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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. Image 1 • A stretchable sensor array, which could work under either capacitance mode or TENG mode, enabling proximity, pressure and strain sensing, was developed. • The design of hollow micro-pillar microstructures enabled the E-skin to differentiate applied pressure from tensile strain. • The capacitance mode and TENG mode are complimentary to each other for pressure measurements as the capacitive mode is effective for high pressure range, while the TENG mode demonstrates high sensitivity at low pressure range. • The E-skin sensory array was integrated onto a bionic hand for actual tactile sensing during robotic operations. [ABSTRACT FROM AUTHOR]

Self-powered flexible sensors play an increasingly important role in wearable and even implantable electronic devices. Silk protein is an ideal material for flexible sensors because of its terrific biocompatibility and controllable degradation rate. Here, we overcome the problem of mechanical flexibility and poor electrical conductivity of proteins, and develop a highly transparent, biocompatible, full-degradable and flexible triboelectric nanogenerator (Bio-TENG) for energy harvesting and wireless sensing. First, the mechanical flexibility of the silk protein film is greatly enhanced by the mesoscopic functionalization of regenerated silk fibroin (RSF) via adding glycerol and polyurethane (PU). Second, hollow silver nanofibers are constructed on the silk film to form an air-permeable, stretchable, biocompatible and degradable thin layer and utilized as friction electrode. The obtained Bio-TENG demonstrates high transparency (83% by one Ag gird layer), stretchability (Ɛ = 520%) and an instantaneous peak power density of 0.8 W m−2 that can drive wearable electronics. Besides, the Bio-TENG can work as artificial electronic skin for touch/pressure perception, and also for wirelessly controlling Internet of Things as a switch. • Conductive and ultrastretchable (520%) silk protein film was prepared. • Hollow silver nanofibers were constructed on silk film to enhance conductivity. • Bio-TENG was air permeable, biocompatible, stretchable and degradable. • Bio-TENG was applied for energy harvesting and wirelessly controlling Internet of Things. [ABSTRACT FROM AUTHOR]