Electrospun Spandex Nanofiber Webs with Ionic Liquid for Highly Sensitive, Low Hysteresis Piezocapacitive Sensor

Electrospun Spandex nanofiber webs having very high amount of nano-sized open cell can be used as a piezocapacitive sensor for monitoring both static and dynamic pressures due to excellent electrospinnability and very good elastic properties. Compared to our previously reported SBS and TPU electrospun nanoweb, Spandex showed relatively linear increase of capacitance with applied pressure and restored its initial thickness when the pressure was released due to the improved resilience and elasticity. Moreover, small amount of ionic liquid (IL) was added in Spandex dope solution to increase the sensitivity of sensor to pressure, which induced very large amount of capacitance change with pressure, as well as reducing the capacitance-pressure hysteresis. In this work, hysteresis of the sensor was assessed through measuring the capacitance values during 20 cyclic loading and unloading and was improved significantly from 7.5 % to 1.8 %. Creep and stress relaxation behaviors were also tested through measuring capacitance under the constant loading and loading under the constant capacitance as a function of time respectively, using a dynamic pressure tester and an LCR meter. The results are reported in detail.