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

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.