Nowadays, stretchable/epidermal electronics based on liquid alloys has attracted more and more attention, and various processing techniques have subsequently been developed to demonstrate diverse applications never seen before. However, to fully exploit its potential advantages, epidermal electronics is still searching for a technique meeting all demands on resolution, pattern complexity, and operational flexibility. In this study, we propose a technique that allows for complex and high-density patterns on thin stretchable substrates by combining ultraviolet laser patterning of a modified water-soluble mask, atomized spray deposition of liquid alloys on a flexible temporary substrate, lift-off by water dissolving, and finally, component integration and encapsulation. With this new technique, it was possible to make epidermal precision strain sensors with liquid alloy patterns of high density, which were capable of monitoring fine local skin movements such as the detailed process of wrinkle formation as well as the overall motion of the body part. In addition, this process is highly efficient and well controllable, with high potential for possible industrial automation and massive production.
Keywords: epidermal strain sensor; laser patterning soluble mask; liquid alloy patterning; local strain sensor; skin movement; two-dimensional strain sensor.