Hydrophobic, Structure-Tunable Cu Nanowire@Graphene Core-Shell Aerogels for Piezoresistive Pressure Sensing

Copper nanowires (CuNWs) are highly conductive yet low-cost nanostructures for constructing piezoresistive pressure sensors. Rational design and controllable fabrication are essential steps toward high-performance CuNW-based sensors, and the oxidation tendency of CuNWs must be inhibited. Conducting and flexible CuNW@graphene (CuNW@G) core-shell aerogels are fabricated with tunable microstructures via a simple assembly followed by thermal annealing, in which the aerogel bulk density, surface wettability, Young's modulus, and electrical conductivity can be adjusted accordingly by varying the initial CuNW dispersion concentration. In particular, these core-shell aerogels convert from hydrophobic to superhydrophobic at higher CuNW concentration with reduced adhesion to water. In the range of investigated CuNW dispersion concentration, the chemical constituent and structure of as-produced graphene shell is nearly the same, as is the aerogel's antioxidation stability. Based on the piezoresistivity of the core-shell aerogels, flexible pressure sensors operated at a bias voltage of 0.1 V are demonstrated, which can detect compressive stress as low as 640 Pa and exhibit fast response time less than 16 ms. Furthermore, polydimethylsiloxane-encapsulated CuNW@G aerogels show an enhanced response and higher reversibility. A general and scalable strategy for developing aerogel-typed piezoresistive pressure sensors with stable performance and low cost is presented.