Gallium-based liquid metal inkjet printing

We report clog-free and oxide-free metal inkjet printing applicable to flexible electronics using gallium-based liquid metal alloy. Inkjet printing has been developed and expanded to make a pattern of either non-conductive or conductive materials. In order to print typical conductive material, it utilizes metal nanoparticle dispersed in solvent or melts the metal. However, those methods often encounters clogging and oxidation problem. We fabricated a simple polydimethylsiloxane (PDMS) based inkjet printer incorporated with hydrochloric acid (HCl)-impregnated paper as orifice material. A constant stream of gallium-based liquid metal alloy droplet was demonstrated using the inkjet printer. Depending on the applied flow rate, pinch off and Rayleigh instability phenomena were observed. We printed beads-on-string shape gallium-based liquid metal alloy line on various flexible substrates such as Si wafer, PDMS, and a paper. Finally, it was demonstrated that the inkjet-printed gallium-based liquid metal can maintain its line shape without disconnection even with the significant deformation of a flexible paper.