An Effect of a Needle Electrode for the Ohmic Contact Between an Electrode and Liquid Metal Droplet in Electrical Switching

Liquid metal, such as Galinstan, is deformable and flows so that liquid metal is attractive for applications in MEMS. Gallium based liquid metal, however, forms an oxide layer on its surface. Consequently, it is not easy to provide the ohmic contact between a counter electrode and liquid metal. Reported thickness of the oxide layer is 0.7nm. This paper presents a needle electrode for the counter electrode penetrating the surface oxide layer of liquid metal droplet on the counter electrode. Au needle electrodes with approximately $150\ \mu\mathrm{m}$ of height have been fabricated using wire-bonding technology. The diameter of the needle is $25\ \mu \mathrm{m}$. An effect of penetrating the oxide layer by the needle electrode has been confirmed. This paper reports switching of DC electrical signals as a promising application of the ohmic contact by liquid metal.