Self-packaged stretchable printed circuits with ligand-bound liquid metal particles in elastomer.

Packaging in stretchable electronics is crucial to protect components from environmental damage while preserving mechanical flexibility and providing electrical insulation. The conventional packaging process involves multiple steps that increase in complexity as the number of circuit layers multiply. In this study, we introduce a self-packaged stretchable printed circuit board enabled by the in situ phase separation of liquid metal particles (LMPs) within various polymer matrices during solution-based printing processes. The ligand-bound LMPs (LB-LMPs), engineered to inhibit oxide growth, undergo in situ sintering, prompting vertical phase separation. This synthesis strategy not only achieves high initial conductivity of the LMPs but also encapsulates them within the polymer matrix, preventing leakage and providing electrical insulation. Our method enables multi-layer circuit printing, eliminating the need for additional activation and packaging processes. Furthermore, by integrating conductive materials into packaging layers for selective electrical conductivity, vertical interconnect accesses and conductive pads can be formed, enabling large-scale, stretchable, and leakage-free multi-layer electrical circuits and bio-interfaces.