Response of P(VDF-TrFE) Sensor to Force and Temperature

Responses of a tactile sensor to force (0 to 9 N) and temperature (15 to 47 degrees C) are investigated. The sensor is based on ferroelectric polyvinylidene fluoride - trifluoroethylene (P(VDF-TrFE)) copolymer. The 2.5-mu m-thick copolymer layer was sandwiched between aluminum and gold electrodes and the active sensing area was 25 mm(2). The response of the sensor was measured in a form of capacitance recorded at 2 kHz. The capacitance was measured in a steady-state condition, i.e. after the force and temperature have stabilized. We have found that the sensor's sensitivity to temperature is comparable to that of force, and even greatly exceeds the force sensitivity when dealing with forces larger than 3 N. This is because the response of the sensor to temperature is approximately linear, while the response to the applied force is logarithmic. Consequently, at the lower end of applied forces (< 0.5 N), the sensitivity is 7.5 pF/N while the temperature sensitivity is about 7 pF/degrees C within the whole temperature range.