Large-Scale Micropillar 3D Patterning with High-Aspect Ratio Using a Theta-Pipette

Meniscus-confined electrodeposition (MCED) has received widespread attention because of its simple physical construction and low economic cost. The matching of probe lifting rate and growth current in the MCED is the key to continuous and stable deposition. However, changes in the meniscus droplet morphology and surface evaporation will affect the stability deposition. Therefore, it is difficult to continuously fabricate high-aspect ratio array microstructures. This article proposes a novel electrodeposition physical model based on theta-pipette, and then proposes a closed-loop control method based on this model. The numerical analysis and experiment results demonstrate that 1) the deposition current decreases continuously with time using a constant voltage between electrodes for fabrication, which is easy to cause the fabrication to be interrupted; 2) adjusting the voltage between the electrodes in theta-pipette can approximately linearly adjust the deposition current, which can ensure stable fabrication. Finally, MCED process is controlled using a closed-loop control algorithm; a large-scale array (4 x 4) of micropillars with high-aspect ratio of 12:1 (the diameter 1.65 mu m and the height 21.4 mu m) has been stably fabricated. This approach can offer versatility and robustness for high-resolution 3D patterning at the microscale.