Integration of Transparent Supercapacitors and Electrodes Using Nanostructured Metallic Glass Films for Wirelessly Rechargeable, Skin Heat Patches

Recent remarkable progress in skin-attachable devices has attracted substantial attention in various fields. Despite substantial improvement of their mechanical flexibility and stretchability for the comfort of individuals over the past decade, maximizing the transparency of these electronic tattoo is a much less explored area that is growing interesting as the invisible skin-attachable devices for user’s aesthetic satisfaction. In addition, their wireless operation on skin is another crucial factor to avoid interfering with the variety of user’s outdoor activities. Here, we demonstrate an unconventional fabrication of highly transparent supercapacitors and electrodes using random networks of nanostructured metallic glass nanotroughs for their integrations as wirelessly rechargeable and invisible, skin heat patches. Transparent supercapacitors (SCs) with fine conductive patterns were printed using an electrohydrodynamic (EHD) jet-printing. Also, transparent and stretchable electrodes, for wireless antennas, heaters and interconnects, were formed using random network based on nanostructured CuZr nanotroughs (CuZr NTs) and Ag nanowires (AgNWs) with superb optoelectronic properties (sheet resistance of 3.0 Ω/sq at transmittance of 91.1%). Their full integrations, as an invisible heat patch on skin, enabled the wireless recharge of supercapacitors and the functions of heaters for thermal therapy of skin tissue. The demonstration of this transparent thermotherapy patch to control the blood perfusion level and hydration rate of skin suggests a promising strategy toward next-generation wearable electronics.