High-Resolution Patterning of Liquid Metal on Hydrogel for Flexible, Stretchable, and Self-Healing Electronics

Soft, wet, and biocompatible hydrogels have emerged as promising materials for flexible and stretchable electronics owing to their similar properties with biological tissues. However, most existing conductive materials used for hydrogel-based electronics have drawbacks such as poor biocompatibility, low conductivity, and/or high mechanical mismatch with soft hydrogels. In this work, direct patterning of nontoxic and highly conductive liquid metal (LM) on hydrogels is reported for soft and stretchable electronics without mechanical mismatches. The patterning is achieved by coating LM dispersed with magnetic microparticles on the wet hydrogel surface using a magnet. High-resolution LM patterns with microscale linewidths can be created with the assistance of a shadow mask fabricated by in situ digital laser cutting. Mechanical and electrical self-healing are achieved simultaneously by taking advantage of the hydrogen bonds in the polyvinyl alcohol hydrogel network and the merging of LM. A few applications of LM-based hydrogel electronics for wearable sensing, flexible wireless communication, and soft actuating are also demonstrated.