Electrohydrodynamic (EHD) Printing of Molten Metal Ink for Flexible and Stretchable Conductor with Self‐Healing Capability

Abstract Direct printing of flexible and stretchable conductors provides a low‐cost mask‐less approach for the fabrication of next‐generation electronics. In this work, an electrohydrodynamic (EHD) printing technology is studied to achieve high‐resolution printing of low‐melting‐point metal alloys, which enables low‐cost direct fabrication of metallic conductors with sub 50 µm resolution. The EHD printed microscale metallic conductors represent a promising way to create conductive paths with metallic conductivity and excellent flexibility and stretchability. A stable electrical response is achieved after hundreds of bending cycles and during stretching/releasing cycles in a large range of tensile strain (0–70%) for the printed conductors with properly designed 2D patterns. Due to the low melting point of the metal alloy ink, the printed conductor demonstrates self‐healing capability that recovers from failure simply by heating the device above the eutectic temperature of the metal ink and applying slight pressure. A high‐density touch sensor array is fabricated to demonstrate the high‐resolution capability of the EHD printing for the direction fabrication of flexible and stretchable devices.