A stretchable dual-mode sensor array for multifunctional robotic electronic skin

A stretchable dual-mode sensor array is developed for applications as multifunctional robotic electronic skin (E-skin). The sensor array, fabricated with cross-grid liquid metal layers as electrodes separated by micro-structured dielectric layers, can act as E-skin sensors under either capacitance mode or triboelectric nanogenerator (TENG) mode. Under capacitance mode, the device can function as proximity sensors or pressure sensors, the design of the top and bottom electrodes geometry leads to optimized proximity sensing performances and the deliberate introduction of hollow micro-pillar microstructures in the dielectric layer enables the E-skin to differentiate applied pressure from tensile strain. Under TENG mode, the contact location and pressure can be determined by scanning the outputs from the top and bottom electrode arrays. The two modes are complimentary to each other for pressure measurements as the capacitive mode is effective for high pressure range (10–120 kPa), while the TENG mode demonstrates high sensitivity (highest 1.04 V/kPa) at low pressure range (<10 kPa). The sensor array is also implemented as E-skin in a bionic hand for tactile sensing.