M.D. Dickey
North Carolina State University,
United States
Keywords: oxides, transparent conductive oxides, direct-write printing, dielectrics
Summary:
This talk will discuss efforts to take advantage of liquid metals to directly print both metallic and oxide thin films at ambient conditions. The metal is a gallium-based metal alloy that is a low-viscosity liquid at room temperature with low toxicity and negligible vapor pressure. Despite the large surface tension of the metal, it can be printed into non-spherical shapes due to the presence of an ultra-thin surface oxide skin. The ability to directly print liquid metal alloys into 3D structures enables soft, self-healing, and ultra-stretchable conductors. We recently discovered a way to separate the oxide from the liquid using fluid instabilities. The process works by dragging a meniscus of liquid metal across a surface. At the right conditions, the fluid inside the meniscus is unstable and only oxide is left behind on the surface. Doing so enables direct-write printing of very thin (~4 nm) oxides without the need for vacuum processing. Surprisingly, the oxide is conductive because the printing process deposits a bilayer film with a metallic interior. The ability to deposit oxide coatings is important for electronics, sensors, optics, and touch screens. This approach is appealing because it avoids vacuum processing that is typically used to deposit oxides.