A Flexible Capacitive Pressure Sensor Based on Thermoplastic Polyurethane Porous Films by Non-Solvent Induced Phase Separation

Flexible capacitive pressure sensors have received considerable attention due to their applications in wearable electronics. However, the complicated preparation process to get high performance limits their wide applications. We present a simple and cost-efficient method for flexible capacitive pressure sensors using thermoplastic polyurethane (TPU) porous films. The TPU and TPU/carbon black (CB) porous films, prepared by the non-solvent induced phase separation method (NIPS), were applied as dielectric layers and conductive layers of the high-performance capacitive pressure sensors. The obtained flexible capacitive sensor with double-layer structures exhibits excellent pressure sensing performance. Its sensitivity is 0.379 kPa $^{-{1}}$ in the range of 2.5–5 kPa and 0.215 kPa $^{-{1}}$ in the range of 5–12.5 kPa, respectively. Its repeatability and durability are also excellent under 1000 cycles. When pressure is applied to it for a short period of time, its capacitance change can always remain consistent within a certain error range. Furthermore, the sensors are verified for pressure-sensing mouse button that can better express the user's intention.