Pressure mapping using double layer dielectric system

The average value of surface density of the charge generated during contact electrification depends on the real contact area s. Because of finite elasticity and smoothness of contacting surfaces s value will depend on macroscopic pressure pM applied to the system. In a double layer system, containing elastic, foam like and solid-rigid layers s value may depend linearly on pM. In the case of dielectric-dielectric contacts the generated charge relaxes slowly, what may be used for "memorising" the surface charge and indirectly pressure distributions.