Electrospun Ionic Nanofiber Membrane-Based Fast and Highly Sensitive Capacitive Pressure Sensor

Flexible pressure sensor has been widely used in different industries, but there are still some challenges for the fabrication of sensor with a superb sensitivity and large sensing range. In this paper, a flexible capacitive pressure sensor based on electrospun ionic nanofiber membrane is developed. The sensor contains an ionic nanofiber dielectric layer and two indium tin oxide polyethylene terephthalate (ITO-PET) films coated on the top and bottom of the dielectric layer, respectively. The electrical double capacitors are formed at the interface between the ionic nanofiber membrane and the electrodes. When external pressure is applied on the sensor, the distance between two electrodes decreases, which causes the increase of the ionization degree of ionic liquid as well as the effective contact area between the two electrodes and ionic nanofiber dielectric layer. Above changes lead to a rapid increase of the capacitance of the sensor. The sensing principles and the theoretical models of the sensor are systematically studied. Comparing to traditional capacitive pressure sensors, the developed sensor provides a high sensitivity up to 78.54 nF/kPa and a rapid dynamic response (16 ms) for pressure measurement. Experiments are also conducted to investigate the influence of the thickness and the bending radius of ionic nanofiber membrane as well as temperature and humidity of the environment.