Rapid-Response, Low Detection Limit, and High-Sensitivity Capacitive Flexible Tactile Sensor Based on Three-Dimensional Porous Dielectric Layer for Wearable Electronic Skin.

Three-dimensional (3D) porous conductive composites explored in highly sensitive tactile sensors have attracted extensive close attention in recent years owing to its peculiar porous structure and unique physical properties in terms of excellent mechanical flexibility, high relative dielectric permittivity, and good elastic property. Herein, we report an practical, efficient, and macroscopic dip-coating process to manufacture rapid-response, low detection limit, and high-sensitivity highly sensitive capacitive flexible tactile sensors. The fabrication process, tactile perception mechanism, and sensing performances of the developed devices are comparatively investigated. The homogeneous 3D hybrid network constructed by graphene nanoplatelets (GNPs)/carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs)/silicone rubber (SR) composite anchored on polyurethane sponge (PS) skeletons exhibits a significantly improved dielectric property, resulting in high-performance capacitive flexible tactile sensor with fast response time (~45 ms), extremely low-pressure detection limit of ~3 Pa and excellent sensitivity (~0.062 kPa-1), and the excellent durability and stability over 2000 cycles. Importantly, the flexible devices can be used as the wearable electronic skin and successfully mounted on human skin or soft-bodied robot to achieve the capability of physiological stimuli monitoring, micro-pressure monitoring and soft grabbing, etc. Our rapid-response, low detection limit, and high-sensitivity capacitive flexible tactile sensor with novel 3D porous dielectric layer could be a prospective candidate for the wearable applications in real-time and high accuracy portable healthcare monitoring devices, advanced human-machine interface, and intelligent robot perception systems.