Overcoming Conductivity-Stretchability Tradeoff in Soft Conductive Composites Through Liquid Metal Junctions

Soft conductive composites are significant components of soft and wearable electronics. Existing soft conductive composites encounter difficulties in attaining 10% of copper’s electrical conductivity whilst maintaining high stretchability meanwhile. In this work, a novel ‘soft conductive junction’ concept is introduced to overcome the conductivity-stretchability tradeoff. This new paradigm of soft conductive composites consists of an interwoven copper fiber network embedded in a compliant elastomer matrix. The fiber junctions are connected using liquid metal bridge, which significantly lowers the junction resistance without influencing the stretchability of the fiber network. These hybrid composites uphold ultra-high and strain-insensitive conductivity that is around 60,000 S/cm under 55-75% stretch. Notably, the conductivity and stretchability of such composites can be tailored through prestrain. Potential applications of the composites in stretchable circuitry, wearable interconnects, capacitance tactile sensors, and highly stretchable Joule heaters are presented.