A micro-vibration-driven direct ink write printing method of gallium–indium alloys

Combining liquid fluidity and metallic conductivity, gallium–indium (Ga–In) alloys are making a splash in areas such as stretchable electronic circuits and wearable medical devices. Due to high flexibility, direct ink write printing is already widely employed for printing Ga–In alloys. Currently, pneumatic extrusion is the main method of direct ink write printing, but the oxide skin and low viscosity of the Ga–In alloys make it challenging to control after extrusion. This work proposed a method for direct ink write printing of Ga–In alloys utilizing micro-vibration-driven extrusion. Micro-vibration reduces the surface tension of Ga–In alloy droplets and avoids the appearance of random droplets during printing. Under micro-vibration, the nozzle tip pierces the oxide skin to form small droplets which have a high moldability. The droplet growth process is significantly slowed down by optimizing suitable micro-vibration parameters. Therefore, the Ga–In alloy droplets with high moldability can be maintained at the nozzle for a long period, which improves printability. Furthermore, better printing outcomes were obtained with micro-vibrations by choosing the proper nozzle height and printing speed. Experiment results demonstrated the superiority of the method in terms of Ga–In alloys extrusion control. With this method, the printability of the liquid metals is enhanced.