Field of the invention The present invention relates particularly, but not exclusively, to a force sensor and methods of use and manufacture thereof. The present invention also relates to a system and/or an electrical component comprising a force sensor. Background to the invention

Resistive force sensors, or pressure sensors, can be formed from two opposing electrically conductive (or resistive) elements separated by a cavity. Typically, the user of the force sensor can press one conductive element against the other, which forms an electrical current flow path between the two conductive elements. When the user releases the applied force, the two conductive elements typically return to a rest position and are separated once again by the cavity. Thus, the resultant change in electrical conductivity between the two electrically conductive elements can be detected using ancillary electronics.

However, such known resistive force sensors are often difficult and expensive to manufacture using conventional electronics manufacturing techniques. Furthermore, such sensors are often prone to breakage due to the movement of at least one of the conductive elements across the cavity.

The inventor has appreciated the shortcomings in known force sensors, and methods of manufacture thereof. According to a first aspect of the present invention there is provided a force sensor comprising:

a force sensing element;

one or more first electrically conductive elements arranged to be in electrical communication with a first region of the force sensing element; one or more second electrically conductive elements arranged to be in electrical communication with a second region of the force sensing element; and

one or more third electrically conductive elements arranged to be in electrical communication with a third region of the force sensing element; wherein at least a part of the force sensing element is configured or configurable to have anisotropic electrical conductivity.

The force sensor may comprise a plurality of force sensing elements, each force sensing element being in electrical communication with at least one of the one or more first, second and third electrically conductive elements.

It should be understood that the term“conductive element” could comprise electrically conductive elements and/or electrically resistive elements, unless the context dictates otherwise.

The first electrically conductive element, the second electrically conductive element and/or the third electrically conductive element may be

electrodes. The first electrically conductive element, the second electrically conductive element and/or the third electrically conductive element may be electrically resistive elements.

The force sensing element may comprise an x, y and z axis. The force sensor may comprise one or more substrates. The, or each, substrate may be flexible. The, or each, substrate may be a substantially planar member. The, or each, substrate may be made from a plastics material. The, or each, substrate may be made from polyethylene terephthalate (PET), paper, impregnated paper, coated paper, phenolic paper, FR4, polyimide, polytetrafluoroethylene, metal core printed circuit board, polyurethane, polypropylene, polycarbonate, polyethylene terephthalate, polyvinylchloride, nylon, cellulose, cellophane, polyolefin, acrylonitrile butadiene styrene, polystyrene, high-density polyethylene, glass, and/or metal. The, or each, substrate can be made from any suitable substrate for supporting an electronic circuit, an electronic component, or the like.

The, or each, substrate may be configured to permit electromagnetic radiation to pass therethrough. The, or each, substrate may be configured to permit electromagnetic radiation in the visible wavelengths to pass therethrough. The force sensing element may be configured to permit electromagnetic radiation to pass therethrough. The force sensing element may be configured to permit electromagnetic radiation in the visible wavelengths to pass therethrough. The first, second and/or third electrically conductive elements may be configured to permit

electromagnetic radiation to pass therethrough. The first, second and/or third electrically conductive elements may be configured to permit electromagnetic radiation in the visible wavelengths to pass therethrough.

The first, second and/or third electrically conductive elements may be located on the, or each substrate. At least a part of the force sensing element may be located adjacent to the, or each substrate. At least a part of the force sensing element may be located on the, or each substrate. The, or each substrate may be arranged to provide support to the first, second, and/or third electrically conductive elements and/or the force sensing element.

The force sensor may comprise first and second substrates. The first, second and/or third electrically conductive elements may be located adjacent to, or on, the first and/or second substrates. The first and second electrically conductive elements may be located adjacent to, or on the first substrate and the third electrically conductive element may be located adjacent to, or on the second substrate.

The first and second substrates may be arranged along an axis from each other. The axis may be the z axis. It should be understood that the second substrate could be a“top layer” or“encapsulation layer”, or the like. The first and second substrates may be arranged to substantially surround the first, second, and/or the third electrically conductive elements and/or the force sensing element.

The first electrically conductive element may be located adjacent to the force sensing element. The first electrically conductive element may be located adjacent to the first region of the force sensing element. The first electrically conductive element may be connected to the first region of the force sensing element. The first electrically conductive element may be arranged to be in electrical contact with the first region of the force sensing element. The first electrically conductive element may be arranged to be in electrical contact with one or more surfaces of the first region of the force sensing element.

The second electrically conductive element may be located adjacent to the force sensing element. The second electrically conductive element may be located adjacent the second region of the force sensing element. The second electrically conductive element may be connected to the second region of the force sensing element. The second electrically conductive element may be arranged to be in electrical contact with the second region of the force sensing element. The second electrically conductive element may be arranged to be in electrical contact with one or more surfaces of the second region of the force sensing element.

The third electrically conductive element may be located adjacent to the force sensing element. The third electrically conductive element may be located adjacent to the third region of the force sensing element. The third electrically conductive element may be connected to the third region of the force sensing element. The third electrically conductive element may be arranged to be in electrical contact with the third region of the force sensing element. The third electrically conductive element may be arranged to be in electrical contact with one or more surfaces of the third region of the force sensing element.

The first electrically conductive element and the second electrically conductive element may be arranged to be spaced apart. The force sensor may comprise a plurality of first and second electrically conductive elements arranged in an inter-digited pattern. It will be appreciated that the first and second electrically conductive elements may be arranged in a wide range of arrangements.

The first and second regions of the force sensing element may be displaced from the third region of the force sensing element along the z- axis of the force sensing element. The first electrically conductive element and the second electrically conductive element may be arranged to be substantially co-planar. The first and second electrically conductive elements may be arranged to be displaced a distance from the third electrically conductive element along the z axis of the force sensing element.

The force sensing element may be arranged to substantially surround at least a part of the first electrically conductive element and/or at least a part of the second electrically conductive element in an x-z plane. The force sensing element may be arranged to surround a first part of the first electrically conductive element and/or a first part of the second electrically conductive element, and the substrate may be arranged to surround a second part of the first electrically conductive element and/or a second part of the second electrically conductive element, in the x-z plane.

The first and second regions of the force sensing element may be located at a first end of the force sensing element. The third region of the force sensing element may be located at a second end of the force sensing element. The third region of the force sensing element may be arranged along an axis from the first and/or second regions of the force sensing element. At least a part of the third region of the force sensing element may be arranged along an axis from the first region of the force sensing element and at least a part of the third region of the force sensing element may be arranged along an axis from the second region of the force sensing element.

At least a part of the third electrically conductive element may be arranged along an axis from the first electrically conductive element and at least a part of the third electrically conductive element may be arranged along an axis from the second electrically conductive element. The force sensor may be configured to be electrically connectable to one or more further force sensors. The force sensor may be configured to be electrically connectable to one or more electronic circuits.

At least a part of the force sensor may be flexible. At least a part of the force sensor may be substantially planar. The force sensor may be a thin- film force sensor.

The force sensor may be a multi-layered structure and each layer of the structure may be arranged to be in conformal contact with another layer of the structure. The force sensor may be arranged in a stacked

arrangement, that is a series of layers sequentially stacked on top of each other. The first electrically conductive element may be arranged to be in conformal contact with the first region of the force sensing element. The second electrically conductive element may be arranged to be in conformal contact with the second region of the force sensing element.

The third electrically conductive element may be arranged to be in conformal contact with the third region of the force sensing element. The first, second, and/or third electrically conductive elements and/or the force sensing element may be arranged to be in conformal contact with the, or each, substrate. The force sensor may be arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. The force sensing element may be arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. The first, second and/or third electrically conductive elements may be arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. The one or more substrates may be arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. The force sensing element may be a flexible element. The force sensing element may be a planar element. The force sensing element may be a substantially uniform layer. The force sensing element may be a substantially continuous layered structure. That is, a structure

substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like.

Substantially all of the force sensing element may be configurable or configured to have anisotropic electrical conductivity. The force sensing element may be formed from an anisotropic electrical conductivity ink, a printed anisotropic conductivity material, or the like. The force sensing element may be a printed layer. The force sensing element may be formed from a film, and/or tape, or the like. The force sensing element may be formed from a pressure sensitive adhesive. The force sensing element may be formed from anisotropic electrically conductive tape, or the like. The force sensing element may be formed from an at least partially adhesive film, tape, or the like. The force sensing element may comprise silicone. The force sensing element may comprise an anisotropic conductive material and silicone.

At least a part of the force sensing element may be configured to be a fluid at room temperature. The fluid may include one or more liquids and one or more solids. In this arrangement, compression of the force sensing element displaces the liquid(s), such that the solids form an electrically conductive path.

The force sensing element may be configured to be deformable between a first, rest position and a second, deformed position. The force sensing element may be configured to be moveable between the first, rest position and the second, deformed position. The force sensing element may be configured to be reversibly deformable between the first, rest position and the second, deformed position. The force sensing element may be configured to be reversibly moveable between the first, rest position and the second, deformed position. The force sensing element may be reversibly compressible. The force sensing element may be reversibly compressible between the first, rest position and the second, deformed position. The force sensing element may be configured to have one or more first values of electrical conductivity at the first, rest position and one or more second values of electrical conductivity at the second, deformed position. The force sensing element may be configured to have

substantially the same electrical conductivity in the direction of the x-axis and y-axis of the force sensing element when moved between the first, rest position and the second, deformed position.

The force sensing element may be configured or configurable to have relatively high electrical conductivity in the direction of the z-axis of the force sensing element and relatively low electrical conductivity in the direction of the x-axis and y-axis of the force sensing element. The force sensing element may be configured to have substantially zero electrical conductivity in the direction of the x-axis and y-axis of the force sensing element.

The force sensor may be configured to have an electrical current flow path from the first electrically conductive element, through the force sensing element, through the third electrically conductive element, through the force sensing element, through the second electrically conductive element and/or vice versa. The electrical current flow path of the force sensor may be configured to be shorter at the second, deformed position than at the first, rest position. The force sensing element may be a resilient element. The force sensing element may be an elastic element. The force sensing element may be a pressure sensitive element, or a pressure sensitive adhesive element.

The force sensing element may be a pressure activated semiconductor. The force sensing element may be configured to change its electrical conductivity, in at least one direction of measurement, in response to applied force.

The force sensing element may comprise one or more discrete electrical conducting elements. The force sensing element may comprise one or more discrete non-conducting elements. The force sensing element may comprise one or more discrete conducting elements and one or more discrete non-conducting elements. The discrete conducting elements may be arranged adjacent to each other. The discrete conducting elements may be arranged to form an electrical current flow path. The discrete conducting elements may be arranged to form an electrical current flow path substantially in the z-axis direction. The force sensing element may be configured such that the discrete conducting elements are not arranged to form an electrical current flow path at the first, rest position, and are arranged to form an electrical current flow path at the second, deformed position. The one or more discrete conducting elements may be microspheres, or the like. The one or more discrete conducting elements may comprise one or more metals. The one or more discrete conducting elements may comprise silver, copper, indium tin oxide, one or more carbon nanotubes, and/or one or more carbon nanobuds. The one or more discrete non-conducting elements may be configured to be a liquid at room temperature.

The first, second and/or third electrically conductive elements may comprise a resistive element. At least a part of the first, second and/or third electrically conductive elements may be configured to permit electromagnetic radiation to pass therethrough. At least a part of the first, second and/or third electrically conductive elements may be configured to permit electromagnetic radiation in the visible wavelengths to pass therethrough. The first, second and/or third electrically conductive elements may be made from a printed material. The first, second and/or third electrically conductive elements may be made from one or more metals. The first, second and/or third electrically conductive elements may be made from silver, copper, indium tin oxide, carbon, graphite, graphene, palladium, carbon nanotubes and/or carbon nanobuds. The first, second and/or third electrically conductive elements may be formed from an ink solution comprising one or more metals. The first, second and/or third electrically conductive elements may be formed from high-conductivity silicon. The first, second and/or third electrically conductive elements may be formed using a plating process. The plating process may be an electroless plating process. The first, second and/or third electrically conductive elements may be formed using an injection moulding process. The injection moulding process may be a conductive injection moulding process.

The first, second and/or third electrically conductive elements may be substantially planar. The first, second and/or third electrically conductive elements may be thin-film elements. The first, second and/or third electrically conductive elements may be flexible elements. The force sensor may be configured to be a substantially flexible member.

The first electrically conductive element may be a printed electrode. The first electrically conductive element may have high electrical conductivity or may be configured to have high electrical conductivity. The first electrically conductive element may have substantially isotropic electrical conductivity or may be configured to have substantially isotropic electrical conductivity.

The second electrically conductive element may be a printed electrode. The second electrically conductive element may have high electrical conductivity, or may be configured to have high electrical conductivity.

The second electrically conductive element may have substantially isotropic electrical conductivity, or may be configured to have substantially isotropic electrical conductivity.

The third electrically conductive element may be a printed electrode. The third electrically conductive element may have high electrical conductivity, or may be configured to have high electrical conductivity. The third electrically conductive element may have substantially isotropic electrical conductivity, or may be configured to have substantially isotropic electrical conductivity.

The first electrically conductive element may be a resistive element. The first electrically conductive element may be made from a resistive material, or a resistive ink.

The second electrically conductive element may be a resistive element. The second electrically conductive element may be made from a resistive material, or a resistive ink.

The third electrically conductive element may be a resistive element. The third electrically conductive element may be made from a resistive material, or a resistive ink. The first electrically conductive element and the force sensing element may be configured such that the electrical contact resistance

therebetween is variable between one or more first values at the first, rest position and one or more second values at the second deformed position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the first electrically conductive element and the force sensing element can vary between one or more relatively high values at the first, rest position, and one or more relatively low values at the second, deformed position. Thus, the first electrically conductive element and the force sensing element are, in this

arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element.

The second electrically conductive element and the force sensing element may be configured such that the electrical contact resistance

therebetween is variable between one or more first values at the first, rest position and one or more second values at the second, deformed position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the second electrically

conductive element and the force sensing element can vary between one or more relatively high values at the first, rest position, and one or more relatively low values at the second, deformed position. Thus, the second electrically conductive element and the force sensing element are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element.

The third electrically conductive element and the force sensing element may be configured such that the electrical contact resistance therebetween is variable between one or more first values at the first, rest position and one or more second values at the second, deformed position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the third electrically conductive element and the force sensing element can vary between one or more relatively high values at the first, rest position, and one or more relatively low values at the second, deformed position. Thus, the third electrically conductive element and the force sensing element are, in this

arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element.

The first electrically conductive element and the force sensing element may be configured to be movable between a first contact position and a second contact position. The first electrically conductive element and the force sensing element may be configured such that the electrical contact resistance therebetween is variable between one or more first values at the first contact position and one or more second values at the second contact position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the first electrically conductive element and the force sensing element can vary between one or more relatively high values at the first contact position, and one or more relatively low values at the second contact position.

Thus, the first electrically conductive element and the force sensing element are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element.

The second electrically conductive element and the force sensing element may be configured to be movable between a first contact position and a second contact position. The second electrically conductive element and the force sensing element may be configured such that the electrical contact resistance therebetween is variable between one or more first values at the first contact position and one or more second values at the second contact position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the second electrically conductive element and the force sensing element can vary between one or more relatively high values at the first contact position, and one or more relatively low values at the second contact position. Thus, the second electrically conductive element and the force sensing element are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element.

The third electrically conductive element and the force sensing element may be configured to be movable between a first contact position and a second contact position. The third electrically conductive element and the force sensing element may be configured such that the electrical contact resistance therebetween is variable between one or more first values at the first contact position and one or more second values at the second contact position. The first value may be higher than the second value. In this arrangement, the electrical contact resistance between the third electrically conductive element and the force sensing element can vary between one or more relatively high values at the first contact position, and one or more relatively low values at the second contact position.

Thus, the third electrically conductive element and the force sensing element are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element. According to a second aspect of the present invention there is provided a method of manufacturing a force sensor, the method comprising the steps of: providing one or more first electrically conductive elements and one or more second electrically conductive elements;

providing a force sensing element, wherein at least a part of the force sensing element is configured or configurable to have anisotropic electrical conductivity;

arranging the one or more first electrically conductive elements to be in electrical communication with a first region of the force sensing element;

arranging the one or more second electrically conductive elements to be in electrical communication with a second region of the force sensing element;

providing one or more third electrically conductive elements; and arranging the one or more third electrically conductive elements to be in electrical communication with a third region of the force sensing element.

The method may comprise the step of arranging the one or more first electrically conductive elements to be electrically connected to the first region of the force sensing element. The method may comprise the step of arranging the one or more first electrically conductive elements to be substantially adjacent to the first region of the force sensing element. The method may comprise the step of arranging the one or more first electrically conductive elements to be in conformal contact with the first region of the force sensing element.

The method may comprise the step of arranging the one or more second electrically conductive elements to be electrically connected to the second region of the force sensing element. The method may comprise the step of arranging the one or more second electrically conductive elements to be substantially adjacent to the second region of the force sensing element. The method may comprise the step of arranging the one or more second electrically conductive elements to be in conformal contact with the second region of the force sensing element.

The method may comprise the step of arranging the one or more third electrically conductive elements to be electrically connected to the third region of the force sensing element. The method may comprise the step of arranging the one or more third electrically conductive elements to be substantially adjacent to the third region of the force sensing element. The method may comprise the step of arranging the one or more third electrically conductive elements to be in conformal contact with the third region of the force sensing element.

The method may comprise the step of providing one or more substrates. The method may comprise the step of arranging the first and second electrically conductive elements on the one or more substrates. The method may comprise the step of arranging the force sensing element on the one or more substrates. The method may comprise the step of arranging the third electrically conductive element on the one or more substrates. The method may comprise the step of providing at least two substrates, arranging the first and second electrically conductive elements on a first substrate, arranging the force sensing element on the first substrate, arranging the third electrically conductive element on the force sensing element, and arranging a second substrate on the third electrically conductive element.

The method of manufacturing the force sensor may be carried out using one or more additive manufacturing techniques, or processes. The method may be carried entirely using additive manufacturing techniques, or processes. The additive manufacturing technique, or process may be a printing process.

At least one of the steps of the method may be carried out using an additive manufacturing process. At least one of the steps of the method may be carried out using a deposition process. At least one of the steps of the method may be carried out using an etching process. The additive manufacturing process may be a die cut process, a die attachment process, and/or a tape attachment process, or the like. At least one of the steps of the method may be carried out using a lithography process. The lithography process may be a photolithography process.

At least one of the steps of the manufacturing process may be carried out using a laser patterning process. The laser patterning process may be a laser ablation process.

At least one of the steps of the method may be carried out using one or more printing processes. The step of arranging the first electrically conductive element on the one or more substrates may be carried out using one or more printing processes. The step of arranging the second electrically conductive element on the one or more substrates may be carried out using one or more printing processes. The step of arranging the first and second electrically conductive elements on the one or more substrates may be carried out using one or more printing processes. The step of arranging the force sensing element on the one or more substrates may be carried out using a printing process. The step of arranging the first and second electrically conductive elements to be in electrical

communication with the first and second regions of the force sensing element may be carried out using a printing process. The step of arranging the third electrically conductive element to be in electrical communication with the third region of the force sensing element may be carried out using a printing process.

The printing process may be a screen printing process, a flexography printing process, an offset printing process, an inkjet printing process, an aerosol printing process, a digital thermal transfer ribbon process, a thermal transfer printing process, a transfer printing process, a thermal transfer printing process, a digital printing process, a lamination printing process, an in-line printing process, and/or a printed circuit board printing process.

The printing process may be a wet deposit technique. The printing process may be a gravure process, or an offset process.

It should be understood that at least one of, or each step of the method may be carried out using any one, or one or more, of the printing

processes, additive manufacturing processes, etching processes and/or deposition processes described herein.

The step of arranging the first and second electrically conductive elements on the one or more substrates may be carried out using an attachment process, a die-cut attachment process, or the like. The step of arranging the force sensing element on the one or more substrates may be carried out using an attachment process, a die-cut attachment process, or the like. The step of arranging the third electrically conductive element on the force sensing element may be carried out using an attachment process, a die- cut attachment process, or the like. The step of arranging the first electrically conductive element to be in electrical communication with the first region of the force sensing element may be carried out using an attachment process, a die-cut attachment process, or the like. The step of arranging the second electrically conductive element to be in electrical communication with the second region of the force sensing element may be carried out using an attachment process, a die-cut attachment process, or the like. The step of arranging the third electrically conductive element to be in electrical communication with the third region of the force sensing element may be carried out using an attachment process, a die-cut attachment process, or the like.

The first, second and/or third electrically conductive elements may be provided from one or more inks, ink solutions, conductive inks and/or resistive inks. The first, second and/or third electrically conductive elements may be provided from one or more conductive inks comprising one or more metals. The first, second, and/or third electrically conductive elements may be provided from one or more conductive inks comprising silver, copper and/or indium tin oxide. The first, second, and/or third electrically conductive elements may be provided from one or more resistive inks. The resistive ink may comprise one or more metals. The resistive ink may be a carbon-based ink or paste, and/or a metal loaded ink. The resistive ink may comprise graphite and/or graphene. The resistive ink may comprise one or more carbon nanotubes and/or one or more carbon nanobuds.

The first, second and/or third electrically conductive elements may be provided using an etching process, and/or a deposition process.

The force sensing element may be provided from one or more inks, ink solutions, and/or anisotropic electrical conductivity inks. The force sensing element may be a pressure sensitive adhesive. The force sensing element may be formed from an ink comprising one or more pressure sensitive adhesives. The force sensing element may be provided from one or more anisotropic electrical conductive inks comprising one or more metals. The force sensing element may be provided from one or more anisotropic electrical conductive inks comprising one or more discrete conductive elements. The force sensing element may be provided from one or more inks comprising silver, copper and/or indium tin oxide.

The method may comprise the step of providing one or more stamps, the one or more stamps being for use in one or more printing processes. The stamp may be for use in a transfer printing process. The, or each stamp may comprise one or more stamp substrates. The, or each stamp substrate may be made from a plastics material. The, or each stamp substrate may be made from polyester or polyethylene terephthalate. The stamp may comprise the first electrically conductive element. The stamp may comprise the second electrically conductive element. The stamp may comprise the first and the second electrically conductive element. The stamp may comprise the third electrically conductive element.

The step of arranging the first electrically conductive element to be in electrical communication with the first region of the force sensing element may be carried out using at least one stamp. The step of arranging the second electrically conductive element to be in electrical communication with the second region of the force sensing element may be carried out using at least one stamp. The step of arranging the first electrically conductive element to be in electrical communication with the first region of the force sensing element and the step of arranging the second electrically conductive element to be in electrical communication with the second region of the force sensing element may be carried out using a single stamp. The step of arranging the third electrically conductive element to be in electrical communication with the third region of the force sensing element may be carried out using at least one stamp.

The, or each stamp may be formed using one or more printing processes.

The method may comprise the step of attaching the force sensor to an electronic component. The method may comprise the step of connecting the force sensor to an electronic component. The method may comprise the step of attaching the force sensor to an electronic system. The method may comprise the step of connecting the force sensor to an electronic system. The method step of attaching the force sensor to an electronic system may be carried out using a moulding process. The moulding process may be an injection moulding process, or the like.

The method may comprise the step of including the force sensor within an electronic display.

It will be appreciated that the order that the steps are recited

is only exemplary, and that the steps may be carried out in any order except where it is clear that a specific order is meant and/or a specific order is required or essential for the proper functioning of the method or process.

Embodiments of the second aspect of the present invention may include one or more features of the first aspect of the present invention or its embodiments. Similarly, embodiments of the first aspect of the present invention may include one or more features of the second aspect of the present invention or its embodiments. According to a third aspect of the present invention there is provided an electrical component or electrical system comprising the force sensor of the first aspect of the present invention.

The system may be an electronic display, a fascia display, or the like. The system may be a keypad, a remote control, a switch, an on/off switch, an interconnect device, a moulded interconnect device, a touch-sensitive device, a touch-sensitive keypad, a gauge, a pressure sensing gauge, a speed control device, a motor speed control device, a security device, a pressure security device, a smart card, a smart card security device, an electronic component, an electronic security device, a packaging device, an interactive device, an interactive packaging device, an interactive touch packaging device, a substantially waterproof device, a substantially waterproof device complying with the IP67 and/or IP68 codes, a

substantially waterproof switch, a pressure sensor, an automotive pressure sensor, a medical pressure sensor, an electronic seal, an electronic gasket, a strain gauge, or the like. The system may be a handle. The system may be any suitable three-dimensional object.

The system may comprise a battery. The system may comprise a light emitting element. The light emitting element may be a light emitting diode, or the like. The system may comprise an electrical current flow path formed from the battery, the first electrically conductive element of the force sensor, the second electrically conductive element of the force sensor, and the LED.

Embodiments of the third aspect of the present invention may include one or more features of the first and/or second aspects of the present invention or their embodiments. Similarly, embodiments of the first and/or second aspects of the present invention may include one or more features of the third aspect of the present invention or its embodiments.

According to a fourth aspect of the present invention there is provided use of the force sensor of the first aspect of the invention in an electrical component or system.

Embodiments of the fourth aspect of the present invention may include one or more features of the first, second and/or third aspects of the present invention or their embodiments. Similarly, embodiments of the first, second, and/or third aspects of the present invention may include one or more features of the fourth aspect of the present invention or its embodiments.

According to a fifth aspect of the present invention there is provided a force sensor comprising:

a force sensing element;

one or more first electrically conductive elements arranged to be in electrical communication with a first region of the force sensing element; one or more second electrically conductive elements arranged to be in electrical communication with a second region of the force sensing element; and

wherein at least a part of the force sensing element is configured or configurable to have anisotropic electrical conductivity.

Embodiments of the fifth aspect of the present invention may include one or more features of the first, second, third and/or fourth aspects of the present invention or their embodiments. Similarly, embodiments of the first, second, third and/or fourth aspects of the present invention may include one or more features of the fifth aspect of the present invention or its embodiments.

According to a sixth aspect of the present invention there is provided a system comprising the force sensor of the first aspect of the present invention.

Embodiments of the sixth aspect of the present invention may include one or more features of the first, second, third, fourth and/or fifth aspects of the present invention or their embodiments. Similarly, embodiments of the first, second, third, fourth and/or fifth aspects of the present invention may include one or more features of the sixth aspect of the present invention or its embodiments.

According to a seventh aspect of the present invention there is provided a system comprising the force sensor of the fifth aspect of the present invention.

Embodiments of the seventh aspect of the present invention may include one or more features of the first, second, third, fourth, fifth and/or sixth aspects of the present invention or their embodiments. Similarly, embodiments of the first, second, third, four, fifth and/or sixth aspects of the present invention may include one or more features of seventh aspect of the present invention or its embodiments.

According to an eighth aspect of the present invention there is provided a method of manufacturing a force sensor, the method comprising the steps of: providing one or more first electrically conductive elements and one or more second electrically conductive elements; providing a force sensing element, wherein at least a part of the force sensing element is configured/configurable to have anisotropic electrical conductivity;

arranging the one or more first electrically conductive elements to be in electrical communication with a first region of the force sensing element; and

arranging the one or more second electrically conductive elements to be in electrical communication with a second region of the force sensing element.

Embodiments of the eighth aspect of the present invention may include one or more features of the first, second, third, fourth, fifth, sixth and/or seventh aspects of the present invention or their embodiments. Similarly, embodiments of the first, second, third, four, fifth, sixth and/or seventh aspects of the present invention may include one or more features of eighth aspect of the present invention or its embodiments.

Brief description of the drawings Embodiments of the invention will now be described, by way of example, with reference to the drawings, in which:

Figs. 1 a to 1 c show a schematic view of a force sensor according to the present invention; and

Figs. 2a to 2e show a of a method of manufacturing the force sensor of Figs. 1 a to 1 c.

Description of preferred embodiments

With reference to Figs. 1 a to 1 c a force sensor 1 according to the present invention is shown. In the embodiments illustrated and described here, the force sensor 1 is a planar, flexible sensor, which can be integrated within a wide-range of electrical components and systems. The force sensor 1 is arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. That is, the first, second and third electrically conductive elements 2, 4, 8, the force sensing element 6 and the substrate 10 are arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. Although not shown, an encapsulation layer (i.e. the top substrate) is also arranged to be substantially devoid of cavities, air-gaps, gaps, and/or chambers, or the like. Thus, the force sensor 1 is easier, and less expensive, to manufacture, and the lifetime of the force sensor 1 is improved, over known cavity-type force sensors 1.

The force sensor 1 comprises a force sensing element 6 and a first electrically conductive element 2 is arranged to be in electrical

communication with a first region 6a of the force sensing element 6.

Similarly, a second electrically conductive element 4 is arranged to be in electrical communication with a second region 6b of the force sensing element 6. Furthermore, a third electrically conductive element 8 is arranged to be in electrical communication with a third region 6c of the force sensing element 6.

As best shown in Figs. 1 b and 1 c, at least a part of the force sensing element 6 is configured to have anisotropic electrical conductivity. In the embodiments illustrated and described here, the force sensing element 6 comprises an x, y and z axis 12x, 12y and 12z, and the anisotropic electrical conductivity of the force sensing element 6 results in an electrical current flow path 16 that is substantially in the direction of the z axis 12z of the force sensing element 6. Whilst in the embodiments illustrated and described here, at least a part of the force sensing element 6 is configured to have anisotropic electrical conductivity, it should be understood that in some embodiments the force sensing element 6 could be configurable to have anisotropic electrical conductivity. For example, the force sensing element 6 could be a printed layer, and the anisotropic electrical conductivity could be achieved by way of an activation mechanism, such as by thermal curing, or the like.

As described in more detail below, the first and second electrically conductive elements 2, 4 are, in the embodiments described here, electrical conductors, and the third electrically conductive element 8 is a resistive element. In this arrangement, the force sensor 1 comprises two electrodes (examples of first and second electrically conductive elements 2, 4) and a resistor, or resistive element (an example of a third electrically conductive element 8) separated by the force sensing element 6.

The force sensor 1 comprises a flexible, planar substrate 10 made from polyethylene terephthalate (PET). As shown in Fig. 1 a, the first and second electrically conductive elements 2, 4 are located on the substrate 10, as is the force sensing element 6.

Although not shown, it will be appreciated that the force sensor 1 will typically comprise an additional top substrate, or encapsulation layer, for protecting the upper part of the force sensor 1 while in use. In this arrangement, the substrates 10 are arranged to substantially surround the first, second, and the third electrically conductive elements 2, 4, 8 and the force sensing element 6.

As shown in Figs. 1 a to 1 c, the first electrically conductive element 2 is located adjacent to the first region 6a of the force sensing element 6 and is electrically connected thereto at three surfaces of the first region 6a of the force sensing element 6. It should be appreciated that in other

embodiments the first electrically conductive element 2 could be

connected to the force sensing element 6 in other ways.

Likewise, in the embodiment illustrated in Figs. 1 a to 1 c, the second electrically conductive element 4 is located adjacent to the second region 6b of the force sensing element 6 and is electrically connected thereto at three surfaces of the second region 6b of the force sensing element 6. It should be appreciated that in other embodiments the second electrically conductive element 4 could be connected to the force sensing element 6 in other ways.

As shown in Figs. 1 a to 1 c, the third electrically conductive element 8 is located adjacent to the third region 6c of the force sensing element 6 and is electrically connected thereto at a single surface of the third region 6c of the force sensing element 6. It should be appreciated that in other embodiments the third electrically conductive element 8 could be connected to the force sensing element 6 in other ways.

In the embodiment shown in Fig. 1 a, the first electrically conductive element 2 and the second electrically conductive element 4 are arranged to be spaced apart, and there is no direct electrical current flow path between them. In other embodiments, the force sensor 6 can comprise a plurality of first and second electrically conductive elements 2, 4 arranged in an inter-digited pattern.

In the embodiments illustrated and described here, the first and second regions 6a, 6b of the force sensing element 6 are displaced from the third region 6c of the force sensing element 6 along the z-axis 12z of the force sensing element 6. That is, because the anisotropic electrical conductivity of the force sensing element 6 is greatest along the z-axis 12z thereof, it is advantageous to locate the first and second regions 6a, 6b, and the third region 6c along the z-axis 12z.

In the embodiments illustrated and described here, the first and second electrically conductive elements 2 and 4 are arranged to be substantially co-planar, which makes the force sensor 1 easier to manufacture, as the first and second electrically conductive elements 2, 4 can be formed at essentially the same stage of the manufacturing process, optionally using the same process (e.g. a printing process, as described below and shown in Figs. 2a to 2e).

As shown in Figs. 1 a to 1 c, the third region 6c of the force sensing element 6 is arranged along the z axis 12z from the first and second regions 6a, 6b of the force sensing element 6. Flowever, in other embodiments, it may be sufficient for a part of the third region 6c of the force sensing element 6 to be arranged along the z axis 12z from the first region 6a of the force sensing element 6 and for a part of the third region 6c of the force sensing element 6 to be arranged along the z axis 12z from the second region 6b of the force sensing element 6.

Typically, the force sensor 1 is configured to be electrically connectable to one or more further force sensors, e.g. to form a sensor array, and the force sensor 1 is configured to be electrically connectable to one or more electronic circuits, such as signal processing circuity for converting changes in electrical resistance to digital signals (e.g. pulse-width modulation). This is typically achieved by way of an electrical connection to the first and second electrically conductive elements 2, 4. The force sensor 1 is a multi-layered structure and each layer of the structure is arranged to be in conformal contact with the other layer (i.e. the opposing layer) of the structure. That is, the force sensor 1 is arranged in a stacked arrangement, that is a series of layers sequentially stacked on top of each other. This makes the force sensor 1 of the present invention easier, and less expensive, to manufacture. The force sensor 1 is thus particularly suited for manufacture using conventional electronics manufacturing techniques, and/or using additive manufacturing techniques.

The force sensing element 6 is a planar, flexible element, although in some examples the force sensing element 6 need not be planar and flexible. In the embodiments illustrated and described here, the force sensing element 6 is a substantially uniform, and continuous layer (i.e. not having any cavities, air-gaps, or the like).

In the embodiments illustrated and described here, substantially all of the force sensing element 6 is configured to have anisotropic electrical conductivity. As described in more detail below, the force sensing element 6 is formed by printing an anisotropic electrical conductivity ink onto the substrate 10, and thus the force sensing element 6 is a printed layer.

However, it should be appreciated that the force sensing element 6 could be formed from a film, tape, or the like, including anisotropic conductive tape, or the like.

As best shown in Figs. 1 b and 1 c, the force sensing element 6 is configured to be deformable between a first, rest position 14a and a second, deformed position 14b in response to applied force 18. Thus, the force sensing element 6 is configured to be moveable between the first, rest position 14a and the second, deformed position 14b. This shortens the electrical current flow path 16 between the first and second electrically conductive elements 2, 4, which in turn contributes to a change in electrical conductivity, which can be detected using ancillary electronics.

In the embodiments illustrated and described here, the force sensing element 6 is configured to be reversibly deformable between the first, rest position 14a and the second, deformed position 14b. That is, the force sensor 1 is configured to return to the first, rest position 14a when no force is applied to the force sensor 1.

The force sensing element 6 is configured to have a first value of electrical conductivity at the first, rest position 14a and a second value of electrical conductivity at the second, deformed position 14b.

As best shown in Figs. 1 b and 1 c, the force sensing element is configured to have substantially zero electrical conductivity in the direction of the x- axis and y-axis 12x, 12y of the force sensing element 6 when moved between the first, rest position 14a and the second, deformed position 14b. That is, in this embodiment electrical current never flows directly between the first and second electrically conductive elements 2, 4, rather the electrical current can only flow therebetween via the force sensing element 6 and the third electrically conductive element 8. It will be appreciated that the design of the electrical conductivity, and the electrical conductance, of the third electrically conductive element and the force sensing element 6 can be used to, at least in part, control the operating parameters of the force sensor 1. It will be appreciated that the electrical conductance between the first and second electrically conductive elements 2, 4 will be determined in part by the geometrical properties of the force sensor 1. The force sensing element 6 illustrated and described here is configured to have relatively high electrical conductivity in the direction of the z-axis 12z of the force sensing element 6 and relatively low electrical conductivity in the direction of the x-axis and y-axis 12x, 12y of the force sensing element 6, ideally zero electrical conductivity in the direction of the x-axis and y-axis 12x, 12y.

Thus, as shown in Figs. 1 b and 1c, the force sensor 1 is configured to have an electrical current flow path 16 from the first electrically conductive element 2, through the force sensing element 6, through the third electrically conductive element 8, through the force sensing element 6, through the second electrically conductive element 4 and the electrical current flow path 16 of the force sensor 1 is configured to be shorter at the second, deformed position 14b than at the first, rest position 14a.

The force sensing element 6 is a resilient element.

Whilst in the embodiments illustrated and described here the force sensing element 6 is configured to change its electrical conductivity in substantially one direction of measurement, i.e. in the direction of the z-axis 12z, it will be appreciated from Fig. 1 c that the electrical conductivity effectively changes in one or more directions due to the deformation of the force sensing element 6 in response to applied force.

The force sensing element 6 comprises one or more discrete conducting elements, which are microspheres of metal, arranged adjacent to each other to form an electrical current flow path substantially in the z-axis 12z direction. In the embodiments illustrated and described here, the third electrically conductive element 8 includes a resistive element and is formed from resistive ink. However, it should be understood that the third electrically conductive element 8 could include a conductive element and could be formed from other materials, such as a conductive ink.

In the embodiments illustrated and described here, the first, second and third electrically conductive elements 2, 4, 8 are substantially planar and are flexible.

The first and second electrically conductive elements 2, 4 are printed electrodes configured to have high electrical conductivity, and the third electrically conductive element 8 is a printed resistive element. However, it will be appreciated that the arrangement of the first, second and third electrically conductive elements 2, 4, 8 could be switched, such that the third electrically conductive element 8 is located on the substrate 10 and the first and second electrically conductive elements 2, 4 are arranged along the z axis 12z at an end of the force sensing element 6. Other arrangements will also be readily apparent to those skilled in the art.

In the embodiments illustrated here, the third electrically conductive element 8 and the force sensing element 6 are configured such that the electrical contact resistance therebetween is variable between one or more first values at a first contact position 14a’ and one or more second values at the second contact position 14b’. That is, the first value is higher than the second value. In this arrangement, the electrical contact resistance between the third electrically conductive element 8 and the force sensing element 6 can vary between a relatively high value at the first, rest position 14a, and a relatively low value at the second, deformed position 14b. Thus, the third electrically conductive element 8 and the force sensing element 6 are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element 6. Without wishing to be bound by theory, it is thought that this effect is caused by printing the third

electrically conductive element 8 onto the force sensing element 6.

However, it should be appreciated that the electrical contact resistance between the third electrically conductive element 8 and the force sensing element 6 could be configured to be negligible, such that the effect described above does not occur. In this case, the deformation of the force sensing element 6 is the main contributor to the change in electrical conductivity of the force sensor 1.

One of the benefits of configuring the force sensor 1 to have variable electrical contact resistance between at least one of the first, second and/or third electrically conductive elements 2, 4, 8 and the force sensing element 6 is that the force sensor 1 can be configured to have a relatively high“off” resistance when no force is applied and a relatively low“on” resistance when a force is applied. In the embodiments illustrated and described here, the off resistance is approximately 200 kQ and the on resistance is substantially 0 W.

With reference to Figs. 2a to 2e, a method of manufacturing the force sensor 1 is shown, the method comprising the steps of providing a first electrically conductive element 2 and a second electrically conductive element 4, providing a force sensing element 6, wherein at least a part of the force sensing element 6 is configured to have anisotropic electrical conductivity, arranging the first electrically conductive element 2 to be in electrical communication with a first region 6a of the force sensing element 6, arranging the one or more second electrically conductive elements 4 to be in electrical communication with a second region 6b of the force sensing element 6, providing a third electrically conductive element 8 and arranging the third electrically conductive element 8 to be in electrical communication with a third region 6c of the force sensing element 6.

As shown in Fig. 2a, the method comprises the initial step of providing a substrate 10 and arranging the first and second electrically conductive elements 2, 4 on the one or more substrates using an additive

manufacturing process. Indeed, all of the steps of the method that involve adding an element to the force sensor 1 are carried out using an additive manufacturing technique, specifically a printing process (including a transfer printing process, as illustrated in Fig. 2d). The step illustrated in Fig. 2a is, in this embodiment, carried out using a thermal transfer printing process. Flowever, it should be understood that other additive

manufacturing techniques could be used for this step.

Next, as shown in Figs. 2b and 2c the method comprises the step of arranging the force sensing element 6 on the substrate 10. During this step, the first and second regions 6a, 6b, of the force sensing element 6, are arranged to be in electrical communication with the first and second electrically conductive elements 2, 4. This step is carried out using an additive manufacturing technique, specifically rotary screen printing, using a roller 20.

Next, as shown in Fig. 2d, a transfer printing process 30 is used to arrange the third electrically conductive element 8 to be in electrical

communication with the force sensing element 6. First a stamp 22 is prepared by providing a stamp substrate 23 (made from polyester) and adding the third electrically conductive element 8 to the stamp substrate 23 (using a printing process). Next the stamp 22 is pressed into contact with the force sensor 1 and subsequently removed therefrom. The third electrically conductive element 8 is thus transferred to the force sensing element 6.

Fig. 2e shows the force sensor 1 at the end of the manufacturing process.

It will be understood that whilst each step of the method of manufacture has been carried out using a printing process, at least one of the steps of the method could be carried out using one or more additive manufacturing processes. For example, other manufacturing techniques, or processes, could be used to carry out the steps of the method, such as etching, lithography, and the like.

In addition to, or as an alternative to, the printing processes described above, any one of the printing processes could be a screen printing process, a flexography printing process, an offset printing process, an inkjet printing process, an aerosol printing process, a digital thermal transfer ribbon process, a thermal transfer printing process, a transfer printing process, a thermal transfer printing process, a digital printing process, a lamination printing process, an in-line printing process, and/or a printed circuit board printing process.

That is, it should be understood that each step of the method may be carried out using any one, or one or more, of the printing processes described herein.

In the embodiments illustrated and described here, the first and second electrically conductive elements 2, 4 are each provided from a conductive ink, and the third electrically conductive element 8 is provided from a resistive ink. The force sensing element 6 is provided from an anisotropic electrical conductivity ink.

It should be understood that the arrangement of the first, second and third electrically conductive elements 2, 4, 8 could be reversed. For example, the first and second electrically conductive elements 2, 4, could be added to the force sensing element 6 using a transfer printing process.

An advantage of the present invention is that the force sensor 1 will not transition from the off state to the on state when it is rolled or bent. That is, the force sensor 1 requires active pressure to be applied before it is switched on. Without wishing to be bound by theory, this allows the present invention to be integrated within a 3D surface, or within a flexible, foldable or bendable mobile phone display. For example, the force sensor 1 of the present invention, at least in some embodiments, can be rolled to a diameter of approximately 1 mm without being turned on.

Modifications may be made to the foregoing embodiments without departing from the scope of the invention. For example, the force sensor 1 may comprise one or more substrates 10.

Whilst in the embodiments illustrated and described here, the force sensor 1 is a stacked structure in which each layer is in conformal contact with each other layer, it should be understood that in other embodiments only some of the layers need be in conformal contact. For example, the first electrically conductive element 2 could be arranged to be in conformal contact with the first region 6a of the force sensing element 6. The second electrically conductive element 4 could be arranged to be in conformal contact with the second region 6b of the force sensing element 6. The third electrically conductive element 8 could be arranged to be in conformal contact with the third region 6c of the force sensing element 6. The first, second, and/or third electrically conductive elements 2, 4, 8 and/or the force sensing element 6 could be arranged to be in conformal contact with the, or each, substrate 10.

The force sensing element 6 could be configured such that the discrete conducting elements are not arranged to form an electrical current flow path at the first, rest position 14a, and are arranged to form an electrical current flow path at the second, deformed position 14b.

When the force sensor 1 is to be included within an optical display, or other optical component, at least a part of the first, second and/or third electrically conductive elements 2, 4, 8 and/or the force sensing element, and/or the substrate 10 may be configured to permit electromagnetic radiation in the visible wavelengths to pass therethrough.

In some embodiments, the first electrically conductive element 2 and the force sensing element 6 may be configured such that the electrical contact resistance therebetween is variable between a first value at the first, rest position 14a and a second value at the second deformed position 14b.

The first value could be higher than the second value. In this

arrangement, the contact resistance between the first electrically conductive element 2 and the force sensing element 6 can vary between a relatively high value at the first, rest position 14a, and a relatively low value at the second, deformed position 14b. Thus, the first electrically conductive element 2 and the force sensing element 6 are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element 6. The second electrically conductive element 4 and the force sensing element 6 may be configured such that the electrical contact resistance therebetween is variable between a first value at the first, rest position 14a and a second value at the second, deformed position 14b. The first value may be higher than the second value. In this arrangement, the contact resistance between the second electrically conductive element 4 and the force sensing element 6 can vary between a relatively high value at the first, rest position 14a, and a relatively low value at the second, deformed position 14b. Thus, the second electrically conductive element 4 and the force sensing element 6 are, in this arrangement, configured to have an electrical contact resistance therebetween that varies with the force applied to the force sensing element 6.

Whilst in the embodiments illustrated and described here, the first, second and third electrically conductive elements are depicted with a rectangular cross-section, it should be appreciated that the first, second and/or third electrically conductive elements could have other shapes of cross section. For example, the first, second and/or third electrically conductive elements could have a substantially semi-circular, elliptical, circular, and/or square cross section.