AC and DC behavior of finger-sensing metal/polymer composites at various pressures

The conductive composites of silicone filled with nickel were prepared, with a low percolation threshold of around 35 vol%. AC and DC conductivity of nickel/silicone composites with the filler content below or around percolation threshold were studied under uniaxial pressure. A pressure-induced percolation appeared at a very low pressure of finger-sensitive range (0.1–0.7 MPa) for each DC conductivity curve. The linear dependence of log σDC on p−1/3 at selected pressures proved the existence of tunneling mechanism and the potential barrier height for electron hopping in metal/polymer composite is strongly pressure dependent. The AC conductivity and the dielectric permittivity of the composite under different uniaxial pressures satisfies the universal dynamic power law, σAC ∝ ωx, ɛ ∝ ω−y, respectively. The critical exponents show that the frequency dependence of AC conductivity and dielectric permittivity of metal/polymer composite under various pressures could be well described by polarization effects.