Pressure Sensors Combining Porous Electrodes and Electrospun Nanofiber-Based Ionic Membranes

It is one of the most urgent development directions and crucial challenges for flexible pressure sensors to have both characteristics of high sensitivity and wide measuring range. To address this challenging problem, this paper proposes an innovative, convenient, and industrially scalable capacitive pressure sensor that combines porous electrodes and electrospun nano ionic membranes with surface microstructure. The advantage of this sensor is that nano ionic nanofiber membranes are directly prepared on porous conductive fabrics by electrospinning with high reliability and good repeatability. The prepared dielectric layer of the sensor is in complete contact with the electrode, which effectively eliminates the uncertainty of air gap interference in traditional packaging methods. The sensing mechanism of the designed sensor is also persuasively revealed by finite-element and theoretical analysis in this paper. First, the porosity of both the conductive fabric and dielectric layer expands the measurement range. Second, the surface microstructure of the nano ion membrane increases the effective contact area between the dielectric layers when external pressure is applied to the sensor, thus increasing the conduction path of the ions. The increase of the ionizing degree under pressure leads to the change of the interface capacitance. These make the sensor have high sensitivity in the wide measurement range. The designed sensor exhibits a sensitivity of up to 1254.5 kPa –1 over a low-pressure measurement range of 0–10 kPa, providing an amazingly wide measurement range of 0–800 kPa, with an extremely high sensitivity of 128.1 kPa –1 over the entire measurement range. The designed sensor illustrates both a fairly fast response time of 10 ms and a relaxation time of 16 ms, in addition to the durability of up to 3000 cycles. The above exceptional performance demonstrates its remarkable potential applications in smart wearable devices and pneumatic pressure monitoring.