Industrially-friendly rapid printing of stretchable liquid metal circuits for patch-mode wearable healthcare devices

Abstract

Gallium-based liquid metals stand out as promising candidate materials for constructing stretchable conductive paths in soft electronics, but they are limited by high-cost laboratorial means of processing and exhibit poor wettability with most substrates. Here, we demonstrate a rapid, economical and industrially-friendly pattern technology, sponge-roller assisted liquid metal printing (SALP), which divides, extracts, transfers and integrates liquid metal droplets for patterning by its 3D grid structure and external pressure. SALP also provides universal high-adhesion by selective regulation of Ga₂O₃. High resolution (<50 μm) and low resistance change stretchable circuits could be realized by SALP under a prestretched platform. In addition, a stretchable reflectance oximeter patch composed of SALP-prepared circuits and rigid sensors is fabricated to monitor oxygen saturation and heart rate by sticking to fingertips, wrists and earlobes. This indicates that SALP technology is very competitive for industrial high-throughput fabrication of stretchable circuit boards.