Field-Assisted Direct Patterning in Micro-Nano Structure of Liquid Metal with Self-Made Conducting Atomic Force Microscope

Abstract

Gallium-indium alloy is a kind of liquid metal and an important material in flexible circuits, wearable devices, micro-sensors and so on. Owing to its strong surface oxide film, it is difficult to process. Thus, fabricating the micro-nano structures with high repeatability and high precision has become a research focus in recent years. We propose a method of processing liquid metal with the aid of an electric field using a conducting atomic force microscope (CAFM) probe for the first time. The commercial self-sensing AFM probes were transformed into CAFM probes through micro-manipulation, and a set of low-cost and high-precision CAFM was designed and built. The liquid metal atoms were first coated on a CAFM tip and then, ionized and polarized when a threshold tip bias was achieved, thereby depositing onto the substrate. The patterning of liquid metal micro-nano structures was made by controlling the tip bias, the power-on time, and the moving speed of the probe. The manufacturing resolution of the structures reached 2μm, and the thickness was approximately 10-20 nm. The new fabrication strategy and the basic principle have a generalized purpose and are applied to nano-electronic devices, chip circuits, nano welding, and other fields.