Fully flexible and mechanically robust tactile sensors containing core–shell structured fibrous piezoelectric mat as sensitive layer

Abstract

Tactile sensors based on poly(vinylidene fluoride) (PVDF) are widely investigated, but their flexibility and mechanical robustness are limited due to the poor elasticity of PVDF. Herein, fully flexible and mechanically robust tactile sensors with a sandwich-like structure are fabricated by introducing a core–shell structured fibrous piezoelectric mat between two fibrous TPU/AgNWs (TPU: thermoplastic polyurethane, AgNWs: silver nanowires) flexible electrodes. The piezoelectric mat works as the sensitive layer, in which TPU is designed as the elastic skeleton in the core of fibers to enhance the mechanical properties while PVDF is wrapped on TPU fiber as a piezoelectric component. The core–shell structured TPU/PVDF mat has achieved improved elasticity and stretchability and excellent piezoelectric effects are demonstrated (sensitivity: 95.8 mV N−1). Because of the flexibility of both sensitive layer and electrodes, the tactile sensors have achieved an elongation of 300 %, excellent elasticity, a sensitivity of 20.3 mV N−1 and stable sensing in more than 2,000 cycles. Interestingly, such tactile sensors also exhibit outstanding mechanical robustness and have the ability to properly respond to mechanical stimuli in deformed states. Various pressures generated in daily life (e.g., hand slapping, feather brushing, joint bending, blowing, vocal cord vibration and writing) are successfully monitored utilizing such tactile sensors. Overall, this work has provided a new clue to regulate the flexibility and mechanically robustness of tactile sensors.