Nanofibrous Grids Assembled Orthogonally from Direct-Written Piezoelectric Fibers as Self-Powered Tactile Sensors

Tactile sensors are indispensable to wearable electronics, but still lack self-powering, high resolution, and flexibility. Herein, we present direct-written piezoelectric poly(vinylidene difluoride) fibers that are orthogonally assembled into nanofibrous grids (NFGs) as self-powered tactile sensors. Five nanofibrous strips (NFSs) are written on a polyurethane film via a uniform-field electrospinning (UFES) process, and two polyurethane films are orthogonally assembled into 5 × 5 NFGs with 25 pixels. Benefited from the mechanical flexibility and helical architecture of UFES fibers, stable piezoelectric outputs have been detected according to different locations or different pressures on an NFS, and a sensitivity of 7.1 mV/kPa is detected from the slope of voltage–pressure curves. In the orthogonally assembled NFGs, the pressure on a pixel of an NFS causes corresponding deformations of neighboring NFSs. The piezoelectric outputs vary with the distance from the pressing point, enabling us to position the pressing points and track the pressing trajectory in real time. Through judging piezoelectric outputs of all NFSs, precise locations of any pressed pixel with a resolution of 1 mm are presented vividly via luminous light-emitting diodes (LED), and the mapping profiles are displayed by pressing metal letters (S, W, J, T, and U) on multiple pixels. Furthermore, the coordinates of pressure either on an NFS or between NFSs with a resolution of 0.5 mm are reported digitally on a liquid crystal display (LCD). Thus, we developed novel self-powered tactile sensors with orthogonal NFGs to achieve real-time motion tracking, accurate spatial sensing, and location identification with high resolutions, which provide potential applications in electronic skin, robotics, and interface of artificial intelligence.