Strain sensor based on a flexible polyimide ionogel for application in high- and low-temperature environments

Ionogels possess an inherent conductivity, flexibility and outstanding mechanical properties. They have attracted increased attention because of their potential as mechanical transductors, flexible devices and artificial skins for modern electronics. However, the use of reported ionogels is limited to mild conditions with weak performance under thermal fluctuation. We prepared a novel polyimide ionogel by a facile one-step solvent displacement method using the ionic liquid (IL) [BMIm][BF4] to replace the native organic solvent in the polyimide organic gel. The resultant PI ionogel maintained excellent mechanical properties (tensile strength similar to 7.1 MPa and elongation at break similar to 320%), and high thermostability, and exhibited high ionic conductivity (1.9-5.2 mS cm(-1)) and a linear temperature dependence on conductivity. As a strain sensor, the polyimide ionogel provided high sensitivity, long-term durability and stability in a wide thermal range (-60 to 180 degrees C). The polyimide ionogels provide an opportunity for the preparation of stress sensors for high- and low-temperature applications.