US 6,543,299 B2 · Pressure measurement sensor with piezoresistive thread lattice

Abstract

A transducer sensor array for measuring forces or pressures exerted on a surface includes a lattice of individual force or pressure sensor transducer elements comprising intersecting regions of pairs of elongated, flexible threads, each consisting of a central electrically conductive wire core covered by a layer of piezoresistive material having an electrical resistivity which varies inversely with pressure exerted on the material. The threads are arranged into two parallel planar sets, one set forming parallel spaced apart rows and the other set forming parallel spaced apart columns angled with respect to the rows. Row and column piezoresistive threads are retained in physical contact with one another at cross-over intersection points forming a lattice of piezoresistive junctions comprising individual force sensing elements, either by being bonded between a pair of thin, flexible, upper and lower laminating sheets, or by being interwoven to form a fabric mesh. In either case, the sensor array formed by the piezoresistive threads has a highly flexible, fabric-like characteristic which enables the array to readily conform to irregularly curved object surfaces. External normal forces or pressures exerted on an upper surface of the array placed on an object surface causes the electrical resistance of piezoresistive junctions which are compressed in response to the external forces to vary in a predetermined way, enabling a two-dimensional plot of electrical resistance values of each junction node to be made, thus enabling a two-dimensional matrix or map of pressure values exerted on each point of a surface, overlain by the sensor array to be generated. In one embodiment, the piezoresistive layer covering each piezoresistive thread consists of an electrically conductive elastomer, such as silicone rubber impregnated with carbon particles. In another embodiment, the piezoresistive threads consist of a wire core spirally wrapped with a plurality of thin polymer filaments that have a relatively poor electrical conductivity, such as nylon fibers which have carburized outer surfaces.

Claims43

Dependent claims

A force sensing transducer for measuring external force exerted thereon, said transducer comprising;

d. at least a first, elongated flexible, electrically conductive thread, said thread having an elongated outer circumferential surface circumscribed by a first layer of piezoresistive material,
e. at least a second, elongated flexible, electrically conductive thread, said thread having an elongated outer circumferential surface circumscribed by a second layer of piezoresistive material and,
f. means for positioning said first and second threads with selected portions of said first and second piezoresistive layers in a mutually contactable relationship, whereby said external force is effective in pressing together said first and second piezoresistive layers together to thereby form a piezoresistive junction for arbitrary orientations and axial rotations of said first and second threads relative to one another, said junction having an electrical resistance which varies inversely in a predetermined way as a function of said external force.

A force sensing transducer array for measuring forces exerted on a surface, said array comprising;

a. a first plurality of elongated, flexible piezoresistive row threads disposed parallel to one another in a spaced apart disposition, each of said row threads comprising an elongated electrically conductive core having an outer circumferential surface circumscribed by a layer of piezoresistive material, said material having an electrical resistance which varies inversely in a predetermined way with force tending to compress said piezoresistive material,
b. a second plurality of column piezoresistive threads disposed parallel to one another and angled with respect to said row piezoresistive threads, each of said column piezoresistive threads comprising an elongated electrically conductive core having an outer circumferential surface circumscribed by a second layer of piezoresistive material, said material having an electrical resistance which varies inversely in a predetermined way with force tending to compress said piezoresistive material, and
c. retention means for holding said row and column piezoresistive threads angled with respect to one another to form a lattice of piezoresistive junctions at each of which said first piezoresistive layer of said second row thread contacts said second piezoresistive layer of a column thread, said junctions being formed independently of axial rotation angle of said row threads relative to said column threads, and axial rotation angles of a said column thereof relative to said row threads.

A force sensing transducer array for measuring forces exerted on a surface, said array comprising;

a. a first plurality of elongated, spaced apart, parallel, flexible electrically conductive row threads arranged in a first, row plane,
b. a second plurality of elongated, spaced apart, parallel, flexible electrically conductive column threads angled with respect to said row threads, said column threads arranged in a second, column plane parallel to said row plane, at least one of said row and column conductive threads including in combination an electrically conductive core having on an outer surface thereof a layer of piezoresistive material, said material having an electrical resistance which varies inversely in a predetermined way with force exerted thereon, said material electrically conductively contacting at least one of said column and row conductive threads at a plurality of contact regions to form thereat a plurality of piezoresistive junctions, said layer of piezoresistive material comprising a plurality of elongated resistive filaments made of a material having an electrical conductivity less than that of said conductive core, said filaments being gathered into at least a first bundle and wrapped around said conductive core in a spiral helix.

Dependencies are inferred from the claim text.

Pressure measurement sensor with piezoresistive thread lattice

Life of this patent

Pressure measurement sensor with piezoresistive thread lattice

Life of this patent

Abstract

Claims43