Reciprocity failure in piezoelectric polymer composite

Reciprocity principles, which entail equivalent outcome on exchange of cause and effect, are widely used and accepted. We present a piezoelectric composite system designed so that reciprocity does not hold; sensitivity is substantially enhanced. Reciprocity failure is observed in which the piezoelectric direct effect (stress causes polarization) sensitivity d(kij)(d) is unequal to the converse effect (electric field causes deformation) sensitivity d(kij)(c). The piezoelectric polymer PVDF under isothermal conditions on a polymer substrate obeys reciprocity. Reciprocity failure occurs when a bumpy contact condition causes stress gradients. Reciprocity failure with strong frequency dependence occurs in the presence of thermal flux that is modulated by force: a non-equilibrium condition. Non-reciprocal effects give rise to a maximum enhancement of a factor of five in sensitivity.