Giant resistivity change induced by strain in a composite of conducting particles in an elastomer matrix

The piezoresistivity in a heterogeneous material formed by conducting nickel particles uniformly dispersed into a silicone-insulating matrix has been studied as a function of the filler content. A proper experimental apparatus was realized to investigate the direct dependence of resistivity on an uniaxial strain. In particular, when the volume fraction of the conductive charge approaches the conduction percolation threshold, at a proper value of the volume strain a little increment (2%) of the relative deformation can induce a transition from the insulating to conducting state accompanied by a giant resistivity change (about nine orders of magnitude). Some evidence that elastomer matrix properties contribute to determine both the peculiar development of the elasto-resistive coupling and its reversibility has been also found. The obtained results indicate the opportunity to optimize the investigated composite materials for the application as core of novel sensor devices governed by a threshold strain.