Patent Description:
There is an increasing need for embedding touch-sensitive and/or pressure-sensitive devices and functions into conventionally passive objects and surfaces. Developments in this area are helping human-machine interactions become seamless with everyday life. They are also playing an important role in acquiring new knowledge in academic areas, collecting useful research data, and driving businesses to discover new insights of consumer behaviour.

A growing area of interest is the ability to continuously monitor, through novel sensing devices, the varying pressure exerted by various parts of the human body on objects that a user naturally interacts with on a daily basis. This can be used to actuate parts of a system in response to a detected behaviour and/or gather data that can later be analysed to provide useful feedback to an end user. In particular, foot pressure monitoring has found applications in multiple areas, including biomedical diagnostics, prevention of foot ulcerations (e.g. in a diabetic person's foot), physical rehabilitation, sports performance training, injury prevention, and electronic games. By determining the distribution of static and dynamic pressure forces exerted by a person's body through their foot on a shoe sole, one can determine and improve balance, detect excessive pressure in specific areas of the foot, analyse gait stability, detect mobility patterns to understand a user's behaviours and actions, and monitor posture. Similarly, monitoring pressure exerted by a person's body on a seat has applications in the automotive industry, e.g. to monitor a user's comfort, posture and overall behaviour while driving. Seat design is fundamental to preventing issues related to bad sitting posture, and gathering data about sitting behaviour through pressure maps can help manufacturers to improve seat design and comfort and driver's safety. In addition, pressure mapping opens up possibilities of detecting different driving conditions and providing active feedback to the user.

These emerging applications present new challenges in the design and fabrication of pressure mapping devices due to the need of flexible and durable devices capable of naturally following movements of users during daily activities, and simple cost effective ways to obtain high resolution measurements.

Common solutions for producing accurate pressure maps of the foot, such as those described in <CIT> and <CIT>, implement flexible XY sensor array configurations comprising multiple discrete force/pressure sensors. These solutions utilise multiple layers with a large number of electrical components, interconnects/traces and fabrication steps. The individual sensors that make up the XY sensor array are typically split between multiple sensing layers (e.g. one for X positions and one for Y positions) that require assembly and overlay, and each layer of the device typically requires different conductive/non-conductive materials and properties, coatings (e.g. pressure-sensitive coatings), printed conductive tracks/traces and fabrication techniques/steps. As such, these sensor array solutions inherently present complications for device fabrication. In addition, the logic behind array sensing systems is based on the miniaturisation and multiplication of the sensing points, adjusted in two separate directions designed to intersect to provide XY resolution. This approach presents design limitations, particularly upon increasing the spatial resolution as the conductive traces need to be narrowly fitted into the available spaces with limited margin for error, as shown in <CIT>.

Similarly, solutions developed for seat pressure mapping have used a plurality of printed conductive traces ending in sensing points on a sensing layer to measure localised pressure and forces. For example, <CIT> discloses an apparatus for detecting seat occupancy based on measuring pressure-induced changes in resistance of a sensing layer composed of multiple layers of resistive and conductive materials and coatings. Pressure location is determined by measuring resistance changes between pairs of sensing points on opposing sides of the sensing layer. Therefore, a considerable amount of resistive material, sensing points and printed traces are needed to achieve high-resolution pressure mapping, which in turn increases device complexity and fabrication/material costs.

In wearable device and/or seating/bedding applications where surfaces are subject to constant and repeated movements and stresses, devices incorporating complicated sensor arrays, conventional printed traces and/or coatings may be prone to deterioration through breakage and/or de-lamination which may ultimately limit the commercialisation in industries such as consumer electronics, wearable and healthcare products and automotive interiors.

To achieve mass-production of such pressure mapping devices, there is therefore a need for greatly simplified sensing systems that provide high-resolution pressure mapping with minimal sensor elements, and can be produced with affordable materials and fabrication processes.

Aspects and embodiments of the present invention have been devised with the foregoing in mind.

Related prior art includes <CIT>, <CIT>, <CIT>, and <CIT>. <CIT> discloses a sensor device comprising a layer of electrically conductive material and a layer comprising an electronic connector and/or circuitry, with an insulating barrier provided between the layer of electrically conductive material and the circuitry layer configured to selectively permit the layer of electrically conductive material to contact the circuitry layer to produce one or more electrical signals in response to pressure or force applied to the sensor device urging the layer of electrically conductive material towards the circuitry layer. A change in the electrical signals is made in response to movement of a conductive object across the sensor device. The insulating barrier may have one or more apertures therein. The electrical signal may be a voltage or a capacitance. The sensor device may provide analogue X and Y position sensing and/or Z-direction pressure/force sensing. The circuitry layer may comprise a printed circuit board. The conductive material may comprise one or more user interactive areas which may take the form of a push or click button comprising a projection, recess or insert.

<CIT> discloses an electronic device with a force sensing device. The electronic device comprises a user input surface defining an exterior surface of the electronic device, a first capacitive sensing element, and a second capacitive sensing element capacitively coupled to the first capacitive sensing element. The electronic device also comprises a first spacing layer between the first and second capacitive sensing elements, and a second spacing layer between the first and second capacitive sensing elements. The first and second spacing layers have different compositions. The electronic device also comprises sensing circuitry coupled to the first and second capacitive sensing elements configured to determine an amount of applied force on the user input surface. The first spacing layer is configured to collapse if the applied force is below a force threshold, and the second spacing layer is configured to collapse if the applied force is above the force threshold.

<CIT> discloses a touch sensor that is configured to measure input applied to the sensor from a user. Some implementations involve the measurement of changes in capacitance between pairs of adjacent patterned electrodes to detect input at a touch sensor.

<CIT> discloses a pressure and touch sensitive panel, comprising: at least one elastic and dielectric element; and an enclosed force sensitive electrode located by one side of the elastic and dielectric element. The enclosed force sensitive electrode comprises multiple electrical wiring points for connecting to a touch sensitive processing apparatus for the pressure and touch sensitive panel.

According to a first aspect of the invention, there is provided a pressure sensing device as defined in claim <NUM>. The device comprises a first electrode and a second electrode. The first and second electrodes are spaced apart and separated from each other by a distance. The first electrode and the second electrode are formed of or comprise a unitary piece of non-metallic conductive material. The first electrode and/or the second electrode may be formed of or comprise a moveable and/or deformable and/or flexible non-metallic conductive material (e.g. conductive plastics, foams, and/or rubbers, etc.), such that the distance is changeable in response to a pressure or force applied to or on the first and/or second electrode (at one or more locations). The change in distance may be uniform or non-uniform. The term "non-metallic" conductive material used here and throughout means a material that is not a metal such as gold, silver or aluminium. The device further comprises a measurement module connected or connectable to the first and/or second electrode at one or more sensing points (or a plurality of sensing points) on said electrode. The measurement module is configured to measure, at one or more of the sensing points, a change in an electrical signal in response to a pressure or force applied on or to the first and/or second electrode, e.g. that changes or reduces the distance (e.g. in one or more locations). The electrical signal is a change in capacitance between the first and second electrode. The measurement module is configured to measure the change in capacitance at each sensing point individually, and at all sensing points simultaneously. The measurement module is configured to map each measurement obtained from an individual sensing point to a distance of the applied pressure/force from said individual sensing point. The measurement module is configured to determine the location, area and/or amount of the applied pressure on the first and/or second electrode from the individual measurements and mapped distances. The measurement module is also configured to determine the amount of applied pressure from the simultaneous measurement. The amount of applied pressure may be a relative value or an actual pressure value.

The space between the first and second electrode may be at least partially filled or occupied by a non-conductive, compressible and/or flexible spacer layer or material. Alternatively, the distance between the first electrode and second electrodes may be or comprise one or more gaps. The gap(s) may span the distance. The gap may be or comprise an air gap, empty space or a void. The first and second electrodes may be spaced apart and/or separated from each other by one or more gaps. The gap(s) may be changeable and/or closable in response to a pressure or force applied to the first and/or second electrode. The measurement module may be configured to measure, at one or more of the sensing points, a change in an electrical signal in response to a pressure or force applied on or to the first and/or second electrode, e.g. that changes, reduces or closes one or more of the gaps.

The device uses one or more non-metallic conductive electrodes to achieve pressure sensing without traditional metallic electrode sensors. The use of non-metallic conductive materials for the first and/or second electrodes has a number of advantages over conventional sensing technologies using sensors with metal electrodes. The material cost and weight is significantly lower than that of conventional metal electrode materials (such as a gold, silver or aluminium). The non-metallic conductive materials may be mouldable. Therefore, manufacture/assembly of the sensor device is simplified and the associated manufacture/assembly cost is reduced. In addition, the first and/or second electrodes can be formed and/or moulded into almost any arbitrary size, shape or three-dimensional (3D) form due to the nature of the moulding process. This has a number of practical and functional advantages:.

Overall, the design freedom for the sensor device itself is significantly increased.

As such, in use, a pressure or force applied directly or indirectly to the first and/or second electrode that causes the first and/or second electrode to deform and change/reduce the distance/gap between them causes a change in capacitance that can be measured by the measurement module at the sensing points (individually and/or simultaneously). Based on the position of each sensing points on the first and/or second electrode and the magnitude of the signal measured at each respective sensing point, the location, area and/or amount of the applied pressure/force can be determined.

The device may be used for a number of pressure sensing applications including, but not limited to, seating and shoe-sole pressure-sensing. Conventional seating and shoe-sole pressure-sensing devices rely on metal electrode materials and metal-based electronic devices and therefore require additional electronic components in order to incorporate pressure-sensing functions to a traditionally non-sensor object (e.g. a shoe sole). Conventional sensor approaches do not take advantage of the object/products' innate materials, such as polyurethane (PU) foam, ethylene vinyl acetate (EVA) and rubber, as the sensor electrode itself. Manufacturers and technology adopters are therefore required to implement additional assembly processes which can be foreign to their original manufacturing processes bringing higher risks and costs.

The determined location of the applied pressure or force may be or comprise a single point or coordinate. The determined area of the applied pressure or force may be or comprise a spatial extent and/or shape of the applied pressure profile. The area may have location. For example, a pressure or force may be applied at a given location over a large area or a small area. The location of the area may be may correspond to the centre of the area. The amount of applied pressure or force may be or comprise a value positively related to the magnitude of the applied pressure or force. The amount of applied pressure or force may be a qualitative value (e.g. a normalised or relative value) or a quantitative value (e.g. an actual pressure or force value). Where quantitative data is required, the device may be calibrated using known values of applied pressure or force such that the capacitance measurements can be converted to a pressure or force value using a pre-determined relationship.

Where there are multiple locations/areas, an area and/or a distribution of the applied pressure or force, the measurement module may be configured to determine a plurality of locations, areas and/or amounts of the applied pressure and map the pressure distribution. In this way, the device may be or comprise a pressure mapping device. The measurement module is configured to map each measurement obtained from an individual sensing point to a distance or proximity of the applied pressure/force from said individual sensing point. The measurement module may be configured to determine the location (e.g. XY or absolute) of the applied pressure on the device from the mapped distances. The measurement module may be configured to determine the area or shape of the applied pressure on the device from the mapped distances. For example, the mapped distances may correspond to the locations of the boundary of the area. The location of the area can then be determined from the boundary locations. With knowledge of the relative location of each sensing point on the first and/or second electrode, this information can be used to build up a pressure area profile.

The first and/or the second electrode may be formed of or comprise a non-metallic conductive thermoformable material, and/or may be formed by a moulding process.

Suitable materials for the first and/or second electrode(s) may include but are not limited to conductive plastics, conductive rubbers, conductive polymer materials and conductive foams, such as conductive acrylonitrile butadiene styrene (ABS) or conductive PU, conductive EVA, conductive thermoplastic elastomer (TPE) and conductive thermoplastic polyurethane (TPU). Such materials may be formed by an injection-moulding, heat-pressing, heat-lamination or thermo-forming process. Alternatively, such materials may be formed by 3D printing, computer numerical control (CNC) machining/milling, laser or water jet cutting (e.g. of uniform sheets of material). Such materials may be made to be substantially rigid or pliable and/or deformable.

The first electrode and the second electrode may be formed of or comprise the same material or different materials. The first and/or second electrodes may have a uniform thickness or a non-uniform thickness. The thickness of the first electrode and the second electrode may be the same or different. The sensing point(s) may be positioned at or near a periphery or a peripheral edge of the first and/or second electrode. The sensing point(s) may be distributed around or about the periphery or peripheral edge of the first or second electrode. The sensing point(s) may be distributed evenly or unevenly around the periphery/peripheral edge of the first and/or second electrode.

The second electrode may be arranged over, under, on top of, beneath, above or below, the first electrode. The device may be configured such that the first electrode and second electrode are permanently separated from each other in some areas such that they cannot contact each other, and not in others.

The electrode (i.e. the first or the second electrode) with the sensing point(s) may be referred to as a sense electrode. The other electrode (i.e. the second or the first electrode, respectively) may be referred to as a reference or ground electrode. The reference electrode may be connected to the measurement module at one or more reference or ground points on the reference electrode. The reference electrode may be electrically grounded (e.g. by connection to ground/reference terminal of the measurement module). The first electrode and the second electrode may together form a pressure sensing layer.

Each sensing point may be selectively connectable to the measurement module by a conductive trace or track. The conductive trace/track may be or comprise a wire, a conductive thread or a printed/deposited conductive trace/track on a substrate (e.g. thin flexible substrate or PCB).

The measurement module may be or comprise a sensing circuit configured to measure changes in capacitance, e.g. at the sensing points connected to the sensing circuit. The sensing circuit may be or comprise a capacitive sensing chip with one or more sensing or input channels, such as a capacitive sensing micro-processor or micro-controller. The capacitive sensing chip may be configured to measure changes in the capacitance of the sense electrode via each sensing point connected to its input pin(s). The capacitance measurement may be based on self-capacitance of the sense electrode. The capacitance measurement may optionally be a frequency-based measurement. A change in the separation between the first and second electrode (e.g. via a change in the distance/gap(s)) affects the capacitive coupling between the first and second electrodes which in turn produces a change in the measured capacitance.

Each sensing point may be connectable to the sensing circuit at the same sensing input pin of the sensing circuit. This minimises the quantity of sensing channels needed from a capacitive sensing chip. Such capacitive sensing chips are low cost. Alternatively, two or more sensing points (or each sensing point) may be connectable to the sensing circuit at a different sensing input pin of the sensing circuit.

The measurement module may further comprise a switching unit connected between the sensing circuit and the sensing points. The switching unit may be configured to selectively connect and/or disconnect each sensing point to/from the sensing circuit. The switching unit may comprise one or more switching elements, such as transistors (e.g. general purpose, PNP and/or NPN transistors), relays and/or any other controllable switching elements known in the art. Each sensing point may be connected or connectable to the/an input pin of the sensing circuit via a switching element. The switching unit thus enables the sensing circuit to obtain measurements or readings from each sensing point individually (i.e. scan through the sensing points), all sensing points simultaneously, and/or any combination of sensing points simultaneously, by selectively connecting/disconnecting each sensing point from a (single) input pin. For example, when obtaining a measurement from an individual sensing point, the sensing circuit may be configured to connect that sensing point to the input pin and disconnect all other sensing points from the input pin(s). This may ensure the circuitry is not shorted when determining a location, area and/or amount of the applied pressure from an individual sensing point.

The measurement module may further comprise a control unit connected to the switching unit to control the connecting and/or disconnecting of each sensing point. The control unit may be configured to provide one or more control signals to the switching elements of the switching circuit to control their operation. The control unit may be configured to control the timing and/or frequency of the switching.

The measurement module may be configured to operate in a first mode and/or a second mode. In the first mode, the switching unit may scan through each sensing point (i.e. selectively connect each individual sensing point to the sensing circuit one by one), such that the sensing circuit can obtain a measurement or reading from each individual sensing point separately. In the first mode, only one sensing point is actively connected to the sensing circuit at a given time. For example, while a measurement or reading is being taken from one sensing point, other (non-active) sensing points may be disconnected from the sensing circuit. The scan or switching frequency may be sufficiently high compared to a typical movement of the body to minimise any measurement lag, e.g. such that the measurement/detection may be perceived to be in real-time. For example, the scan rate may be in the range <NUM>-<NUM>. The scan or switch rate may be slower or faster depending on the application.

In the second mode, the switching unit may connect each sensing point to the sensing circuit simultaneously, such that the sensing circuit can obtain a measurement or reading of capacitance from each sensing point simultaneously. In this way, each sensing point contributes to the measurement or reading in the second mode.

The first mode may provide information on the location, area and/or the amount of the applied pressure. The second mode may provide information on the (total) amount of applied pressure. Measurements in the second mode can be taken before or after the measurements in the first mode. The measurement module may be configured to periodically and/or continuously switch/alternate between the first and second modes of operation during operation of the device. The first and second modes may be controlled by the control unit.

For a given electrode conductivity, the measured change in capacitance at a sensing point is dependent on the change/reduction in the distance between the first and second electrodes, or the one or more gaps, due to an amount of applied pressure, the distance/proximity of the applied pressure (or location of the altered distance/gap(s)) from the sensing point, and the area over which the pressure is applied. Therefore, for a fixed location and area of applied pressure the measurement provides a value positively related to the amount of the applied pressure, for a fixed amount and area of applied pressure the measurement provides a value positively related to the distance or proximity of the location of the applied pressure from the sensing point, and for a fixed amount and location of applied pressure the measurement provides a value positively related to the area of the applied pressure. Where a pressure is applied over an area, the measurement provides information on the relative location of the boundary of the area relative to the sensing point. As such, a measurement from an individual sensing point contains information on the location, area and/or amount of applied pressure. By taking measurements from multiple individual sensing points distributed over and/or around the periphery of the sense electrode, the location, area and/or amount of applied pressure can be determined (the first mode). This information can be used to build up a pressure area profile.

A measurement obtained from all sensing points simultaneously (in the second mode) provides a value positively related to the amount of the applied pressure. This (second mode) measurement can be used in conjunction with the (first mode) measurements from individual sensing points to improve the reliability of the determined location, area and/or amount of applied pressure. For example, the (second mode) simultaneous measurement may be used to confirm whether the applied pressure corresponds to a small amount of pressure distributed over a large area, or a large amount of pressure distributed over a small area. In other words, the (second mode) simultaneous measurement can be used to infer the correct cause of the values obtained from the (first mode) individual measurements and/or find a unique solution to the location, area and amount of applied pressure.

The first mode of operation (i.e. the scanning mode) is driven by the need of taking multiple measurements on the same unitary piece of electrode to minimise engineering complexity. By scanning through multiple individual sensing points (in the first mode), a separate measurement is taken from each different peripheral location in a short (ignorable) span of time, which collectively builds up a pressure area profile and informs the amount of pressure exerted in each area without modulating the material to prevent short-circuit. This can save significant manufacturing costs compared to conventional sensing technologies comprising a plurality of discrete sensor electrodes, where each electrode is only responsible for a small local area and a considerable amount of electrode modules (i.e. sensing elements) is needed to cover a large sensing surface, such as a seat.

The device may comprise a plurality of sense electrodes that share the same reference electrode. Each sense electrode may be connected to the measurement module. Alternatively, the device may comprise a plurality of sense electrodes and a plurality of corresponding reference electrodes. In that case, each sense electrode may be connected to the sensing circuit (e.g. to the same input pin) via the switching circuit. Each reference electrode may be connected to the same reference or ground terminal on the measurement module. In either case, the measurement module may be configured to obtain a pressure area profile from each sense electrode. These may be combined to build the overall pressure area profile for the device. A plurality of sense electrodes may be used to satisfy spatial resolution and/or mechanical requirements in a product. For example, in a shoe-sole application, the device with a plurality of sense electrodes may improve the spatial resolution of the overall combined pressure area profile.

The or each portion of the device in which the first and second electrodes are spaced apart or separated by a gap may form or provide a gapped portion or region. The device may comprise one or more gapped portions or regions in which the first and second electrodes are spaced apart and/or separated by a gap. The first and second electrodes may be configured to approach and/or contact each other in each gapped portion/region in response to a pressure or force applied to or on the or each respective gapped portion/region that changes/reduces or closes the respective gap.

Each of the first electrode and the second electrode may comprise an inner surface and an outer surface. The inner surfaces of the first electrode and the second electrode may face each other. In the or each gapped portion/region, the inner surfaces of the first and second electrodes may be separated by said gap. The gap(s) may extend substantially between the inner surfaces of the first and second electrodes in the gaped portion(s). The or each gap may comprise a width and a height.

The device may further comprise one or more separating elements configured to separate the first electrode from the second electrode, e.g. by the distance. The one or more separating elements may further be configured to provide, form and/or define the one or more gaps or gapped portions/regions. The width and height of the gap(s) may be defined by the separation element(s).

The first electrode or the second electrode may be supported or suspended over/above the other by the one or more separating elements. The separating element(s) may provide one or more support portions or regions adjacent to and/or extending between the gapped region(s). The separation element(s) may be configured to maintain a separation between the first and second electrode and/or the inner surfaces of the first and second electrodes. The separation element(s) may extend between the first and second electrodes and/or may extend from either or both of the first and second electrodes. The separation element(s) may be integrally formed with the first and/or second electrode. Alternatively or additionally, the separation element(s) may be separate to/from the first and/or second electrode.

The separation element(s) may be formed of or comprise a substantially rigid/non-compressible material or a substantially flexible/compressible material. In the latter case, the gap(s) may be reduced and/or closed by a pressure applied directly over the gap(s) or gapped portion/region(s) and/or by a pressure applied over the support region(s) (i.e. not directly over the gap(s)).

In one embodiment, the or each separation element is or comprises a non-conductive separation or spacer layer. The spacer layer may be sandwiched between the first and second electrodes to separate or maintain a separation between the first and second electrodes and/or the inner surfaces of the first and second electrodes. The first electrode and/or the second electrode may be supported by the spacer layer. The spacer layer may be a unitary piece of material.

The spacer layer may comprise one or more through-holes, openings or cut-outs. The one or more through-holes, openings or cut-outs may form, define or provide the gap(s) or gapped portion/region(s). The portions or regions of the spacer layer adjacent to and/or extending between the through-holes, openings or cut-outs may define the support region(s). The spacer layer may comprise an array of such through-holes or openings. The thickness of the spacer layer may define the size/height of the gap. The width of the/each through-hole or opening may define the width of the gap or gapped portion/region. The first electrode and the second electrode may extend across the width of the or each through-hole, opening or cut-out.

The or each through-hole or opening may extend through the thickness of the spacer layer. The or each through-hole or opening may comprise a circular, square, rectangular, polygon or an arbitrary shaped cross-section. Each through-hole or opening may be the same or different shape and/or size. The through-hole(s) or opening(s) may comprise one or more holes, hollows, and/or repeating geometric patterns/tracks. Alternatively, one or more openings may extend partially through the thickness of the spacer layer. For example, one or more openings may be or comprise a recess or thickness variation of the spacer layer.

The spacer layer may comprise the conductive traces or tracks connecting each sensing point to the measurement module and/or sensing circuit.

The spacer layer may be substantially flexible, deformable and/or compressible. The spacer layer may be formed of or comprise a thermoformable non-conductive material and/or may be formed by a moulding process. Suitable materials for the spacer layer may include but are not limited to non-conductive plastics, non-conductive polymer materials and non-conductive foams, such as non-conductive acrylonitrile butadiene styrene (ABS), polyurethane (PU), polycarbonate (PC), polyvinyl chloride (PVC), ethylene vinyl acetate (EVA), thermoplastic elastomer (TPE), thermoplastic polyurethane (TPU) and silicone rubber. Such materials may be made to be substantially rigid or pliable and/or deformable and may undergo an injection-moulding, heat-pressing, heat-lamination or thermo-forming process. Alternatively, such materials may be formed by 3D printing, computer numerical control (CNC) machining/milling, laser or water jet cutting (e.g. of uniform sheets of material). Alternatively, the spacer layer may be formed from or comprise a fabric, paper or latex. The spacer layer may have a similar or higher elasticity and/or flexibility to the first and second electrodes.

In some cases it may be advantageous to eliminate the need for a separate separation/spacer layer (made of a different material) to further minimise assembly cost and complexity. The spacer layer may be integral with the first and/or second electrode. The first and/or second electrode being mouldable allows them to be formed into customisable 3D structures where natural overhangs and/or projections can be formed and used as integral spacers.

For example, in an alternative embodiment, the one or more separation elements may be or comprise one or more projections extending from (an inner surface of) the first and/or second electrodes. The one or more separation elements may be or comprise an array of such projections. The projection(s) may be configured to serve as spacers. The spacer(s) may be configured to maintain the first and second electrodes in the spaced apart relationship. The spacer(s) may be integrally formed with the first and/or second electrode to form a monolithic structure. The spacers may have a proximal end attached to the inner surface of the respective one of the first or second electrode and a distal end.

The gap(s) or gapped portion/region(s) may be formed, provided or defined between the spacer(s) and/or in the region(s) adjacent to the spacer(s). The one or more gaps (of the or each gapped portion) or the or each gapped portion/region may extend substantially in the region around, either side of and/or between the one or more projections/spacers. In other words, the gap(s) or the gapped portion(s) may be defined either side of and/or between the one or more projections/spacers.

The spacer(s) may extend away from the inner surface of the first and/or second electrode to a distance defined by their length. The size/height of the gap (i.e. in the thickness direction) may be determined at least in part by the length of the or each projection/spacer. The width of the gap(s) may be determined by the geometry/design of the projection(s)/spacer(s), e.g. the separation between adjacent projections/spacers.

The spacers may be formed of or comprise the same or different material to the first and/or second electrode. The spacers may have the same or different electrical, thermal and/or mechanical properties as the first and/or second electrode. This can be achieved by forming the spacers in the same (single) moulding step as the first and/or second electrode, or by using a two-step over-moulding process.

The distal end of the or each spacer may contact (the inner surface of) the other of the first and second electrode. In this case, the spacer(s) may support the respective one or the first and second electrodes against the other of the first and second electrodes, or the other of the first and second electrodes may be supported by the spacer(s) (depending on the orientation of the device). Either or both of the first and second electrodes may comprise one or more projections to serve as spacers.

Alternatively, the spacer(s) may not contact the other of the first and second electrode. In one embodiment, the other of the first and second electrode may comprise one or more corresponding through-holes, openings or cut-outs configured to receive a portion of the spacer(s), such that the spacer(s) do not contact the other of the first and second electrode. In another embodiment, the first and second electrodes may be dimensioned such that the spacers are located outside the periphery of the other of the first and second electrodes, such that the spacer(s) do not contact the other of the first and second electrode.

The length of the spacer(s) (or distance to which the spacer(s) extend away from the inner surface of the first/second electrode) may be greater than the depth of the through-hole(s) or opening(s) (or thickness of the electrode comprising the through-hole(s) or opening(s)). In this way, the electrode comprising the spacer(s) is separated from the electrode comprising the through-hole(s) or opening(s) in the thickness direction by the gap (where the length of the spacer(s) is in the same direction of the holes). The spacer(s) may be configured to fit within the through-hole(s) or opening(s) without contacting the sides of the through-hole(s) or opening(s). The size/height of the gap (i.e. in the thickness direction) may further be determined at least in part by the depth of the through-hole(s) or opening(s), or the thickness of the electrode comprising the through-hole(s) or opening(s).

The spacer(s) may be configured to minimise the foot-print of the distal end. In this way, where the distal end contacts the other of the first and second electrode, the electrical contact between the two electrodes is minimised such that the capacitance measurement is not compromised. The spacer(s) may comprise a sidewall connecting the proximal and distal ends. The sidewall may extend in a direction substantially perpendicular to the inner surface of the respective one of the first and second electrode. Alternatively, the sidewall may be angled with respect to the inner surface of the respective one of the first and second electrode, such that spacer(s) is/are substantially pointed and/or the distal end of the spacer(s) has/have a smaller foot-print or cross-sectional area than the proximal end. This may reduce the foot-print of the distal end. In addition, where the spacer(s) is/are angled, the footprint or contact area between the distal end and the other of the first and second electrodes may increase with an applied pressure due to compression of the spacer(s) and/or electrodes. This may provide a change in capacitance that adds to/combines with the change resulting from the reduced gap to enhance the overall magnitude of the measured change in capacitance.

The projection(s) or spacer(s) may be formed of or comprise the same material as the first and/or second electrode comprising the projection(s)/spacer(s). The projection(s) may be integrally formed with the first and/or second electrode comprising the projection(s), e.g. formed in the same moulding step.

Alternatively, the projection(s)/spacer(s) may be formed of or comprise a different material and/or have different material properties (e.g. electrical conductivity and/or mechanical properties) to the material of the first and/or second electrode comprising the projection(s)/spacer(s). In this way, the projection(s)/spacer(s) may have a different rigidity to the rest of the first and/or second electrode comprising the projection(s). For example, the projection(s)/spacer(s) may be formed in a different moulding step.

The projection(s)/spacer(s) may be substantially rigid, such that the projection(s)/spacer(s) maintain a fixed separation between the first and second electrodes at or near to the projection(s)/spacer(s) upon application of a pressure or force. In another example, the projection(s)/spacer(s) may be substantially deformable and/or resilient, such that the projection(s)/spacer(s) are compressible upon application of a pressure or force to provide a changeable separation/gap between the first and second electrodes at or near to the projection(s)/spacer(s).

The pressure or force required to change/reduce and/or close the gap(s) may be partially determined by the flexibility/deformability of the first, second electrode and/or the separation element(s), and partially determined by the dimensions (i.e. width and height) of the gap(s) or gapped portion/region(s). As such, the thickness of the spacer layer and the width of the or each through-hole or opening may be configured to set a predetermined pressure or force required to reduce/change or close the gap (of the or each respective gapped portion/region). Alternatively, the length of the or each projection/spacer and the width of the region either side of and/or between the one or more projections/spacers may be configured to set a predetermined pressure or force required to close the or each gap (of the or each respective gapped portion/region). This may be used to tune or tailor the pressure-sensitivity of the device in addition of instead of tuning the flexibility/deformability of the first and/or second electrode.

The first electrode and/or the second electrode may have an electrical resistivity in the range of substantially <NUM>×<NUM><NUM>-<NUM>×<NUM><NUM> Ohm. The resistance between any two points on the first electrode and/or the second electrode may be between substantially <NUM> kOhm and <NUM> MOhm measured over a distance of about <NUM>. Having a large resistivity means that the magnitude of the measured change in capacitance varies more strongly with the distance between the location of the applied pressure on the device and an individual sensing point, thus increasing the pressure sensitivity of the device and/or the position sensing resolution.

The resistivity and/or resistance of the first electrode and/or the second electrode may be tuned via the intrinsic material properties (i.e. intrinsic resistivity). Alternatively or additionally, the resistivity and/or resistance of the first electrode and/or the second electrode may be tuned without changing the intrinsic material properties by introducing instead one or more holes, hollows, recesses, thickness variations, and/or repeating geometric patterns/tracks into the first electrode and/or the second electrode. For example, the first electrode and/or the second electrode may be or comprise a complex shape and/or a repeating geometric pattern to provide a predetermined resistance between any two given points. There may be a plurality of hollows and/or recesses forming a regular array. The one or more holes, hollows and/or recesses may define a non-linear conduction path between the two points. Alternatively or additionally, the one or more hollows and/or recesses may define a plurality of linear and/or non-linear conduction paths between the two points.

The first electrode and the second electrode may be exchanged. For example, the second electrode may instead comprise the one or more sensing points connectable to the measurement module and/or sensing circuit.

According to a second aspect of the invention, there is provided a method of manufacturing the pressure sensing device of first aspect, as defined in claim <NUM>. The method may comprise forming the first electrode and the second electrode. The first electrode and the second electrode is formed of or comprises a unitary piece of non-metallic conductive material. The first electrode and/or the second electrode may be formed of or comprise a moveable and/or deformable and/or flexible non-metallic conductive material. The method further comprises arranging the first and second electrodes in a spaced apart configuration, such that the first and second electrodes are separated by a distance. The method may further comprise providing the measurement module. The method further comprises connecting the measurement module to one of the first or second electrodes at one or more sensing points or a plurality of sensing points on said electrode. The one or more sensing points may be distributed around the periphery or peripheral edge of the first or second electrode (evenly or unevenly). The method may further comprise connecting the measurement module to the other of the first or second electrodes at one or more reference or ground points on the other of the first or second electrode.

The method may further comprise spacing the first electrode from the second electrode, or vice versa, in a stacked arrangement. For example, the method may further comprise arranging the second electrode over, under, on top of, beneath, above or below the first electrode such that the second electrode is separated from the first electrode by a distance, and optionally such that there are one or more gapped portions/regions in which the first and second electrodes are separated by a gap. The first and second electrodes may be substantially planarly aligned.

The electrode (i.e. the first or second electrode) with the sensing point(s) may be referred to as a sense electrode. The other electrode (i.e. the second or first electrode, respectively) may be referred to as a reference or ground electrode.

The method may further comprise forming a plurality of sense electrodes and arranging the plurality of sense electrodes over, under, on top of, beneath, above or below the same reference electrode. The method may further comprise connecting the measurement module to each of the sense electrodes at the sensing point(s) on the respective sense electrode.

The method may further comprise forming a plurality of sense electrodes and a plurality of corresponding reference electrodes, and arranging each sense electrode with respect to the corresponding reference electrode, e.g. over, under, on top of, beneath, above or below the corresponding reference electrode (e.g. so that they are planarly aligned). The method may further comprise connecting the measurement module to each of the sense electrodes at the sensing point(s) on the respective sense electrode, and optionally connecting the measurement module to each of the reference electrodes at one or more reference or ground points on each of the reference electrodes.

Forming the first and/or second electrode may comprise a thermoforming and/or a moulding process. One mould may be used for moulding multiple sub-divisions of either electrode.

The method may further comprise forming one or more separation elements configured to separate the first and second electrode. The one or more separation elements may further be configured to provide or form the gap(s). Forming the one or more separation elements may comprise a thermoforming and/or a moulding process.

Forming the one or more separation elements may comprise forming a non-conductive separation or spacer layer. The spacer layer may be substantially flexible or rigid. The method may further comprise arranging the spacer layer between the first electrode and the second electrode to separate the first and second electrodes.

Forming the first and second electrode and/or the separation/spacer layer may comprise an injection-moulding, heat-pressing, heat-lamination and/or thermo-forming process. Such fabrication processes are inexpensive. Alternatively, forming the first and second electrode and/or the separation layer may comprise 3D printing, computer numerical control (CNC) machining/milling, laser or water jet cutting (e.g. of uniform sheets of material). The method of forming each electrode may comprise forming the first and/or second electrode together in attachment to a non-conductive surface and/or object (e.g. overmoulding the first and/or second electrode onto a piece of fabric on one side). In this arrangement, one mould is needed for moulding multiple sub-divisions of either electrode.

Forming the separation/spacer layer may further comprise forming one or more through-holes, openings or cut-outs in the spacer layer to provide the gap of the or each respective gapped portion. Forming the spacer layer may further comprise forming an array of through-holes in the spacer layer.

In another embodiment, forming the first and/or second electrode may comprise forming one or more projections extending from (a surface of) the first and/or second electrodes. Forming one or more projections may comprise forming an array of such projections. The projection(s) may be configured to serve as spacers. The spacer(s) may be configured to maintain the first and second electrodes in the spaced apart relationship. The spacer(s) may be integrally formed with the first and/or second electrode to form a monolithic structure (e.g. formed in the same moulding step). Forming the spacer(s) may comprise forming spacer(s) with a sidewall extending in a direction substantially perpendicular to the surface of the respective one of the first and second electrode. Alternatively, forming the spacer(s) may comprise forming spacer(s) with a sidewall substantially angled with respect to the surface of the respective one of the first and second electrode, such that the spacer(s) is/are substantially pointed and/or the distal end of the spacer(s) has/have a smaller foot-print or cross-sectional area than the proximal end.

Forming the first and second electrode may further comprise forming one or more through-holes, openings or cut-outs in one of the first and second electrodes configured to receive a portion of the or each projection/spacer, such that the spacer(s) do not contact the other of the first and second electrode when the first and second electrodes are arranged in the spaced apart configuration.

Optionally or preferably, forming the first and second electrode may comprise forming an array of said through-holes, openings or cut-outs in the one of the first and second electrode to receive the corresponding array of said projections/spacers in the other of the other of the first and second electrodes.

According to a third aspect of the invention, there is provided a method of operating the pressure sensing device of the first aspect as defined in claim <NUM>. Determining the area may comprise determining the shape of the applied pressure. The method may further comprise determining a pressure area profile from the determined area, location and/or amount of the applied pressure.

The change of capacitance may be measured at a measurement module. Measuring a change of capacitance at each sensing point individually may comprise scanning through each sensing point sequentially. Scanning may comprise selectively connecting and disconnecting each sensing point to/from the measurement module, such that only one sensing point or any combination of sensing points is connected to the measurement module at any given time. This may ensure the circuitry is not shorted when determining a location, area and/or amount of the applied pressure from an individual sensing point.

For example, while a measurement or reading is being taken from one sensing point, other (non-active) sensing points may be disconnected from the sensing circuit. The scan frequency may be sufficiently high compared to a typical movement of the body to minimise any measurement lag, e.g. such that the measurement/detection may be perceived to be in real-time. For example, the scan rate may be in the range <NUM>-<NUM>. The scan rate may be slower or faster depending on the application.

By scanning through multiple individual sensing points, a separate measurement/reading is taken from each different location in a short (ignorable) span of time, which collectively builds up a pressure area profile and informs the amount of pressure exerted in an area without modulating the material to prevent short-circuit. This can save significant manufacturing costs compared to conventional sensing technologies comprising a plurality of discrete sensor electrodes, where each electrode is only responsible for a small local area and a considerable amount of electrode modules (i.e. sensing elements) is needed to cover a large sensing surface, such as a seat.

Measuring a change of capacitance at each sensing point simultaneously may comprise connecting each sensing point to the measurement module.

Measuring a change may comprise measuring, at a measurement module using a single input pin of a capacitive sensing chip.

According to a fourth aspect of the invention, there is provided a shoe insole comprising one or more pressure sensing devices according to the first.

According to a fifth aspect of the invention, there is provided a seat for an automobile or aircraft comprising one or more pressure determining devices according to the first aspect.

According to a sixth aspect of the invention, there is provided a consumer product comprising one or more pressure sensing devices according to the first. The consumer product may be or comprise a phone case, laptop, or a surface of a wall, table or object, wherein the one or more pressure sensing devices are configured to provide one more trackpads. The consumer product may be connectable to a computing device to provide a user interface to control one or more functions of the computing device based on the determined location, area and/or amount of pressure applied to the one or more sensing devices.

In order that the invention can be well understood, embodiments will now be discussed by way of example only with reference to the accompanying drawings, in which:.

It should be noted that the figures are diagrammatic and may not be drawn to scale. Relative dimensions and proportions of parts of these figures may have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar features in modified and/or different embodiments.

<FIG> (top panel) shows a schematic diagram of a pressure sensing device <NUM> according to an embodiment of the invention. The device <NUM> comprises a pressure sensing layer <NUM> connected to a measurement module <NUM> at a plurality of sensing points S1, S2 located at or near the periphery of the sensing layer <NUM>. The sensing layer <NUM> is configured to provide a change in an electrical signal (capacitance) in response to a pressure or force applied on or to (either side of ) the sensing layer <NUM>, as will be discussed in more detail below with reference to <FIG>. The measurement module <NUM> is configured to measure the electrical signal(s) and determine the location, area and amount of applied pressure on the sensing layer <NUM> based on the measured electrical signal(s).

The measurement module <NUM> comprises a sensing circuit <NUM> configured to measure the pressure-induced changes in capacitance at the sensing points S1, S2. In an embodiment, the sensing circuit <NUM> is a capacitive sensing chip with one or more sensing/input channels or pins <NUM>, such as a capacitive sensing micro-processor or micro-controller. The sensing circuit <NUM> is connected to the sensing points S1, S2 via a switching unit <NUM> (an example of which is shown in more detail in the bottom panel of <FIG>). The switching unit <NUM> is configured to selectively connect and disconnect the sensing points S1, S2 to/from the sensing circuit <NUM>. The switching circuit <NUM> comprises a plurality of switching elements SW1, SW2, such as transistors (e.g. general purpose, PNP and/or NPN transistors), relays and/or any other controllable switching elements known in the art. In the embodiment shown in <FIG>, each sensing point S1, S2 is connected to the same input pin <NUM> of the sensing circuit <NUM> via the switching elements SW1, SW2. The switching unit <NUM> thus enables the sensing circuit <NUM> to obtain measurements or readings from each sensing point S1, S2 individually, all sensing points S1, S2 simultaneously, and/or any combination of sensing points S1, S2 using only a single input pin <NUM> by selectively connecting/disconnecting each sensing point S1, S2. Alternatively, each sensing point S1, S2 may be connected to a different input pin <NUM> of the sensing circuit <NUM>, as shown in <FIG>. The measurement configurations will be described in more detail below with reference to <FIG> and <FIG>.

Each sensing point S1, S2 is connected to the measurement module <NUM> via a conductive trace <NUM>. For example, the conductive trace <NUM> may be or comprise a wire, conductive thread, or conductive track on a substrate or printed circuit board (or a separate spacer layer, see <FIG>), which may be flexible (not shown). Although only connections to the input pins(s) <NUM> are shown in <FIG>, there may be additional connections between the sensing layer <NUM> and the sensing circuit <NUM> required for the measurements (not shown). For example, one or more portions of the sensing layer <NUM> may be connected to a ground or reference pin of the sensing circuit <NUM> via a conductive trace <NUM> (see below).

The measurement module <NUM> further comprises a control unit <NUM> connected to the switching unit <NUM> to control the switching elements SW1, SW2 and thus control the connections between the sensing points S1, S2 and the sensing circuit <NUM>. The control unit <NUM> may be or comprise a microcontroller or a microprocessor chip. The control unit <NUM> comprises multiple input/output (I/O) channels <NUM> connected to the respective control inputs/terminals of the switching elements SW1, SW2 that provide output signals configured to control the timing and frequency of the switching of each switching element SW1, SW2. The timing and frequency of the switching may be controlled by a software program running on the control unit <NUM> or another computing device in communication with the control unit <NUM>. Example configurations of the controllable switching elements SW1, SW2 are shown in the bottom panels of <FIG> for the case of transistors. It will be appreciated that the above switching operation may be achieved in other ways and/or using other active or passive switching components.

The control unit <NUM> is further configured to receive measurement data from the sensing circuit <NUM> (e.g. via an I/O channel <NUM>) for determining the location, area and amount of applied pressure. Calculations of the location, area and amount of applied pressure can be performed on-chip using suitable software running on the control unit <NUM>. The control unit <NUM> may be configured to store, process and/or analyse the data. Alternatively or additionally, the control unit <NUM> may be in communication with a remote computing device running software configured to receive, process, store and/or analyse the measurement data from the control unit <NUM> (not shown). For example, the computing device may be configured to visualise the data obtained from the device <NUM>. The computing device may comprise a user interface configured to visualise the data and control the device <NUM>. Determination of the location, area and amount of pressure will be discussed in more detail below with reference to <FIG>.

The sensing layer <NUM> is configured to provide pressure-induced changes in capacitance through deformation of the sensing layer <NUM> that can be measured by the sensing circuit <NUM> at the sensing points S1, S2. Alternatively, This allows the sensing circuit <NUM> to be or comprise a commercially available capacitive sensing microprocessor (CSM) or microcontroller. Such CSMs are generally cheaper and require fewer sensing input pins <NUM> compared to pressure sensing microprocessors or load cells. In the embodiment of <FIG> where each sensing point S1, S2 is connected to the same input pin <NUM>, the lower number of input pins in use allows the use of cheaper alternative CSMs (e.g. with few-channels), rather than multi-channel CSMs with a higher number of pins (e.g. <NUM> channels vs <NUM> channels).

<FIG> shows a cross-sectional view of a generalised pressure sensing layer <NUM> to illustrate the general form and operating principle of the device <NUM>. The sensing layer <NUM> comprises a first electrode <NUM> and a second electrode <NUM> spaced apart from the first electrode <NUM> in the thickness direction Z, such that the electrodes <NUM>, <NUM> are separated from each other by a distance d. In other words, the two electrodes <NUM>, <NUM> are arranged in a stacked configuration, one over the other. Although the second electrode <NUM> is shown arranged over the first electrode <NUM>, the order of the two electrodes <NUM>, <NUM> can be exchanged. For example, the second electrode <NUM> may instead be arranged beneath/below the first electrode <NUM>.

The first electrode <NUM> and/or the second electrode <NUM> is formed of or comprises a moveable and/or deformable and/or flexible material. One or each of the first electrode <NUM> and the second electrode <NUM> may be moveable with respect to each other, or the first electrode <NUM> and/or the second electrode <NUM> may deform and/or flex, to reduce/change the distance d between the electrodes <NUM>, <NUM> (uniformly or non-uniformly) in one or more locations in response to a pressure or force applied to or on either electrode <NUM>, <NUM> (i.e. from either or both sides of the sensing layer <NUM>). This is illustrated in <FIG> which shows the second electrode <NUM> in a substantially un-deformed/un-flexed position (i) in the absence of a pressure/force, and a substantially deformed/flexed position (ii) in the presence of a pressure or force applied to the second electrode <NUM> from the second electrode <NUM> side of the sensing layer <NUM> that decreases the distance d, as indicated by the arrow. Therefore, at least the electrode to which a pressure or force is to be applied is substantially deformable and/or flexible, or capable of flexing, in order for the device <NUM> to operate. The other electrode may be substantially rigid or deformable/flexible, depending on the application. For example, if the entire sensing layer <NUM> is required to be flexible, then both electrodes <NUM>, <NUM> can be deformable/flexible.

The capacitance of the first electrode <NUM> is influenced by the proximity to or distance from the second electrode <NUM>, and vice versa. As such, a change/reduction in the distance d in response to a pressure or force applied on or to the sensing layer <NUM> results in a change in capacitance between the first and second electrodes <NUM>, <NUM> that can be measured by the sensing circuit <NUM> at the sensing points S1, S2. This is the basis of the operating principle of the device <NUM>, which will be described in more detail below. Further, the operation of the device <NUM> does not rely on any capacitive coupling of the electrodes <NUM>, <NUM> with the object or body providing the pressure/force.

The sensing points S1, S2 can be located on either the first electrode <NUM> or the second electrode <NUM>. The electrode with the sensing points S1, S2 is the sense electrode. The other electrode is a reference electrode connected at one or more reference points to a ground or reference pin of the sensing circuit <NUM> (not shown).

The distance d or space between the electrodes <NUM>, <NUM> may be substantially empty, such that the electrodes <NUM>, <NUM> are separated from each other by a gap, such as an air gap or void. Alternatively, the space between the electrodes <NUM>, <NUM> can be at least partially filled or occupied by a non-conductive spacer layer or spacer material that is substantially compressible and resilient to permit the distance d between the electrodes <NUM>, <NUM> to change under an applied pressure/force (not shown). For example, the spacer layer/material may be formed of or comprise ABS, EVA, PU, rubber or a foam.

<FIG> shows an example of a sensing layer <NUM> in which the electrodes <NUM>, <NUM> are separated from each other by a gap. In this embodiment, the sensing layer <NUM> comprises one or more gapped portions <NUM> in which the first and second electrodes <NUM>, <NUM> are separated by the gap. Outside the gapped portion(s) <NUM> are one or more support portions <NUM> in which first and second electrodes <NUM>, <NUM> are separated by one or more separation elements (not shown). The separation element(s) are configured to maintain a separation between the first and second electrodes <NUM>, <NUM> and provide or form the gap(s). As such, the separation element(s) support the overall structure of the sensing layer <NUM>. The separation element(s) may be separate from or integral with the first and/or second electrodes <NUM>. <NUM>, as shown in <FIG> and <FIG> and described below.

The first electrode <NUM> and the second electrode <NUM> are formed of or comprise a unitary piece of non-metallic conductive material, such as a conductive plastic or a polymer (e.g. conductive acrylonitrile butadiene styrene (ABS), conductive ethylene vinyl acetate (EVA), or conductive polyurethane (PU)). Such materials are thermoformable and can therefore be formed using known moulding processes, such as injection moulding, heat pressing or any other thermoforming process. This significantly increases the design freedom for the electrode shape and the device <NUM> itself.

In an embodiment, the electrical resistivity of the sense electrode (i.e. the first or second electrode <NUM>, <NUM>) is in the range of substantially <NUM>×<NUM><NUM>-<NUM>×<NUM><NUM> Ohm. This means that the resistance between any two points on the sense electrode measured over a distance of about <NUM> is between substantially <NUM> kOhm and <NUM> MOhm. The reference electrode (i.e. the other of the first or second electrode <NUM>, <NUM>) may have the same or different resistivity to the sense electrode. For example, the reference electrode may have a substantially lower resistivity than the sense electrode.

<FIG> shows an embodiment of a sensing layer <NUM> in which the separation element(s) is or comprises a non-conductive separation or spacer layer <NUM> positioned between the first and second electrodes <NUM>, <NUM>. The spacer layer <NUM> comprises one or more openings <NUM> that form/provide the gap(s), and thus form the gapped portion(s) <NUM> and the support portion(s) <NUM>. The width W of the gap(s) or gapped portion(s) <NUM> is defined by the size and shape of the opening <NUM>. As such, the spacer layer <NUM> separates and also electrically isolates the first and second electrodes <NUM>, <NUM> in the support portions <NUM>.

The spacer layer <NUM> can be formed of or comprise a non-conductive plastic or polymer material (e.g. ABS, EVA, or PU), or any other thermoformable non-conductive material. In this way, the spacer layer <NUM> can also be formed using a moulding process. Alternatively, the spacer layer <NUM> can be formed of or comprise a fabric or a fibrous material, such as paper. Where the spacer layer <NUM> is formed of or comprises a thermoformable non-conductive material and is produced by a moulding process, the opening(s) <NUM> may be formed by the same moulding process. Alternatively, the opening(s) <NUM> may be formed by selectively cutting or removing material from a uniform sheet forming the spacer layer <NUM>.

The spacer layer <NUM> may be substantially rigid or deformable/flexible, depending on the application. For example, if the entire sensing layer <NUM> is required to be flexible, then both the first and second electrodes <NUM>, <NUM> and the spacer layer <NUM> can be formed of or comprise deformable/flexible materials. Where the spacer layer <NUM> is flexible/deformable it may be able to compress under an applied pressure thus changing the gap between the first and second electrodes <NUM>, <NUM>. In this case, the sensing layer <NUM> may be responsive to pressure applied to or on the support portions <NUM> as well as the gapped portions <NUM>.

Although the sensing layer <NUM> is shown as a tri-layer structure, it will be appreciated that the sensing layer <NUM> may comprise additional conductive/non-conductive layers without altering the operating principle of the device <NUM>. For example, the spacer layer <NUM> itself may formed as a multi-layer structure.

<FIG> show alternative embodiments of a sensing layer <NUM> in which the first and second electrodes <NUM>, <NUM> are separated and the gap is formed without using a separate spacer layer <NUM>. In this embodiment, the separation element(s) is or comprises one or more projections <NUM> that extend from an inner surface 20i of the second electrode <NUM> to server as spacers (although it will be appreciated that either or both electrodes <NUM>, <NUM> may comprise such projection(s)). The spacer(s) <NUM> of the sensing layer <NUM> are integrally formed with the first and/or second electrode <NUM>, <NUM> thus forming a monolithic structure (e.g. formed during the same moulding process). In this embodiment, the width W of the gap or gapped portion(s) <NUM> is defined by the region between adjacent spacers <NUM> and/or the region surrounding a spacer <NUM>.

In the embodiment of <FIG>, the spacers <NUM> are located beyond the periphery of the first electrode <NUM> and extend to a (non-conductive) support surface S, such that they do not contact the first electrode <NUM>. In the embodiment of <FIG>, the spacers <NUM> extend through one or more openings <NUM> in the first electrode <NUM> to the support surface S, such that they do not contact the first electrode <NUM> (i.e. the spacers <NUM> fit within the opening(s) <NUM> such that they do not contact the sides of the openings <NUM>). In both examples, the spacer(s) <NUM> extend in the thickness direction of the sensing layer <NUM> (i.e. the Z- direction) to a length that is greater than the thickness of the first electrode <NUM>. This ensures that, when the first electrode <NUM> is placed against a surface S, the spacer(s) <NUM> supports the second electrode <NUM> against the surface S at a spaced apart relationship to the first electrode <NUM> and forms/provides the gap, as shown. Further, as the spacers <NUM> do not contact the first electrode <NUM>, the first and second electrodes are electrically isolated.

Where the electrode comprising the spacers <NUM> is deformable, the spacers <NUM> are able to compress under an applied pressure, thus changing the gap between the first and second electrodes <NUM>, <NUM>. In this case, the sensing layer <NUM> may be responsive to pressure applied to or on the support portions <NUM> as well as the gapped portions <NUM>.

In an alternative configuration shown in <FIG>, the spacers <NUM> supporting the electrode <NUM> may rest directly on the surface 10i of the first electrode <NUM>. Due to the relatively high resistivity of the electrodes <NUM>, <NUM>, substantial shorting of the electrodes is avoided and the capacitance measurement is not compromised. In this case, the spacers <NUM> may be configured to minimise the contact area between the distal end of the spacer <NUM> and the first electrode <NUM>. For example, the spacers <NUM> may be substantially convex or pointed, as shown in <FIG>. In this way, when pressure is applied to the sensing layer <NUM>, the contact area between the spacer <NUM> and the first electrode <NUM> can increase due to the deformable nature of the first and/or second electrode <NUM>, <NUM> material, thus producing a change in the measured capacitance, in addition to that produced from a change in the gap alone. The sensing layer <NUM> may therefore be responsive to pressure applied to or on the support portions <NUM> as well as the gapped portions <NUM>.

As the spacers <NUM> are integrally formed with the first and/or second electrode <NUM>, <NUM>, manufacture and assembly of the sensing layer <NUM> may be simplified compared to the sensing layer <NUM> requiring a separate spacer layer <NUM>. The spacers <NUM> may be formed of or comprise the same material as the first and/or second electrode <NUM>, <NUM> and therefore have the same electrical and/or mechanical properties as the first and/or second electrode <NUM>, <NUM>. Alternatively, the spacers(s) <NUM> can be formed of or comprise a different material and/or have different electrical and/or mechanical properties to the first and/or second electrode <NUM>, <NUM>, e.g. by using a two-step over-moulding process (as indicated by the dotted lines in <FIG>). In this way, the spacer(s) <NUM> may be formed of or comprise a non-conductive material, e.g. to ensure the electrodes <NUM>, <NUM> remain electrically isolated even when the spacers <NUM> rest directly on the inner surface 10i of the first electrode <NUM> as seen in <FIG>.

Due to the absence of a spacer layer <NUM>, the sensing layer <NUM> may be suited to scaling down to small sizes, since the size and geometry of the integral spacer(s) <NUM> and/or opening(s) <NUM> can be controlled more accurately during the moulding process. For example, features sizes down to <NUM> with a <NUM> tolerance can be achieved using injection moulding, allowing small pressure sensing devices, e.g. with XYZ dimensions as small as <NUM>-<NUM>, with specific shapes/contours to be produced, and easily integrated with a small product/object. By contrast, it is difficult to fit off-the-shelf electronic pressure sensors or load cells into small product/objects.

The device <NUM> is responsive to applied pressures that reduce the gap as well as applied pressures that close the gap. The pressure-sensitivity of the sensing layers <NUM>, <NUM>, <NUM> is determined by how easily the electrode to which the pressure is applied can deform and flex to reduce and eventually close the gap. This is determined by the rigidity/flexibility of the first and/or second electrode <NUM>, <NUM> and the geometry of the gap or gapped portions <NUM>, i.e. the height and width W of the gap. For example, the larger the width W of the gap the easier it is to deform and flex the first and/or second electrode <NUM>, <NUM>. Also, the smaller the height of the gap the less pressure/force is required to close the gap. As discussed above, the geometry of the gap or gapped portions <NUM> is predominantly determined by the separation elements, i.e. thickness spacer layer <NUM> and size/shape of the openings <NUM> (for sensing layer <NUM>) or the length and arrangement of the spacers <NUM> (for sensing layer <NUM>). Further, it will be appreciated that flexibility/rigidity of the electrodes <NUM>, <NUM> of the sensing layer <NUM>, <NUM>, <NUM> is itself determined by the electrode material's (intrinsic) mechanical properties and its geometry, such as the thickness of the first and/or second electrode <NUM>, <NUM>. Due to the mouldable materials used, the geometry of the electrodes <NUM>, <NUM> and the gap can be readily tuned through design to tailor the flexibility and therefore the pressure sensitivity of the device <NUM> to meet the needs of a particular application. For example, the inner surface 10i, 20i of either electrode <NUM>, <NUM> may comprise one or more recesses, ridges and/or undulations 20r to enhance the flexibility, as shown in in <FIG>.

In addition, the size of the signal measured by the sensing circuit <NUM> for a given applied pressure profile (the responsivity) is linked to the total area of deformation. This is linked to the dimensions of individual gapped portions <NUM>, but also to the fill factor of the sensing layer <NUM>, <NUM>, <NUM>, i.e. the ratio of the total area of the sensing layer <NUM>, <NUM>, <NUM> occupied by the gapped portion(s) <NUM> to the total area of the sensing layer <NUM>, <NUM>, <NUM>. The fill factor can be controlled independently from the dimensions of the individual gapped portions <NUM>, e.g. through the number and density of openings <NUM> or spacers <NUM>. As such, multiple design variables can be adjusted to tune to the device sensitivity according to the application.

<FIG> show an embodiment of the sensing layer <NUM> in which the spacer layer <NUM> comprises an array of openings <NUM>. Each opening <NUM> forms and/or provides a separate gapped portion <NUM>. As such, a pressure or force applied to the sensing layer <NUM> will change the gap in one or more gapped portions <NUM> that can be detected as a change in capacitance by the sensing circuit <NUM> (not shown). In this example, the sensing layer <NUM> comprises four sensing points S1, S2, S3, S4 on the second electrode <NUM>. The first electrode <NUM> is connected to ground. Alternatively, the sensing points S1, S2, S3, S4 can be located on the first electrode <NUM> and the second electrode <NUM> can be connected to ground. The plurality of openings <NUM> may be substantially the same size and shape, as shown, or may be different sizes and shapes (not shown). In addition, the openings <NUM> may form a regular array as shown (e.g. a repeating geometric pattern), or may form an irregular pattern (not shown). One or more openings <NUM> may form an elongate straight or curved line or wave pattern (not shown).

<FIG> show an embodiment of the device <NUM> with a sensing layer <NUM> configured as a pressure sensing shoe insole. The insole device <NUM> comprises a plurality of first electrodes 10a-10f, a single unitary spacer layer <NUM> and a single unitary second electrode <NUM>. Each first electrode 10a-f is a sense electrode comprising a plurality of sensing points S1-S12 distributed around their peripheries for connecting to the measurement module <NUM> via the traces <NUM>. The second electrode <NUM> is the reference electrode for connecting to the ground/reference pin of the measurement module <NUM>. In this way, the single unitary reference electrode serves as the reference electrode for each separate sense electrode, simplifying assembly and manufacture. In this example, the first electrodes 10a-f forming the sense electrodes are beneath the reference electrode. This allows the sense electrodes to conform to a (typically flat) shoe sole, while the reference electrode can be formed/moulded into the 3D shape of a typical insole, as shown in <FIG>. This arrangement also allows the grounded reference to shield the sense electrodes from any parasitic external capacitance, e.g. originating the user's foot. The upper side of the second electrode <NUM> may be coated or covered with a non-conductive material to provide (electrical and physical) protection and/or water resistance, e.g. the covering/coating may be a waterproof fabric.

The first electrodes 10a-f are arranged according to typical pressure zones of a foot. Partitioning/dividing the sense electrodes in this way may provide improved spatial resolution of the pressure sensing. The spacer layer <NUM> comprises a plurality of openings <NUM> also arranged in zones, each zone corresponding to one of the first electrodes 10a-f. Similarly, in this example the single unitary spacer layer <NUM> serves as the spacer layer <NUM> for each first electrode 10a-f, simplifying assembly and manufacture. Alternatively, it will be appreciated that the (second) reference electrode and/or spacer layer <NUM> can be partitioned/divided into a plurality of separate spacer layers <NUM> to match the separate sense electrodes.

The conductive traces <NUM> are formed in or on a flexible substrate (e.g. a flexible PCB) that extends around the periphery of sensing layer <NUM>, which in this case corresponds to the periphery of the shoe sole. Arranging the traces <NUM> in this way may increase the robustness of the insole device <NUM>, by reducing the direct pressure or forces exerted on the traces <NUM> by the foot and the associated wear and tear.

Each opening <NUM> provides a gapped portion <NUM> that is responsive to an applied pressure or force and contributes to the measured changes in capacitance at the sensing points. By scanning through each sensing point S1-S12 on each sensing layer 10a-10f, multiple forced locations/areas can be determined and a pressure area map can be built up. <FIG> shows an example pressure area map that may be obtained from the insole device <NUM> of <FIG> when worn by a user. Each circle represents a XY location on the map, and the radius of each circle represents the magnitude of the determined pressure or force at that location.

<FIG> show an alternative embodiment of an insole device <NUM> with sensing layer <NUM> in which the first electrode <NUM> is a single unitary sense electrode and the traces <NUM> are incorporated into the spacer layer <NUM>. The traces <NUM> may be printed onto a non-conducive material as mentioned above. Alternatively, the traces <NUM> may be formed using conductive threads that are integrated into/onto the non-conductive material, e.g. a fabric. Incorporating the traces <NUM> into/onto the spacer layer <NUM> may simplify manufacture and assembly of the device <NUM>. <FIG> shows the corresponding example pressure area map that may be obtained from the insole device <NUM> of <FIG> when worn by a user.

Although <FIG> and <FIG> are shown as comprising a sensing layer <NUM> with a plurality of gapped portions <NUM>, it will be appreciated that the device <NUM> may be formed with one or more a sensing layers <NUM> without any gapped portions <NUM>.

<FIG> show an embodiment of the sensing layer <NUM> comprising three spacers <NUM> extending from the inner surface 10i of the first electrode <NUM> and three corresponding openings <NUM> formed in the second electrode <NUM>. In this example, the spacers <NUM> and openings <NUM> are arranged in a linear array. The first electrode <NUM> is the sense electrode with sensing points S1, S2 at each end of the array, and the second electrode <NUM> is the reference electrode for connecting to ground. Additional sensing points may be provided around the periphery of the sense electrode. In this example, the width of the sensing layer <NUM> is approximately <NUM>. In use, the lower electrode, in this case the second electrode <NUM> can be secured to the surface S, e.g. by an adhesive. <FIG> shows an example pressure area map that may be obtained from the sensing layer <NUM> of <FIG> when pressure is applied in two locations. As with <FIG> and <FIG>, each circle represents a XY location on the map, and the radius of each circle represents the magnitude of the determined pressure or force at that location.

<FIG> show an alternative embodiment of the sensing layer <NUM> comprising a larger array of spacers <NUM> and openings <NUM>. In this example, the second electrode <NUM> is the sense electrode with a plurality of sensing points S1-S4 distributed around its periphery and the first electrode <NUM> is the reference electrode for connecting to ground ( although either of the first and second electrodes <NUM>, <NUM> may be used as the sense electrode).

The measurement module <NUM> is configured to operate in a first mode and a second mode. In the first mode, the switching unit <NUM> scans through each sensing point S1, S2 one by one, so that the sensing circuit <NUM> can obtain a measurement or reading from each individual sensing point S1, S2 separately. In the second mode, the switching unit <NUM> connects all sensing points S1, S2 to the sensing circuit <NUM>, such that the sensing circuit <NUM> can obtain a single measurement or reading of capacitance from all sensing point S1, S2 simultaneously. In this way, each sensing point S1, S2 contributes to the measurement or reading in the second mode. In the first mode, only one sensing point S1, S2 is actively connected to the sensing circuit <NUM> at a given time. For example, while a measurement or reading is being taken from one sensing point S1, S2, other (non-active) sensing points S1, S2 may be disconnected from the sensing circuit. The scan frequency may be sufficiently high compared to a typical movement of the body to minimise any measurement lag, e.g. such that the measurement/detection may be perceived to be in real-time. For example, the scan rate may be in the range <NUM>-<NUM>. The scan rate may be slower or faster depending on the application. The measurement module <NUM> is configured to periodically and/or continuously switch/alternate between the first and second modes of operation during operation of the device <NUM>. Each period provides a reading or measurement cycle C1 comprising N+<NUM> readings, where N is the number of sensing points S1, S2. In an embodiment, the switching unit <NUM> is controlled by the control unit <NUM> and thus the first and second modes are controlled by the control unit <NUM>.

<FIG> show an example measurement cycle for a sensing layer <NUM>, <NUM>, <NUM> with two sensing points S1 and S2, where each sensing point S1, S2 is connected to the switching unit <NUM> that provides a single output to the input pin <NUM> of the sensing circuit <NUM>. Each switching element SW1, SW2 is controllable (via the control unit <NUM>, not shown) to switch between a closed state in which the respective sensing point S1, S2 is connected to the input pin <NUM>, and an open state in which the respective sensing point S1, S2 is disconnected from the input pin <NUM>. The reading cycle C1 comprises three readings, two in the first operating mode and one in the second operating mode. To generate a first reading in the first operating mode, switch SW1 is closed and switch SW2 is opened, thus capturing a reading from sensing point S1 at the input pin <NUM> (see <FIG>). To generate a second reading in the first operating mode, switch SW1 is opened and switch SW2 is closed, thus capturing a reading from sensing point S2 at the input pin <NUM> (see <FIG>). To generate a reading in the second operating mode, both switches SW1, SW2 are closed, thus capturing a reading from both sensing points S1, S2 at the input pin <NUM> (see <FIG>).

Readings from individual sensing points S1, S2 in the first mode and all the sensing points S1, S2 simultaneously in the second mode are used to determine a location, area and amount of the applied pressure, as is described in more detail below. The measurement cycle C1 is repeated (continuously or periodically) to monitor changes in the pressure and interaction with the sensing layer <NUM>, <NUM>, <NUM> in near-real time.

The capacitance measurement or reading from each sensing point S1, S2 is positively related to the amount of applied pressure. Due to the relatively high resistivity of the electrode material, the capacitance measurement or reading produced by a given applied pressure decays with distance (x) from the sensing point S1, S2. The reading from each individual sensing point S1, S2 is therefore related to the distance/proximity of the area/location of applied pressure from/to the sensing point S1, S2 and also the amount of applied pressure. As the geometry of the sensing layer <NUM>, <NUM>, <NUM> and the position/location of sensing points S1, S2 on the sensing layer <NUM>, <NUM>, <NUM> is known, the location and area of the applied pressure on the sensing layer <NUM>, <NUM>, <NUM> can be determined by calculating the distances of the forced location from each sensing points S1, S2, and then calculating a location and area from those distances.

Readings from individual sensing points S1, S2 can be mapped to distances x based on a known dependence of a reading on distance x. For example, this relationship can be approximated by the exponential function f(x) = e-nx, where e represents a constant and n is an adjustable parameter representing the decay rate, which can be determined/derived experimentally. Based on the value of the capacitance reading recorded at each sensing point S1, S2 a circle with a radius x<NUM>, x<NUM> defined by the reading value can be defined for each sensing point S1, S2. The circles drawn from each sensing point S1, S2 outline the perimeter of the area A of the applied pressure. According, this approach can be used to re-construct the location and area A of the applied pressure (hatched area), as shown in <FIG>. It follows that the greater the number of sensing points (circles) the greater the accuracy and spatial resolution of the pressure area mapping. However, it will be appreciated that, the sensing layer <NUM>, <NUM>, <NUM> may comprise any number N of sensing points S1, S2,. SN, depending on the needs of the application. One or two sensing points S1, S2 provides one-dimensional (e.g. X or Y) position/area sensing, while three or more sensing points S1, S2 can provide two-dimensional (e.g. XY) position/area sensing.

The readings obtained in the first mode of operation are used to determine the location, area and/or amount of the applied pressure. Although a rectangular area A is shown in <FIG>, it will be appreciated that any arbitrary shaped area A may be determined using this approach. The reading obtained in the second operating mode provides information on the total pressure applied to the whole sensing layer <NUM>, <NUM>, <NUM> that can be used in conjunction with the first mode measurements to improve the accuracy/reliability of the determined location, area and/or amount of applied pressure. For example, due to the fact that the readings obtained in the first mode are dependent on both the amount of applied pressure and the distance x, the second mode reading can used to confirm whether the readings obtained in the first mode correspond to a small amount of pressure distributed over a large area, or vice versa. The two modes combined therefore provide a more reliable pressure area map.

The pressure area maps or information obtained from the device <NUM> may be qualitative (i.e. providing normalised or relative values) or quantitative (i.e. where real values of pressure are required). Where quantitative data is required, the capacitance readings can be converted to a pressure value using a pre-determined relationship. For example, the device may be calibrated using known values of applied pressure.

<FIG> show example reading cycles C1, C2 (see right hand side of figures) obtained from a sensing layer <NUM>, <NUM>, <NUM> with two sensing points S1, S2 subject to a pressure or force profile A, indicated by the hatched regions (see left hand side of figures). Each cycle C1, C2 comprises three readings (i.e. N+<NUM>), as described above. <FIG> and b indicate the different readings obtained with, respectively, a low and high pressure/force applied to the same size area A and location on the sensing layer <NUM>, <NUM>, <NUM>. Figures 11c-d indicate how the readings vary with different locations and different sized areas of applied pressure/force. In particular, figures 11d and 11e show that different readings are obtained for different sized areas in the same centre location, i.e. pressure profiles. This information is used to build an accurate pressure area map of the interaction with the sensing layer <NUM>, <NUM>, <NUM>, as described above.

As discussed above, the ability to resolve the spatial location and area of the applied pressure relies on the resistivity of the electrode material being relatively high. As shown in <FIG>, the resistivity and/or resistance of the first electrode <NUM> and/or the second electrode <NUM> may be tuned without changing the intrinsic material properties by introducing one or more holes, hollows, cut-outs, recesses, thickness variations, and/or repeating geometric patterns/tracks to the electrode geometry. This provides a predetermined resistance between any two given points. The holes, hollows, cut-outs and/or recesses may form a regular or irregular array. The one or more holes, hollows and/or recesses may define a non-linear conduction path between any two points. Alternatively or additionally, the one or more hollows and/or recesses may define a plurality of linear and/or non-linear conduction paths between the two points.

The first and second electrodes <NUM>, <NUM> can be produced with a number of different inexpensive materials and fabrication techniques, as described above. The first and second electrodes <NUM>, <NUM> and any spacer layer <NUM> can be formed/moulded separately and then post-assembled together. The materials and their properties can be chosen to match the properties required by the application, e.g. shoe insoles, automobile interiors, and wearables. In addition, the first and second electrodes <NUM>, <NUM> can be formed or moulded into almost any arbitrary size, shape or three-dimensional (3D) form due to the nature of the moulding process, e.g. see <FIG> and <FIG>. For example, although <FIG> shows the sensing layer <NUM>, <NUM>, <NUM> and electrodes <NUM>, <NUM> in a substantially planar configuration, the sensing layer <NUM>, <NUM>, <NUM> and electrodes <NUM>, <NUM> may be formed/moulded to conform the exterior/interior surface S of any arbitrarily shaped object, regardless of complexity, as shown in <FIG>. The sensing layer <NUM> may be formed/moulded into the required shape as shown in <FIG> a ,b, d and e. Alternatively, where both first and second electrodes <NUM>, <NUM> and any spacer layer <NUM> is flexible, the sensing layer <NUM>, <NUM>, <NUM> can be deformed to conform to the surface profile S. In some applications, a cylindrical configuration, as shown in <FIG>may be utilised to provide easier mechanical connection of the sensing points S1-S4 to the measurement module <NUM>, e.g. since the sensing points S1-S4 may be located in closer proximity compared to a substantially planar configuration.

Further, it will be appreciated that the Z direction shown in <FIG>, <FIG> and <FIG> is not necessarily the vertical axis, such that the sensing layer <NUM>, <NUM>, <NUM> may arranged in any orientation.

<FIG> shows a generic system <NUM> comprising multiple separate sensing layers <NUM> whose readings can be combined to form a single pressure area map, e.g. through a computer program or software running on the control unit <NUM> or a remote computing device.

<FIG> shows an embodiment of the system <NUM> of multiple sensing layers <NUM> incorporated into a seat. As with the insole device <NUM> of <FIG> each sensing layer <NUM> provides information on the location, area and amount of the applied pressure or force from a specific area in the system <NUM>. The information from each sensing layer <NUM> can be combined through software to create a global pressure map of a complex sensor system <NUM>, effectively treating the multiple sensing layers <NUM> as a single large sensing layer <NUM> or pressure mapping area. For example, in the seat system <NUM> of <FIG>, the multiple sensing layers <NUM> may be used to obtain weight distribution from which different seating behaviours can be derived, as indicated by the vertical bars in <FIG>. Each different sensing layer <NUM> of the system <NUM> may connect to the same sensing input <NUM> of the sensing circuit <NUM>, e.g. via one or more switching units <NUM>. Alternatively, each different sensing layer <NUM> may connect to a different sensing input <NUM>.

In addition to applications in foot and seat pressure mapping, the device <NUM> may be incorporated into numerous everyday objects that users interact with. <FIG> shows an embodiment of the sensing layer <NUM> moulded and integrated in a phone case that can be used to extend the trackpad functions of a modern touchscreen phone.

<FIG> shows an embodiment of the sensing layer <NUM> used as a laptop trackpad. The sensing layer <NUM> can be used to replace conventional trackpads based on touch/pressure sensor arrays with unitary non-metallic electrodes that are produced cheaply, and require fewer sensing input pins and sensing points to provide precise location information.

<FIG> and <FIG> show further embodiments of the sensing layer <NUM> incorporated into common surfaces (e.g. a wall and table surface) to provide touch screens and/or interactive boards.

Embodiments of the invention provide a sensing layer <NUM>, <NUM>, <NUM> that produces a single capacitance reading from single sensing point S1, S2 indicative of interaction of a body/object with the sensing layer <NUM>, <NUM>, <NUM> that can be registered via a single input pin <NUM> of the sensing circuit <NUM>. Adding two or more sensing points S2, S2 and switching between them can advantageously provide complementary information about the forced area and allows a more accurate location or pressure/force profile to be built-up. This is because the reading from each sensing point S1, S2 will differ based on the relative proximity/location of the applied pressure/force or localised interaction with the sensing layer <NUM>, <NUM>, <NUM> to each sensing point S1, S2.

Claim 1:
A pressure sensing device (<NUM>) comprising:
a first electrode (<NUM>) and a second electrode (<NUM>) being formed of or comprising a unitary piece of non-metallic conductive material, wherein the first electrode and second electrode are spaced apart from each other by a distance that is changeable in response to a pressure or force applied to the first and/or second electrode; and
a measurement module (<NUM>) connected to the first or second electrode at a plurality of sensing points (S1, S2) on said electrode, wherein the measurement module is configured to:
measure a change in capacitance between the first and second electrode, in response to a change in the distance when a pressure or force is applied to the first and/or second electrode, at each sensing point individually and at all sensing points simultaneously;
map each measurement obtained from an individual sensing point to a distance of the applied pressure/force from said individual sensing point; and
determine the location, area and the amount of the applied pressure on the first and/or second electrode from the individual measurements and mapped distances, and the amount of the applied pressure from the simultaneous measurement.