Preparation of liquid metal circuits on flexible polymers by selective laser ablation: Essential mechanism of non-conductivity in ablation part

• Elucidating the mechanism of liquid metal lossing conductivity after laser ablation. • Making liquid metal circuits without additional molds (or stencils). • Making liquid metal circuits on a variety of flexible polymer substrates. • Exploring the applications in monitoring human motions. This work prepared liquid metal films by roll coating on various flexible substrates and then selectively ablated unwanted areas using near-infrared or ultraviolet lasers. The ablated regions lost their conductivity, while the remaining areas remained highly conductive, resulting in the successful fabrication of high-precision liquid metal circuits on various flexible and stretchable substrates. Mechanism of liquid metal lossing conductivity after laser ablation was investigated in detail. First, under the action of laser, most of Galinstan is evaporated. Second, although very small amounts of liquid metal still remain, they exist in isolated form and cannot form continuous conductive paths. Finally, a continuous porous network material appears in the residue after laser ablation, which is the non-conductive oxidation products of metallic gallium, indium, and tin. Due to the above three reasons, the liquid metal film after laser ablation can realize the transition from conductive to non-conductive, and the patterning of the liquid metal can be achieved. The application of liquid metal circuits prepared by this method in wearable sensors (electronic skin) was explored. This study contributes to the mechanism of selective laser ablation to fabricate liquid metal circuits, promoting a better understanding of this method in the field of flexible electronics.