Fully solution processed liquid metal features as highly conductive and ultrastretchable conductors

Liquid metal represents a highly conductive and inherently deformable conductor for the development of stretchable electronics. The widespread implementations of liquid metal towards functional sensors and circuits are currently hindered by the lack of a facile and scalable patterning approach. In this study, we report a fully solution-based process to generate patterned features of the liquid metal conductor. The entire process is carried out under ambient conditions and is generally compatible with various elastomeric substrates. The as-prepared liquid metal feature exhibits high resolution (100 μm), excellent electrical conductivity (4.15 × 104S cm−1), ultrahigh stretchability (1000% tensile strain), and mechanical durability. The practical suitability is demonstrated by the heterogeneous integration of light-emitting diode (LED) chips with liquid metal interconnects for a stretchable and wearable LED array. The solution-based technique reported here is the enabler for the facile patterning of liquid metal features at low cost, which may find a broad range of applications in emerging fields of epidermal sensors, wearable heaters, advanced prosthetics, and soft robotics.

Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

Harvesting body heat using thermoelectricity provides a promising path to realizing self-powered, wearable electronics that can achieve continuous, long-term, uninterrupted health monitoring. This paper reports a flexible thermoelectric generator (TEG) that provides efficient conversion of body heat to electrical energy. The device relies on a low thermal conductivity aerogel–silicone composite that secures and thermally isolates the individual semiconductor elements that are connected in series using stretchable eutectic gallium-indium (EGaIn) liquid metal interconnects. The composite consists of aerogel particulates mixed into polydimethylsiloxane (PDMS) providing as much as 50% reduction in the thermal conductivity of the silicone elastomer. Worn on the wrist, the flexible TEGs present output power density figures approaching 35 μWcm−2 at an air velocity of 1.2 ms−1, equivalent to walking speed. The results suggest that these flexible TEGs can serve as the main energy source for low-power wearable electronics.