Giant piezoresistivity of nanocomposites with the tunnel conductivity

Insulating nanocomposite - metal granules in the rubbery polymer matrix of a low bulk compression modulus K - is a medium with the giant piezoresistivity: its conductivity σ(P) depends rather strongly on the pressure P. It is the consequence of the exponentially strong dependence of the tunnel electron intergrain transition probability on the distance between granules. Optimal systems are those with granules of the diameter ∼10 nm whose volume fraction equals 0.25-0.3. In that case one could expect the piezoresistive gauge factor G=[Δσ(P)/σ(0)](K/P) would be strongly nonlinear function of the pressure P and G∼105 at P≈0.8K, in comparison to G∼102 for typical bulk materials.