Ultra-sensitive, fast response microcapsule structure capacitive sensor with encapsulated columnar nano-ZnO for electronic skin

Abstract

The capacitive pressure sensor holds broad prospects in medical devices and electronic skins. However, challenges persist in enhancing the stability of its capacitance and its response/relaxation time. To tackle these issues, we have proposed a highly sensitive capacitive sensor based on polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) with a microcapsule structure coated with nano-ZnO. The sensor integrates a semiconductor filler within a porous microstructure, enabling it to be positioned within the matrix’s pores for the purpose of monitoring human health. This P(VDF-TrFE)-ZnO dielectric layer with a short rod-like ZnO particle-in-micropore (SRP-MP) structure effectively enhances the structural stability and capacitance change rate of the dielectric layer. It boasts an ultrahigh sensitivity of 3.1 kPa^-1, a broad pressure range of up to 50 kPa, an ultra-low relaxation response time of 23 ms, and the ability to detect an ultra-low minimum pressure of 50 Pa. The sensor’s structural stability has been significantly improved, and it has demonstrated excellent fatigue resistance in 10,000 cycles tests. Following this, we delved into the sensor’s sensing mechanism. To elucidate the reasons behind the sensor’s enhanced performance, we modeled its interior and conducted finite element analysis simulations (COMSOL) to investigate its internal sensing mechanism and piezoelectric response. Finally, we conducted various tests on the sensor’s human application to clarify its performance in actual situations, demonstrating significant application potential.