Electrically controlled elasticity utilizing piezoelectric coupling

Abstract

Electrical control of elasticity was performed in piezoelectric polymer films by connecting an electric circuit parallel to the sample electrodes. A polyvinylidene fluoride film and a vinylidene fluoride tetrafluoroethylene copolymer (73/27) film were used. Electrical circuits acting as a variable negative capacitor or a variable inductor were constructed using operational amplifiers. Theoretically, when the value of the external negative capacitance is increased, the observed elastic constant increases from that at an open circuit to positive infinity at around the value of the sample, turns to negative infinity, and then increases through zero to that at a short circuit. If the inductance of the external circuit is changed around the electrical resonant frequency, the elastic constant exhibits resonance and antiresonance against frequency. Experimental observations of the characteristics of the dynamic elastic constant agreed well with these theoretical predictions. By coupling the negative capacitance, the elastic constant changed between 0.5 and 2 times the original value, and the elastic loss increased to tan δ=0.7. © 2000 American Institute of Physics.