The use of complex impedance spectroscopy measurements for improving strain sensor performance

Abstract

Ultrasensitive strain sensors have significant practical application in human-motion detection. However, there is still a challenge for developing strain sensors that are capable of detecting high strain and a high gauge factor (GF). The aim of this study was to investigate whether a semiconducting polymer and AC measurements are able to improve the GF of stretchable sensors. We employed complex impedance spectroscopy measurements to adjust the optimal operating frequency and the impedance component for improving the device performance of a polyaniline film on a flexible poly(vinyl chloride):diisononyl phthalate sub-strate. In the DC regime, the sensor revealed linearity and GF ∼18 at 46% strain. oreover, the frequency of 100 Hz corresponds to the ideal work re- gion to operate the device that unifies sensitivity and linearity, as well as to directly correlate GF and Z∗(100) data. The most surprising correlation is with GF from Z”(100), i.e. GF”(100), which is about 9 times higher than GF (DC regime) at 46% strain. The Cole-Davidson approach is developed, in which Z’(f) and Z”(f) are calculated as functions of tensile stress. This model provides the correlation between GF”(100) and the electrical resistance and capacitance of the device, as well as the charge-carrier hopping distance dependence on the tensile stress.