Cu–Ag core–shell nanowires for electronic skin with a petal molded microstructure

Abstract

Flexible electronic skin (e-skin) has been widely researched due to its potential applications in wearable electronics, robotic systems, biomedicine, etc. For realization of lower cost e-skin, copper nanowires (CuNWs) often serve as conductive fillers because of their high conductivity and flexibility. However, CuNWs are very sensitive to oxygen which greatly hinders their development. To solve this issue, a facile galvanic replacement reaction without any heating, stirring or dispersant was performed to coat a thin layer of silver (20 nm) on the surface of CuNWs, and Cu–Ag core–shell nanowires (Cu–Ag NWs) with excellent oxidation resistance were obtained and were used as conductive fillers for e-skin. To further increase the sensitivity and reduce the response time and detection limit, the micro-structure of the surface of the rose petal was replicated and introduced onto the 2D polydimethylsiloxane (PDMS) surface. The bio-inspired piezoresistive e-skin demonstrates high sensitivity (1.35 kPa⁻¹), very low detection limit (<2 Pa), very low response time and relaxation time (36 ms and 30 ms) and outstanding working stability (more than 5000 cycles). The high performance e-skin has extensive applications in voice recognition, wrist pulse monitoring and detection of spatial distribution of pressure.