Three Dimensional Microfabrication Using Local Electrophoretic Deposition Assisted with Laser Trapping Controlled by a Spatial Light Modulator

We describe a novel micro three-dimensional (3D) fabrication method based on electrophoretic deposition assisted by laser trapping. This method is a combination of laser trapping and electrophoresis deposition. In a colloidal nanoparticle solution, the nanoparticles are gathered into a laser spot focused on a substrate, they were then electrophoretically deposited on the substrate by applying an electrical field. Using the method, we have performed fabrication of micro 3D structures such as pillars and spirals by moving the substrate downward while keeping the deposition. In this paper, to improve the fabrication method, we introduced a spatial light modulator (SLM) into our system. The SLM can form multiple laser spots simultaneously to fabricate multiple pillars. However, in the case of fabrication of multiple microstructures using the multiple laser spots, unintended sub-spots also appear due to optical interference of the multiple laser spots, which results in deterioration of the fabrication. Here, to avoid the appearance of the undesirable sub-spots, a novel method using quasi-multiple laser spots were proposed. By switching a position of a single spot briefly using the SLM, multiple microstructures were successfully fabricated with suppressing the undesirable sub-spots. Furthermore, by oscillating a beam spot with a small amplitude while moving the substrate downward, we successfully improved the reproducibility of the fabrication.