Piezoresistance of flexible tunneling-percolation networks

Abstract

We model changes in the conductivity of flexible composite films stressed by bending. By treating stress as a perturbation of the effective medium conductivity, we obtain an expression of the piezoresistance as a function of four material parameters. The model correctly predicts resistance spikes and their recovery under the action of viscoelastic forces, in good agreement with experimental observations over stress cycles. The theory may be used to design composite materials for high sensitivity touch sensors.

Graphite-polydimethylsiloxane composite strain sensors for in-situ structural health monitoring

“…They have derived a formula for the piezoresistance of a composite film under biaxial strain. Given the similar mechanical boundary conditions and similar PDMS parameters (Young's modulus, Poisson modulus, viscosity) to the present experiment, the piezoresistance formula [11] approximates well the response of the present sensors to uniaxial stains smaller than 1%. The good match of the theoretically predicted and experimentally observed piezoresistance has been demonstrated by Chauhan et al [10].…”

“…However Grimaldi and Balberg [30] have theoretically shown that a percolation threshold exists and that the network conductivity behaves similarly as a function of parameters as in conventional percolation. Taylor-Harrod et al [11] have further computed the conductivity of a viscoelastic tunnellingpercolation network which is highly relevant to the graphite-PDMS composite. They have derived a formula for the piezoresistance of a composite film under biaxial strain.…”

“…The piezoresistance formula [11] uses the four following parameters: the chemical affinity of graphite, the visco-elastic creep time, the incomplete stress relaxation ratio and the volume filling fraction of graphite nanoparticles in the host material. We used this theory to compute the calibration curve of piezoresistance in response to incremental strain steps.…”

“…Composite films that are sensitive to local strain [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] have recently been developed for making artificial skins [14][15][16][17][18]. These incorporate conductive nanomaterials that include graphite particles [10][11][12][13][14], graphite nanosheets [22], graphene flakes [20,21] or carbon nanotubes [15,19,24,25] in a flexible insulating matrix.…”

“…Composite films that are sensitive to local strain [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] have recently been developed for making artificial skins [14][15][16][17][18]. These incorporate conductive nanomaterials that include graphite particles [10][11][12][13][14], graphite nanosheets [22], graphene flakes [20,21] or carbon nanotubes [15,19,24,25] in a flexible insulating matrix. Addressable arrays with polydimethylsiloxane(PDMS)-based pixels have already been demonstrated to detect force fields with either current [18] or potential applications [19,23] in the development of electronic skins.…”