Rapid 3D micro-fabrication using freestanding hybrid mask-assisted electrospray

Abstract Micro-fabrication techniques are of great interest to many researchers owing to their high precision and design variability over large-area substrates. However, it often requires complicated, time-consuming, and costly processes, such as fabrication and etching for a high-resolution photo-resist mask. Herein, we propose a rapid 3D micro-fabrication technique that utilises a reusable freestanding hybrid mask-assisted electrospray technique. The highly convergent electric field created by the hybrid mask was embedded into an electrospray system to focus the charged Ag-NPs and form a micro-scale 3D structure with high efficiency. Numerical simulations and parametric studies were conducted. It is evident that the mask metallic layer dominates the generation of a highly convergent electric field, and the repulsive force provided by the insulating layer could prevent mask contamination. The final pattern resolution and aspect ratio could be effectively manipulated by controlling the mask voltage and deposition duration. The fabrication of a 3D structure with a height of 45 μ m and an aspect ratio exceeding 3 only requires a deposition duration of approximately 60 s. The pattern resolution was 10 μ m and the size ratio was less than 0.01. Furthermore, this technique has been applied to the fabrication of micro-scale heat sinks for thermal management in electronic devices.