Digitally-embroidered Liquid Metal Textiles for Near-field Wireless Body Sensor Networks

Clothing with electromagnetic functionalities can be used to interconnect a wireless network of battery-free sensors around the human body. Such smart clothing require textiles that are highly conductive, flexible, durable, and compatible with established manufacturing processes. Here, we demonstrate textiles with near-field functionalities fabricated by digital embroidery of liquid metal fibers. The liquid metal fibers, consisting of Galinstan in perfluoroalkoxy alkane tubing, exhibit mechanical flexibility comparable to the underlying materials and durability against mechanical bending (<1% electrical resistance variation on 10000 cycles), and high electrical conductance at radio-frequencies (~9.6 Ωm at 13.56 MHz). The digital embroidery process enables transfer of near-field inductive patterns optimized using full-wave electromagnetic simulations onto conventional textiles without blocking water vapour transport. We design and fabricate liquid metal fibers onto fabric skin patches for wireless power transfer at 13.56 MHz. Experiments show that the patches can conformally attach onto the surface of the body and provide robust wireless power transfer to devices in both wearable and implantable configurations during physical activity (<1.5% relative standard deviation during standing and running at 9.2 km/h), These results suggest the potential of liquid-metal based wireless systems to establish robust and unobtrusive wireless networks of battery-free wearable and implantable devices using near-field technologies.