Precisely Patterning Liquid Metal Microfibers Through Electrohydrodynamic Printing for Soft Conductive Composites and Electronics.

Liquid metal particle-based microfibers attract great interest in soft and wearable electronics. The most facile method to fabricate sub-50 µm liquid metal fiber is electrospinning. However, electrospinning has poor patterning ability and the electrospun fibers have inherent defects, which significantly lowers the electrical conductivity and limits their application. Therefore, better manufacturing methods are needed to precisely deposit high-quality liquid metal fibers. In this work, an electrohydrodynamic printing process is developed to precisely pattern liquid metal microfibers with minimal defects and ultra-high resolution (≈1.5 µm), overcoming the limitations of electrospinning. The patterned liquid metal fibers can be used for soft conductive composites and soft electronics with highly customized microscale features. The conductive composites embedded with these fibers not only exhibit high conductivity (up to 214 S cm), but also possess nearly strain-insensitive resistance (7.3% resistance change at 200% strain) and exceptional cyclic stability. Additionally, the potential applications of the liquid metal fibers and composites in soft sensors, stretchable heaters, and transparent electrodes are demonstrated.