A high κ, transparent, and stretchable Cu@TiO2 core@shell nanowire/poly(dimethylsiloxane) composite film for sensitive wearable touch sensor

Abstract

Touch sensors are crucial for the development of advanced wearable devices and enhancement of the user experience through human-machine interaction. The properties of dielectric films, including their high dielectric constants (high-κ), low loss tangents (tan⁡δ), transparency, and stretchability are key factors that impact the accuracy, reliability, and display visibility of wearable touch sensors. Here, we present an approach for fabricating a Poly(dimethylsiloxane) (PDMS)-based dielectric film that can achieve a dielectric constant 6 times larger than that of pure PDMS film by loading a very low wt% (3%) of copper@titanium dioxide (Cu@TiO2) core-shell nanowires (NWs) to PDMS matrix. TiO2 was deposited on surfaces of Cu NWs by a hydrothermal reaction to form the covering shell, and it is experimentally and theoretically proved that the shell can suppress the scattering from metal surfaces, resulting in improving the transparency, and reducing the dielectric loss of the film (tan⁡δ=0.01–0.06). The nanocomposite film also exhibits outstanding mechanical property (standing up to a tensile strain of 200%). The demonstration of a transparent, highly sensitive and low noise multi-touch sensor using high-κ film suggests that this film has potential application in next-generation of wearable electronic devices for human-machine interaction.