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.