design, where fluid paths could be located in the insulant core, and where the heat was removed by the PTHs in close proximity of the fluid path, rather than by the conductive layer in direct contact with the fluid paths of reactant and of heat exchange fluid. In this design part of the heat pathway account for dielectric material boundaries. FIG. 7b instead shows a representation of the present designs, as described herein where the insulant core is much thinner not having to allocate any fluid paths within. These two designs are compared to a stainless-steel fuel cell board in FIG. 7c, without any dielectric material or any other conductive layer than steel. Table 2 provides the overall Thermal Resistivities of board different constructions. TABLE 2 Parameter Earlier Design (FIG. 7a) Present design (FIG. 7b) Stainless steel (FIG. 7c) Calculated overall Thermal Resistivity (R) -expressed as Kelvin over Watts and defined as the measure of a thermal 0.02923 K / W 0.00887 K / W 0.00685 K / W ability to resist the flow of heat. Representative of the heat pathways. Anode Distance MEA to Heat exchange Fluid Used to compare to present design and stainless steel 75-90% of previous design 40-60% of the present design Cathode Distance MEA to Heat exchange Fluid Used to compare to present design and stainless steel 50-70% of previous design 40-60% of the present design Here, the presently described fuel cell stack designs were shown to be more than three times less thermally resistive than the earlier designs. The thermal resistivity of the present design is 230% lower than the earlier design. The present designs could take advantage of double the heat exchange fluid path surface area compared to what was previously used. The present designs are shown to be much more comparable in terms of thermal conductivity (k) to the stainless-steel fuel cell designs, than the earlier designs with the fluid paths in the insulating core. The Thermal Resistivity of the stainless-steel option is shown to be only 30% lower than the present designs. FIG.s 8a to 8c show an illustration, not at scale, of the positioning of the fluid paths within the boards relative to the material elements used to inform the 1-D model analysis. Once the thermal resistivity for each element was obtained, an electrical analogy for resistors in series and parallel was used to calculate total thermal resistivity. The heat pathways at the anodes and cathodes were assumed to be unidirectional without considering conditions at the boundaries and the bulk conductivity coefficient for composite elements, such as the dielectric core (FR4 conductivity) containing PTHs (copper conductivity) were calculated. Membrane heat power is assumed to be homogenous across the active area. FIG. 8a shows the previous design, with the fluid paths are partially in the insulant layer and in the thin conductive layers. FIG. 8b shows the presently described fuel cell stack design, which has thicker conductive layers hosting all the fluid paths and a thin insulant layer. FIG. 8c shows an exemplary stainless steel fuel cell board, for comparison purposes. This, apart from the GDL, is entirely made of stainless steel. FIG. 9 shows a MEA temperature representation of the designs described herein compared to the earlier designs. The model was validated, and the plot was generated using experimental data (current, voltage, Heat exchange fluid temperatures changes in and out of the system). Operating at the same conditions, the present design's estimated MEA temperature was significantly lower than the earlier designs. The present design's MEA operates only slightly hotter than a 150um stainless-steel fuel cell. The thicker copper conductive layers in the present designs increase the thermal conductivity of the board structure. The thermal conductivity k of copper is significantly higher than stainless steel (Cu= 400W / mK and Stainless Steel = 15W / mK). The present design can significantly reduce the MEA temperature, as the cell board operates at higher voltages (better efficiency) at the same current densities but with a much more efficient cooling, able to keep the MEA at nominal temperature even at high efficiency. This is advantageous as sometimes having an MEA at too high a temperature can be a detriment to fuel cell operation. The 1-D model ignores the heat rejected to gas streams and assumes all heat power is dissipated by the heat exchange fluid, as it was experimentally shown that the heat power dissipated by the gas streams is small compared to the heat exchange fluid, so can be ignored for this simple model. FIG. 9 shows the performance of the previous design, represented by a solid line, compared the present design, dashed line, benchmarked against a stainless-steel fuel cell, displayed as dotted line with crosses. At lower current density the performance of the different designs does not differs significantly, however when the fuel cell is worked harder to extract more electrical power the previous design does not seem to be able to remove the heat generated by the electrochemical reaction fast enough and the temperature of the MEA gradually exceeds the temperature for efficient fuel cell operation. Conversely, the new design thanks to the combination of i) an optimised pitch reduction of 50%, bringing the MEA closer to the heat exchange fluid, ii) the placement the heat exchange fluid within and therefore directly in contact with the conductive layer -guaranteeing a much more efficient in transferring heat to the coolant to be dissipated from the system- and iii) the ability to remove heat directly from the reactant gas-streams, whose fluid paths are also placed in the conductive layer, is able to operate at much higher current density within the whole operational window without exceed even the MEA nominal temperature optimal for the running of the system. In the scenario shown in FIG 9 the inlet temperature of the heat exchange fluid and its mass flow rate were chosen to be within industry standards, easily implemented for state-of-the-art balance of plant recommendations. However, the MEA temperature could be further lowered by increasing the heat exchange fluid flow rate, and / or lower heat exchange fluid inlet temperature. Reference herein to "heat exchange fluid", "thermal management fluid" or a "temperature control fluid", interchangeable herein, refers to a fluid which can be used in an electrochemical device or a component for a fuel cell or other such electrochemical device which can flow near or flow adjacent or flow to contact one or more portions of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. For example, the systems and methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool or heat those anodes. These can act to cool components, for example cool anodes of a fuel cell whilst the fuel cell functions. Or, such heat exchange fluids can act to heat or warm components, for example to heat up an anode component of a fuel cell at the point of fuel cell start up, early in a fuel cell operation timeline / program or in low temperature environments. Heat exchange fluids can be liquids, gases or other such suitable fluids as described herein. Heat can be added or removed from various parts of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. The heat exchange fluid can be used in any electrochemical device where the device temperature regulation is required. In fuel cells for example it may contact one or more portions of the fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. For example, the systems and methods herein can allow a heat exchange fluid to flow through a flow path adjacent or near the anodes of a fuel cell board, acting to cool those anodes. Thermal management using an heat exchange fluid may be employed to maintain the fuel cell board or stack at a certain operating temperature, to operate the system in a more energy efficient manner, to increase the operating lifetime of the system, and / or to provide more efficient fuel cell operation (e.g. allowing a fuel cell to operate within set parameters, not leading to over production or under production of power). All heat exchange fluids known to those of skill in the art would be suitable for the purposes of thermally managing or controlling the temperature of fuel cell boards, fuel cells, components for fuel cells or fuel cell stacks described herein. Particularly, heat exchange fluids can be deionised water, water, or a mixture of water or deionised water and glycol to prevent freezing of the water or water / deionized water and benzotriazole to inhibit copper corrosion, can be used. Other suitable heat exchange fluids and specific additives to avoid freezing and or corrosion of any of the elements of the devices are envisioned, and would be known to a person of skill in the art. For example, a fluid with a ratio of 1:1 deionised water to glycol (such as ethylene glycol or propylene glycol) may be used, or alternatively a ratio of 2:1 deionised water to glycol, or alternatively a ratio of 3:1 deionised water to glycol, or alternatively a ratio of 4:1 deionised water to glycol, or alternatively a ratio of 5:1 deionised water to glycol. A solution may be up to 10% glycol in deionised water, or 1% glycol in deionised water, or 2% glycol in deionised water, or 5% glycol in deionised water, or 10% glycol in deionised water, or 20% glycol in deionised water, or 30% glycol in deionised water, or 40% glycol in deionised water, or 50% glycol in deionised water. Or, a heat exchange fluid may be a mixture of another type of alcohol (for example, methanol, ethanol, isopropyl alcohol) and deionised water. A solution may be up to 10% alcohol in deionised water, or 1% alcohol in deionised water, or 2% alcohol in deionised water, or 5% alcohol in deionised water, or 10% alcohol in deionised water, or 20% alcohol in deionised water, or 30% alcohol in deionised water, or 40% alcohol in deionised water, or 50% alcohol in deionised water. Coolant fluid may also comprise one or more perfluoroamines, such as Fluorinert. Conductive layers could have multiple different fluid paths of different geometries, shapes and / or dimensions, or fluids at different flow rates or different fluid temperatures. Fluids could be at different temperatures or different flow rates in different plates. Overheating of an electrochemical device, e.g. a fuel cell stack can cause problems and cooling of stacks is typically required. This is generally achieved by supplying a heat exchange fluid, for example a coolant fluid that circulates within the stack. For example, in an air-cooled fuel cell heat exchange and reactant fluids may be supplied to the cathode in the same fluid paths. However, in all embodiments described herein, the heat exchange fluid is not part of the same fluid path as the "reactant" to the cathodes (typically cathode reactant is air in air -cooled fuel cell, so air may be the coolant as well as the cathode reactant). This separation of the heat exchange fluid from cathode reactant is advantageous as it provides more control over the flow of reactant to the cathodes, the rate of which will not be determined by the rate of a cooling airflow needed. It also allows improved control of cooling of the anodes. Electrochemical devices can also encounter problems of being at too low a temperature for optimum operation, for example at start-up or in colder environments. A fluid with the purpose of heating or increasing the temperature of various parts of the devices, components or stacks described herein can also be supplied in the same manner as a coolant. This can be in the fluid paths described herein. In some embodiments, the same fluid that will later cool the various parts of the components or devices described herein may also act to initially heat or increase the temperature of those. This could be for example when the device is colder at start-up, the circulating fluid will act to warm the components it is supplied to or past as it is at a higher temperature than other parts, the same fluid will now act to cool the components it is supplied to or past as it is at a lower temperature than the same components. Electrochemical devices may be constructed by layering up of MEAs, cathode and anode plates, and an epoxy resin prepreg (herein 'prepreg'). In construction of a electrochemical device, the MEA is sandwiched between two layers of prepreg, then the cathode and anode plates are laminated either side of those two layers of prepreg. These layers are laminated all together. Plated through holes are then drilled into the anode and cathode plates. After this is complete the final drills and routes expose the anode flow fields and cathode flow fields as well as drills for gas manifolding, bolting holes, and alignment pins can be made. Electrochemical devices and components for those may be constructed of insulating layers sandwiched between conductive layers, for example Printed Circuit Boards (PCB). Such layers can be adhered together into a solid structure using an epoxy-containing glass fibre composite ("prepeg"). The MEAs may be laser bonded onto an insulating layer, a plurality of components can then be laminated together. In certain embodiments the gaps between the electrodes, and the sealing achieved in these gaps by the epoxy resin, prevent separate flows from mixing, i.e. prevent air cooling, reactant and fuel flows from mixing. Use of a sealing materials such as prepreg, and the use of the layers combination aforementioned, such as PCBs ensures that the MEA is sealed from anything not deliberately directed to the components of the MEA by the fluid paths in the conductive layers hosted in the (e.g. anode and cathode plates) directly adjacent to the MEAs. This is an advantage of the herein described technology, it allows quick, simple and cheap construction of such structures. Use of lamination with for example an epoxy resin prepreg also maintains compression of the gas diffusion layer of the MEAs, an important component in maintaining device performance, providing a sufficiently low resistance electrical path without compromising distribution of reactant fluids. Boards which are laminated with a specific lamination process, involving careful pre-cutting and alignment of materials, along with bespoke heating, cooling, pressure and washing cycles. Boards or layers of boards may also be mechanically compressed or pressed together by suitable means. This may be when a whole device is compressed together. This means lamination may not be required in all embodiments. This can be with the use of layers of prepreg or other sealant type materials. Once electrochemical device components are constructed, they can be made into stacks of these components in a modular fashion. For example, when the component is a fuel cell board, these may be stacked to form a fuel cell stack. Stacks may begin and terminate with an endplate which provides compression through the stack as well as sealed ports to connect fluids flows (e.g. reactants, thermal management fluid). A 'stack' may be referred to herein as a device or an electrochemical device. Means to remove excess current can also be used at either end of a device to take off the significantly high current when necessary. A stack can be built with a repetitive sequence of components, e.g. fuel cell boards. The stacks shown throughout may be held together with bolts, or compression bands, which also provide compression for the seals between modules, however any means to hold stacks together compressed, or any means to seal fuel cell boards., Gaskets to seal manifolds or other parts of the stack together can be used, if necessary, but may not be necessary in such a stack. An example of an electrochemical device is a fuel cell such as that shown in FIG. 10. The fuel cell stack 30-1 is encased in a fuel cell casing with end plate 31 visible. Present in this embodiment are 12 fuel cell boards 201. As shown in FIG. 10, the fuel cell has two cathode inlet / outlets 32, two heat exchange fluid inlet / outlets 33 and two anode inlets / outlets 34. Cathode inlets 32 will be connected to a compressed air compressed air canister or an air compressor to supply compressed air to act as an oxidant to react at the cathodes in fuel cell operation. Cathode outlets 32 will be connected to an exhaust to the atmosphere. Sometimes cathode outlets 32 will be connected to an exhaust via a humidifier such that the water produced in the fuel cell can be used to humidify the air going into the stack. This is achieved via passing the incoming and outgoing fluids over a water permeable membrane. Anode inlets 34 will be connected to a hydrogen cannister, to supply hydrogen reactant to the anodes to act as a reductant gas in order to fuel the fuel cell operation. Anode outlets 34 will be connected to an exhaust to the atmosphere or an anode recirculation system. An anode recirculation system can comprise a water trap (to remove accumulated water) and a hydrogen pump or orifice which increases pressure such that any unused hydrogen can be put back into the stack. Endplates 32 act to compress the fuel cell and to seal it, to prevent any fluid leakage in operation. Fuel cells are bolted together to ensure compression. The construction of the components and the electrochemical devices / stacks is described herein in terms of 'horizontal' and 'vertical' planes, in accordance with the embodiments illustrated in the Figures. However, these terms are used for clarity only, and are not limiting on the scope of the invention. It will be clear to the reader that the fuel cell boards can be arranged in any plane, not just the horizontal plane. Further, the term 'directly opposite' is not limited to the electrodes being in register. The anode lies on one face of the polymer electrolyte and lies directly opposite a cathode on the opposite face of the same electrolyte membrane layer. Reference herein to "fuel cell boards" or a "fuel cell board", "board" or "component (for a fuel cell or for an electrolyser)", "electrolyser", "electrolyser stack" may refer to a membrane electrode assembly (MEA) 113 sandwiched between and a cathode plate 101 and an anode plate 102. In the present embodiments, the three layers may be laminated together, or compressed together. The use of these terms is not intended to limit the size, shape or arrangement of the MEA, or other components. No limitation should be placed on the size, shape or dimensions of the components. The term 'insulating layer' used therein refers to an insulating core alone. The cathode and the anode plates of the present design comprise an insulating layer along with one or more conductive layers on either face of the insulating layer. These may be printed circuit boards (PCBs). PCBs for the embodiments may be produced in the known way. Reference herein to 'Printed Circuit Board(s)' or 'PCB(s)' refers to one or more layers of insulating material comprise of one or more dielectric substrates such as an epoxy resin, for example FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, and G-10, preferably the insulating layer comprises FR-4. Multiple layers or boards may be laminated together, for example with an epoxy resin prepreg. Plates or boards may comprise one or more layers of these insulating materials, or one or more PCB boards may make up a single 'insulating layer' as referred to herein. PCB boards comprise areas of conductive material plating. Reference herein to a passivating or passivation layer means an additional layer deposited, coated, printed on the metal / s or other conductive material layer. A passivation layer may be a passivation ink, which may refer to a conductive ink, particularly the ink may have a functional conductive element that is carbon based. The ink acts to provide a low through-plane resistance conductive path between the electrode and the conductive layer facing the MEA while protecting the copper from the potentially corrosive environment of the devices. It does this by passivating any migratory copper which would otherwise cause irreversible damage of the electrolyte / membrane. Further, the ink may be a carbon ink, it may be a silver paste and polyurethane based ink with conductive elements dispersed in it such as carbon nanotubes or gold / silver nanoparticles these and other inks will be known to a person of skill in the art. A passivation layer may comprise gold, silver or nickel, and / or may be an electroless nickel immersion gold (ENIG) layer, an organic solderability preservative layer or an immersion silver plating layer, or any other passivation treatment known in the art. When the fluid paths are formed in copper on insulating layers, the manufacturing steps may consist of first etching away the conductive material (e.g. copper), then depositing a passivation layer which will only be deposited on the conductive material (e.g. copper). The "means to conduct electricity" as referred to herein may be plated through holes or conductive material filled through holes. "Plated through holes" (PTHs) are holes that form a conduit through one or more insulating layers, said conduit running substantially perpendicular to the planar surfaces of the components. These are plated with a conductive material, for example copper, to act as a conduit for electricity. The Plated though holes are necessary because insulating layer (e.g. FR.-4) consists of electrically insulative core so PTHs must be introduced so that electricity can pass from one face of a layer to another, if desired. These may be formed by holes bring drilled through the layer of insulating material (for example a PCB plate) and then lining with a conductive material. For example, they may be lined with a conductive material by an electroplating dip process such that copper lines the edge of each hole. Optional additional steps can occur after electroplating, wherein i) resin can be used fill the remainder of the hole, which is achieved by forcing resin over the PCB layer such that it flows through any holes present; ii) electroplating dip processing again such that the resin filled holes are capped with copper on both sides; and iii) there may be a mild milling process after this to ensure the surface of the PCB is flat. When these are found through PCB layers they can create continuity between two layers of copper plating on either side of the PCB. PTHs may be formed through only certain areas of the insulating layers described herein, or through the plates of the components (for example through just the anode and cathode plates, to be able to carry current to / from the anode / cathode to the outer surface of the plate via the insulating layer to the external conductive layer). PTHs may be formed through the whole component (for example through both the anode and cathode plate and MEA framework with the same hole, to be able to carry current to / from one surface of the component to the other surface of the component), or they may be made through only the cathode and / or anode plate connecting the lands with other conductive surfaces. Holes filled with a conductive material such as a conductive paste or copper may be used in place of or in addition to PTHs. Any reference to alignment or overlap herein may be partial. Partial overlap or alignment may be in more than one axis through a considered component or device. Components can have a single anode and cathode, or a MEA layer may have multiple anode-cathode pairs. The positioning of the fluid paths within the conductive layers for both reactants and heat exchange fluids can be applied to any electrochemical device comprising one or more components each having a single anode-cathode pair, or applied to an electrochemical device comprising one or more components comprising multiple anode-cathode pairs on each component. Anodes can be designed to be aid in the hydrogen oxidation reaction (HOR), be robust to degradation (thermal cycling, voltage, acidic environment), and have a high electrochemically active surface area (ECSA). The same applies for cathode but for the oxygen reduction reaction (ORR). Anodes and cathodes may comprise platinum with a carbon support. Other platinum group metals can be used (Pt, Ir, Os, Pa, Rh, Ru, Pd) as well as non precious metals (NPMs) which have much lower electrochemical activity such as Ni, Fe, Co, Sn). These could vary by ionomer content, PTFE content, catalyst content, composition of the electrodes of by varying the coatings on the electrodes. The materials that the anodes and / or the cathodes themselves are made of may vary. This could be by changing the material the electrodes are made of, i.e. they could be made of graphite, Pt, Ir, a mixture of these or of different mixes or materials across the face of a component. For example, the % of platinum in graphite electrodes might vary across a component to account for variation in condition across the component. The additive materials provided to or with the anodes and / or the cathodes may vary. This could be by addition of IrOx, PTFE, Ru, in varying concentrations across a component for an electrochemical device. Different anodes or cathodes may be used for different electrochemical devices, and would be known to one skilled in the art. Any suitable electrode may be used in any component or device herein, and no limitation should be put on the use of anode or cathode herein. In some embodiments of a fuel cell board, a catalyst layer on the electrodes accelerates a reaction with the fuel (on the anode electrode) and oxidant (on the cathode electrode) to create or consume the ions and electrons. This layer may be made of suitable catalytic material for the reactions of interest, as is commonly understood by a person skilled in the art of fuel cell production. For example, the catalyst layer may be composed of platinum nanoparticles deposited on carbon and bound with a proton conducting polymer (e.g. Nation™). Similarly, for an electrolyser different catalysts may be utilised to drive the electrochemical reaction. MEAs may also comprise one or more gas diffusion layers (GDLs). These may be porous carbon papers such as Sigracet (SGL Carbon), Avcarb, or Toray. These can also be metallic foams or porous metallic materials (e.g. foams or felts). These may comprise aluminium, titanium or stainless steel. The electrolyte membrane may be a proton-exchange membrane (PEMFC), also known as polymer electrolyte membrane (PEM). This maybe either for low temperature applications LT PEM or for high temperature application, HT PEM. This may be fluorinated (for example a sulfonated tetrafluoroethylene based fluoropolymer-copolymer, e.g. Nation™) or a not fluorinated membrane (for example a hydrocarbon membrane, e.g. an lonomr PEMION™ membrane). They can be based on polybenzimidazole and phosphoric acid for high temperature application and high tolerance to CO in the fuel feed. The membrane may be lonomr Pemion, GORE-Select membrane ora Fumatech Fumapem membrane. Or, the electrolyte membrane may be an anion exchange membrane (for example a Fumatech Fumasep FAA-3 membrane). Other such suitable membranes known in the art may be used with the embodiments herein. The electrolyte membrane may be an anion exchange membrane (AEM), for example in an electrolyser. For fuel cell boards, the reactant fluid may be oxygen gas, air or pressurised air or any other suitable fluid which would be oxidised at the cathodes. As described above, the reactant fluid for the cathodes may be air draw in from the atmosphere outside the fuel cell by means of a fan or air compression device. Although the invention as exemplified uses hydrogen as the reactant fuel (i.e. the reductant gas for the anodes), the fuel cells could be used with all suitable pressurised fluids. As used herein "fluid" refers to a substance that has no fixed shape and yields easily to external pressure, for example a gas or a liquid. Fuels for use with the systems and methods as described herein are fluids. These fuels can be hydrogen or a hydrogen-containing mixture, or a hydrocarbon or hydrocarbon derivative. Fuels could be other gaseous fuels, such as methane or propane. Fuels could be other gaseous fuels, such as methane or propane and fluids include oxidants such as air and oxygen. For electrolysers, an electrolyte may be supplied to one or more of the electrodes and referred to as the 'reactant' herein. This may be water or another electrolyte solution such as a 1% potassium hydroxide (KOH) water electrolyte. In an electrolyser, the resultant products (e.g. water and gases produced, H2 and O2) may travel in the fluid channels away from the electrodes. Fluids paths may be used to supply or remove fluids from the electrodes described herein. Electrolysers may further comprise cathode transport layers and an anode transport layers. These are porous so are sometimes known as porous transport layers (PTLs). For example, a cathode transport layer may be NiFe on Nickel felt and the anode transport may be MoCa on Carbon felt. Electrolysers may have a catalyst containing layer or catalyst present somewhere on either side of the ion exchange membrane, then Gas Diffusion Layers (GDLs) or transport layers either side of the ion exchange membrane over or comprising the catalyst containing layers. The component described herein may also be for a redox flow battery or hydrogen sensor electrochemical device, wherein those devices comprise components with insulating layers and conductive layers where flow paths may be located. The electrochemical device as described herein may be a redox flow battery or hydrogen sensor. The hydrogen sensor may be a hydrogen sensor as disclosed in WO 2022 / 167793, the contents of which are incorporated by reference herein. The construction of electrochemical device cells from PCBs and their advantages are further described in WO2012 / 117035, WO2013 / 164639, WO2023 / 099877 WO 2023 / 052789 which are incorporated herein by reference. The fuel cells and fuel cell boards / components described herein can be capable of, any envisioned power output for a fuel cell stack. Each fuel cell board may have a power rating of at least 1W. Each fuel cell board may have a power rating of up to 1000W. Each fuel cell board may have a power rating of 1W to 1000W. A fuel cell comprising multiple fuel cell boards may have a power rating of at least 2W. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of up to lOOOkW. Preferably, each fuel cell comprising multiple fuel cell boards may have a power rating of 2W to lOOOkW. But, any power rating is merely representative of current embodiments, and the rating may vary from these described as just exemplary. An electrolyser or electrolyser board / cell / component may have a power rating of at least 20W. Each electrolyser component may have a power rating of up to 5kW. Each electrolyser component may have a power rating of 20W to 5kW. An electrolyser comprising multiple electrolyser components may have a power rating of at least lOkW. An electrolyser comprising multiple components may have a power rating of up to 1MW. Electrolyser comprising multiple components may have a power rating of 5kW to 1 MW. The systems and methods can be used with pressurised fuel storage units or containers, as are well known in the art. The fuel can be stored in a pressurised storage unit, for example a bottle or canister. These can be, for example at a pressure of between 700 and 300 bar. It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure.

Claims

1. A component for an electrochemical device, the component comprising:i) a Membrane Electrode Assembly (MEA) comprising at least one ion permeable membrane, at least one anode, and at least one cathode, wherein the one or more anodes are arranged on a first surface of the ion permeable membrane and the one or more cathodes are arranged on a second surface of the ion permeable membrane;ii) a cathode plate comprising a first insulating layer between a first conductive layer and a second conductive layer, the cathode plate comprising a first fluid path;wherein the first conductive layer comprises the first fluid path; andiii) an anode plate comprising a second insulating layer between a third conductive layer and a fourth conductive layer, the anode plate comprising a second fluid path,wherein the third conductive layer comprises the second fluid path,wherein the MEA is located between the first conductive layer of the cathode plate and the third conductive layer of the anode plate so that the first fluid path is arranged such that a fluid can flow to or from the one or more cathodes and so that the second fluid path is arranged such that a fluid can flow to or from to the one or more anodes.

2. The component of claim 1, wherein the second conductive layer comprises a third fluid path for a heat exchange fluid and / or wherein the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid.

3. The component of claim 1 or claim 2, wherein no part of the part of the first fluid path from which or to which fluid flows to or from the cathodes is in or through the first insulating layer, and / or no part of the part of the second fluid path from which or to which fluid flows to or from the anodes is in or through the second insulating layer.

4. The component of any one of claim 2, wherein no part of the third fluid path and / or the fourth through path is in or through first insulating layer or the second insulating layer.

5. The component of any preceding claim, wherein the cathode plate is a PCB and / or wherein the anode plate is a PCB, preferably wherein the insulating layer comprises one or more dielectric substrates, preferably an epoxy resin, preferably one or more of FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene or G-10, preferably the insulating layer comprises FR-4.

6. The component of any preceding claim, wherein at least one of or both of the cathode plate and the anode plate comprises one or more means to conduct electrical current and heat through the insulating layer, preferably wherein the means to conduct electrical current and heat through the insulating layer are plated through holes or filled through holes.

7. The component of claim 6, wherein the one or more means to conduct electrical current and heat through the insulating layer are located in the floor of one or more of the fluid paths located in the conductive layer of the anode plate and / or the cathode plate.

8. The component of claim 6 or claim 7, wherein the one or more means to conduct electrical current and heat through the insulating layer are located in the area between one or more of the fluid paths located in the conductive layer of the anode plate and / or the cathode plate.

9. The component of any preceding claim wherein the one or more fluid paths is formed by electrochemical machining or chemical etching or any other method of removing material from the conductive layer.

10. The component of any preceding claim, wherein the first and / or the second conductive layers are thicker than the first insulating layer, and / or wherein the third and / or the fourth conductive layers are thicker than the second insulating layer.

11. The component any preceding claim, wherein each conductive layer has multiple flow paths and the flow paths:i) are serpentine, substantially linear, or substantially parallel to other flow paths in the same layer;ii) comprise flow restrictions or flow directional changes to perturbate fluid flow at defined intervals and / or to increase mass flow velocity and / or a change in pressure drop;iii) are convergent flow fields with tapered channel dimensions; and / oriv) have cascade-type fractal designs, where the flow is split down a number of levels before it reaches the electrodes.

12. The component of any preceding claim, wherein:i) the flow path geometry of the first fluid path is different to the flow path geometry of the second fluid path; and / orii) the flow path geometry of the first fluid path is different to the flow path geometry of the third fluid path, and / or the flow path geometry of the second fluid path is different to the flow path geometry of the fourth fluid path, wherein the flow path geometry of a fluid path on one face of the anode plate and / or the cathode plate is different to the flow path geometry of fluid path on the opposing face of the same anode plate or cathode plate.

13. The component any preceding claim, wherein one or more of the fluid paths depths is shallower than the full depth or thickness of the conductive layer, so all three walls of the fluid path are of the conductive layer, wherein one or more of the fluid paths is not through the whole body of the conductive layer it is located within.

14. An electrochemical device comprising the component of any one of claims 1 to 13 or a plurality of the components of any one of claims 1 to 13.

15. An electrochemical device comprising a plurality of the component of any one of claims 1 to 13, wherein each of the plurality of components is arrangedsuch that the second conductive layer and the one or more cathodes of each component face the fourth conductive layer and the one or more anodes of an adjacent component.

16. An electrochemical device comprising a plurality of the component of any one of claims 1 to 13, wherein each of the plurality of components is arranged such that the second conductive layer and the one or more cathodes of each component face the second conductive layer and the one or more cathodes of an adjacent component.

17. The electrochemical device of claim 15, wherein for each component of the plurality of components, the first conductive layer comprises the first fluid path, the second conductive layer comprises a third fluid path for a heat exchange fluid, the third conductive layer comprises the second fluid path and the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid, andwherein at least part of the third fluid path of one component and at least part of the fourth fluid path of an adjacent component at least partially align with each other so as to form part of a single heat exchange fluid path between the two adjacent components.

18. The electrochemical device of claim 16, wherein for each component of the plurality of components, the first conductive layer comprises the first fluid path, the second conductive layer comprises a third fluid path for a heat exchange fluid, the third conductive layer comprises the second fluid path and the fourth conductive layer comprises a fourth fluid path for a heat exchange fluid,wherein at least part of the third fluid path of one component and at least part of the third fluid path of one component on an adjacent component at least partially align with each other so as to form part of a single heat exchange fluid path between the two adjacent components; and / orwherein at least part of the fourth fluid path of one component and at least part of the fourth fluid path of one component on another adjacent component at least partially align with each other so as to form part of a single heat exchange fluid path between the two adjacent components.

19. The electrochemical device of any one of claims 15 to 19, wherein the first fluid path of one of the components is at least partially aligned with at least part of the second fluid path of the same component, and / orwherein the first fluid path of one of the components is at least partially aligned with at least part of the first fluid path of at least one adjacent component, and / orwherein the second fluid path of one of the components is at least partially aligned with at least part of the second fluid path of at least one adjacent component, and / orwherein the third fluid path of one of the components is at least partially aligned with at least part of the fourth fluid path of the same component and / orwherein the third fluid path of one of the components is at least partially aligned with at least part of the third fluid path of at least one adjacent component and / orwherein the fourth fluid path of one of the components is at least partially aligned with at least part of the fourth fluid path of at least one adjacent component.

20. The electrochemical device of claim 15 or claim 17, wherein at least a portion of the second conductive layer of the cathode plate of one component at least partially overlaps and contacts at least a portion of the fourth conductive layer of an anode plate of another adjacent component and / or wherein at least a portion of the second conductive layer of the cathode plate of one component at least partially overlaps and contacts at least a portion of the second conductive layer of an cathode plate of another adjacent component.

21. The electrochemical device of any one of claims 15 to 20 wherein two or more adjacent components both comprise one or more means to conduct electrical current and heat through the insulating layer of the anode plate of one board and the cathode plate of an adjacent board, and wherein these means to conduct electrical current and heat through the insulating layer on both components areat least partially aligned to conduct electrical current and heat through both components.

22. The use of an electrochemical device or component for an electrochemical device of any preceding claim.

23. The electrochemical device of any one of claims 14 to 22, wherein the electrochemical device is a fuel cell, an electrolyser, a hydrogen sensor or a redox flow battery.

24. A method of manufacture of a component for an electrochemical device, wherein the manufacture comprises electrochemical machining, chemically etching a conductive layer on a layer of insulating material or any other method of removing material from conductive layer on an insulating layer.

25. The method of claim 24, wherein the method comprises electrochemical machining, chemically etching the conductive layer on a layer of insulating material, or any other method of removing material from conductive layer on an insulating layer to create a flow path for a fluid, optionally wherein the method comprises creating a flow path with a depth at least 5 pm, or wherein the method creates a flow path the full depth of the conductive layer.

26. The method of claims 24 or claim 25, wherein the insulating layer and conductive layer are a PCB, preferably wherein the insulating core is FR.-4 and the conductive layer is copper, or wherein the method comprises electrochemical machining, chemically etching, or any other method of removing material from a conductive layer on a PCB.

27. A component for an electrochemical device produced by the method of any one of claims 24 to 26.s

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