BNT Scaffold Contributes to High-Performance Piezoelectric Composite Membranes for Self-Powered Flexible Pressure Sensors

Self-powered wearable piezoelectric sensors are a promising strategy for long-term health monitoring. Ceramic–polymer composite membranes are one of the most effective alternatives to achieve high-performance flexible piezoelectric materials. However, the unavoidable agglomeration of inorganic ceramic particles and the low solid content hinder further optimization of piezoelectric properties. In this work, we innovatively propose a process to fabricate flexible composite membranes exhibiting a high piezoelectric coefficient and permittivity through directly impregnating PDMS/Ecoflex (P/E) solution into a one-step sintered bismuth sodium titanate (BNT) porous scaffold. Compared with the prepared composite membranes by mixing BNT particles with P/E, the piezoelectric coefficient of our BNT scaffold/P/E membranes shows a 4.32-fold increase due to the interconnected porous scaffold providing perfect interfacial bonding and effective load transfer. By sandwiching the BNT scaffold/P/E composite membrane with flexible electrodes, we demonstrate a flexible self-powered pressure sensor for detecting dynamic pressure and a capacitive pressure sensor for static pressure measurement, both showing high sensitivity and great mechanical durability. Our work provides a routine for fabricating piezoelectric composite membranes with a high piezoelectric coefficient and permittivity.