Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
  • G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
  • G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/205—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using distributed sensing elements

Definitions

• the present invention relates to a force sensing device, a method of manufacturing the force sensing device and a method of testing the force sensing device.
• a force sensing device comprising: a first conductive layer and a second conductive layer; a pressure sensitive active layer responsive to a mechanical interaction; and a force distribution structure positioned between said first conductive layer and said second conductive layer, said force distribution structure extending between a first end and a second end of said first conductive layer; wherein said force distribution structure is configured to expand the contact area between said pressure sensitive active layer and said first conductive layer in response to a force being applied to said force sensing device.
• a method of testing a force sensing device comprising the steps of: providing the force sensing device of any preceding claim; and applying an elastic actuator to a top surface of said first conductive layer to provide a mechanical interaction to said force sensing device.
• a method of manufacturing a force sensing device comprising the steps of: providing a first conductive layer and a second conductive layer; providing a pressure sensitive material responsive to a mechanical interaction between said first conductive layer and said second conductive layer; and positioning a force distribution structure between said first conductive layer and said second conductive layer such that said force distribution structure extends between a first end and a second end of said first conductive layer.
• Figure 1 shows an exploded schematic view of a force sensing device
• Figure 2 shows a schematic side view of the force sensing device of Figure 1 ;
• Figure 3 shows a method of testing the force sensing device shown in Figures 1 and 2 by means of an elastic actuator
• Figure 4 shows the application of a distributed force by means of the elastic actuator of Figure 3;
• Figure 5 shows an alternative force sensing device in a method of testing utilising a hemispherical probe;
• Figure 6 shows a substantially similar force sensing device to the force sensing device of Figure 5 in a method of testing utilising an elastic actuator
• Figure 7 shows an area-force curve illustrating the different dynamic responses of the embodiments shown in Figures 4,5 and 6;
• Figure 8 shows a logarithmic area-force curve corresponding to the embodiments of Figures 4,5 and 6.
• a force sensing device 101 comprises a first conductive layer 102 and a second conductive layer 103. Force sensing device 101 is further provided with a pressure sensitive active layer 104 which is responsive to a mechanical interaction and is positioned between conductive layer 102 and conductive layer 103. In Figure 1 , force sensing device 101 is shown in a schematic exploded view for illustrative purposes.
• conductive layer 102 and conductive layer 103 each comprise a conductive material.
• the conductive material comprises a metallic material such as silver-based printable ink or a carbonbased material such as a carbon-based printable ink. It is appreciated that, in an embodiment, the metallic materials of the first and second conductive layers may be substantially similar or substantially different.
• Pressure sensitive active layer 104 comprises a pressure sensitive material, and in an embodiment, the pressure sensitive material comprises a quantum tunnelling material. In an embodiment the pressure sensitive material comprises a printable ink. Examples of suitable materials can be obtained from the present applicant, Peratech Holdco Limited, Brompton-on-Swale, United Kingdom.
• Quantum tunnelling materials of this type are responsive to a mechanical interaction in that, when a force is applied, they exhibit a change in electrical resistance which can be used to measure the nature of the force applied. It is appreciated that other pressure sensitive materials may be utilised which also exhibit a change in resistance on application of an applied force.
• the layers of feree sensing device 101 are held in close proximity such that, when a mechanical interaction, such as a force or pressure, is applied to, for example, the top surface of conductive layer 102 in the direction of arrow 105, an electric current is transmitted through conductive layer 102 and active layer 104 to conductive layer 103.
• a mechanical interaction such as a force or pressure
• the conductive layers are held apart by the active layer and an electric current is not transmitted.
• the response to the mechanical interaction can be utilised to calculate the magnitude of the mechanical interaction and in some embodiments, the position of the mechanical interaction.
• force sensing device 101 is typically formed as a force sensing device having a substantially circular cross-section when viewed from above.
• force sensing device 101 may comprise an alternative cross-sectional area, such as a substantially square-shaped cross-sectional area.
• Pressure sensitive active layer 104 may comprise a plurality of feree sensing elements, thereby enabling the magnitude of an applied force in the direction of arrow 105 to be calculated.
• the dynamic range of force sensitivity of conventional force sensing devices of this type is in part dependent on a smooth increase in contact area between conductive layer 102 and conductive layer 103 with increase in force or pressure applied.
• the present invention aims to adapt these layers compared to conventional force sensing devices so as to optimise the increase in contact area between first and second conductive layers 102 and 103, thereby improving the dynamic range.
• force sensing device 101 further comprises a force distribution structure which is configured to extend an applied force across active layer 104, and expand the contact area between pressure sensitive active layer 104 and conductive layer 102 as will be described in further detail in Figures 2 to 4.
• Force sensing device 101 comprises conductive layer 102 and conductive layer 103 which are spaced apart by spacer gasket 201. Thus, between conductive layer 102 and conductive layer 103 is air gap 202 which maintains a space between conductive layer 102 and conductive layer 103.
• pressure sensitive active layer 104 Positioned between conductive layer 102 and conductive layer 103 is pressure sensitive active layer 104 and a force distribution structure 203 configured to extend a force applied across pressure sensitive active layer 104.
• Force distribution structure 203 is configured to expand the contact area between pressure sensitive active layer 104 and conductive layer 102 in response to a force, such as force 105, being applied to the force sensing device 101.
• force distribution structure 203 is not only positioned between conductive layer 102 and conductive layer 103, but also extends between a first end 204 and a second end 205 of conductive layer 102 thereby permitting expansion of the force and increasing across the whole of the layer and increasing the contact area between the conductive layer 102 and pressure sensitive active layer 104.
• FIG. 2 shows the force sensing device 101 in an uncompressed state in which a force or pressure has not been applied.
• force distribution structure 203 is retained between the two conductive layers in a rest configuration.
• force distribution structure comprises a substantially dome-shaped cross-section as shown. It is appreciated that alternative crosssections may be utilised that also allow for an applied force to be extended across pressure sensitive active layer 104. Thus, while a three-dimensional dome-shaped hemispherical cross-section is suitable in this case, alternatively dimensioned hemispherical cross-sections may be utilised along with other suitable shapes.
• force distribution structure 203 is axially symmetrical about a centre axis.
• Force distribution structure 203 also comprises a substantially rigid material.
• pressure sensitive active layer 104 is formed as part of the force distribution structure which comprises a pressure sensitive material applied over a solid three-dimensional structure.
• the pressure sensitive material may be applied to an upper surface of the force distribution structure 203 to form the pressure sensitive active layer 104.
• the pressure sensitive material may be printed over the substantially rigid material of force distribution structure 203.
• force distribution structure 203 itself is comprised of a pressure sensitive material which forms the entire structure.
• the force distribution structure 203 may be considered the pressure sensitive active layer 104 such that the force distribution structure can be considered to provide the pressure sensitive active layer.
• the pressure sensitive material comprises a quantum tunnelling material such as that previously identified as available from the present applicant, Peratech Holdco Limited.
• conductive layer 102 and conductive layer 103 each comprise a conductive ink which is printed onto a substrate.
• the substrate comprises polyethylene terephthalate (PET).
• a first substrate is provided and a conductive ink is printed onto the first substrate to produce conductive layer 102.
• a further substrate is then provided and a conductive ink is printed onto the second substrate to produce conductive layer 103.
• force sensing device 101 may be activated by the application of an elastic actuator 301 to a top surface 302 of conductive layer 102 to provide a mechanical interaction to force sensing device 101.
• This method of testing the force sensing device 101 simulates a pressure or force applied to force sensing device 101 which may take the form of a finger press of a user of a force sensing device or similar in accordance with the present invention.
• Figure 3 therefore shows the elastic actuator 301 positioned for an application of a force for transmission to force sensing device 101 to conductive layer 102, pressure sensitive active layer 104 and conductive layer 103.
• force sensing device is shown in an uncompressed state whereby a force is yet to be applied.
• a distributed force 401 is applied by means of elastic actuator 301 as shown in Figure 4 moving the force sensing device form the uncompressed state of Figure 3 to the compressed state of Figure 4.
• a force 401 is uniformly applied to upper surface 402 of conductive layer 102.
• This deforms conductive layer 102 which, due to the nature of the force distribution structure 302 is spread across a larger cross-sectional area of conductive layer 102. As indicated, this deforms conductive layer 102, however, the application of force is distributed across conductive layer 102 thereby altering the spread of force.
• Figure 5 illustrates a typical conventional set-up for a method of testing a force sensing device which typically gives a positive dynamic range for a force sensing device as used in real-world applications.
• Figure 5 shows a conventional force sensing device 501 comprising conductive layer 502 and conductive layer 503 which are spaced apart by means of a spacer gasket 504. Spacer gasket 504 separates conductive layers 502 and 503 and creates an air gap 505 therebetween.
• a hemispherical probe is shown to illustrate the effects on a force sensing device without a force distribution structure in which a force is applied 506 by means of hemispherical probe 507.
• force sensing device 501 is shown in a compressed state.
• the deformation of conductive layer 502 brings conductive layer 502 into contact with conductive layer 503 in the manner shown.
• Figure 6 shows a conventional set-up for a method of testing a force sensing device utilising an elastic actuator.
• a flat elastic actuator 601 is utilised to apply distributed force 602.
• the force sensing device 603 comprises a first conductive layer 604 and second conductive layer 605 which are spaced apart by means of a spacer gasket 606. Force sensing device 603 is shown in a compressed state.
• first conductive layer 604 in response to a force 602 from actuator 601 , brings conductive layer 604 into contact with conductive layer 605.
• Figure 7 shows an area-force curve illustrating the different dynamic responses of the embodiments shown in Figures 4, 5 and 6.
• Curve 701 corresponds to the embodiment and present invention of Figure 4.
• Curve 702 corresponds to the embodiment shown in Figure 5, and curve 703 corresponds to the embodiment shown in Figure 6.
• curve 702 which corresponds to the hemispherical probe 507 being used on a force sensing device not comprising a force distribution structure of the present invention.
• the areaforce response indicates that the contact area increases proportionally to the input force. In this way, as the probe applies a force, the first and second layers make initial contact which gradually expands outwards with deformation of the probe actuator 507.
• curve 701 can be produced which indicates a reasonable approximation of the probe response.
• the elastic actuator 301 applies distributed force 401 , the contact expands outwards conforming to force distribution structure 302. Consequently, the area-force dynamic range corresponds to the size of the increase in area for a given increase in force. This will be illustrated further in the corresponding logarithmic area-force curve in Figure 8.
• a logarithmic (log-io) area-force curve is shown in respect of Figure 8.
• Curve 801 corresponds to the embodiment of Figure 4
• curve 802 corresponds to the embodiment of Figure 5
• curve 803 corresponds to the embodiment of Figure 6.
• the logarithmic scale illustrates the area-force dynamic range and its relationship to the size of the increase in area for a given increase in force.
• curve 801 shows an increase in contact area 805 and curve 802 shows an increase in contact area 806.
• the force sensing device of the present invention therefore provides a force distribution structure within the force sensing device which simulates the force distribution of conventional structures.
• a dynamic range is achieved unlike in conventional procedures as illustrated by the example in Figure 6. This ensures a smooth gradual increase of the effective dynamic range thereby allowing for more sensitive readings to be taken and improve the sensitivity range of the force sensing device.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)

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• 2020
  • 2020-08-10 GB GBGB2012388.1A patent/GB202012388D0/en not_active Ceased
• 2021
  • 2021-08-09 KR KR1020237008353A patent/KR20230082013A/ko active Pending
  • 2021-08-09 JP JP2023509590A patent/JP2023541792A/ja active Pending
  • 2021-08-09 EP EP21765968.9A patent/EP4193134B1/en active Active
  • 2021-08-09 WO PCT/GB2021/000089 patent/WO2022034277A1/en not_active Ceased
  • 2021-08-09 CN CN202180069162.9A patent/CN116324358A/zh active Pending
• 2023
  • 2023-02-10 US US18/108,071 patent/US20230194366A1/en active Pending

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