Femtosecond laser preparing patternable liquid-metal-repellent surface for flexible electronics

Hypothesis: Controlling the wetting behaviour of gallium-based liquid metal is highly desired for soft electronics applications. Currently, achieving durable and patternable liquid-metal-repellent surfaces by a simple and flexible method is challenging. The femtosecond laser has a remarkable ability to modify the morphology and wettability of a solid surface. It can also potentially be applied to control the wettability of liquid metal and achieve complete liquid-metal patterns. Experiments: Femtosecond laser processing was used to form a microstructure on a polydimethylsiloxane (PDMS) surface. With regard to the laser-ablated surface, its morphology was observed by a scanning electron microscope, and its wettability to liquid metal was characterized by measuring the contact angle, sliding angle, and adhesive force. Finally, its potential applications in soft electronics were demonstrated. Findings: A layer of micro/nanostructures was directly prepared on the PDMS surface by laser ablation, presenting excellent liquid-metal repellence. Without expensive masks and complex operation processes, programmable liquid-metal-repellent patterns were easily obtained by femtosecond laser selectively treating the PDMS surface, enabling EGaIn to be patterned on the textured surface. The as-prepared liquid-metal patterns can be used as a flexible microheater and a microstrip patch antenna. It is believed that laser-patterned liquid-metal-repellent surfaces will have significant applications in soft electronics, such as antennas, microcircuits, lab on chips, and wearable electronic devices.