Stretchable strain sensors based on polyaniline/thermoplastic polyurethane blends

Thermoplastic polyurethane/polyaniline-based stretchable strain sensors were prepared via in situ polymerization of aniline in the TPU solution in the form of thin films. The sensors where characterized for morphological and thermal properties, mechanical hysteresis and cyclic piezoelectric performance. Thermogravimetric analysis showed blends to be thermally stable up to 230 degrees C. Electrical conductivity increased up to 30 wt% of Ani.DBSA loading after which a decline was observed due to reduced conversion of aniline monomer to polyaniline. Piezo-resistive measurements also showed a decrease in electrical conductivity upon stretching due to disconnection mechanism between Ani.DBSA particles. The cyclic piezo-resistive properties were evaluated at a strain of 10%. The sensors showed a gauge factor of 2.59. The dispersion and distribution was uniform at all levels of Ani.DBSA loading as visualized by SEM analysis. Beside uniform dispersion, SEM analysis also revealed polyaniline chains connecting with the polyurethane matrix which increases its conductivity. Hence, the proposed sensors can be employed as flexible strain sensors.