Epidermis of human skin: pyroelectric and piezoelectric sensor layer.

The epidermis of live human skin has a permanent electric dipole moment perpendicular to its surface. Voltage responses to a rapid change of temperature are pyroeletric, while voltage responses to pressure pulses are piezoelectric in nature. The time course of the responses depends on dX/dt (X, temperature or pressure). The epidermal surface can react to all physical environmental influences to which nonbiological pyroelectric materials are known to respond. Epidermal voltage signals can be perceived through the intraepidermal and the superficial dermal nervous network. The pyroelectric and piezoelectric properties are also measurable on dead, dry skin samples.