Directed dielectrophoretic assembly and separation on microelectrodes patterned <i>via</i> stereolithography 3D-printed shadow masks

Microelectrode patterning is essential in lab-on-a-chip devices, facilitating electric field localization and thereby enabling advanced particle manipulation. Conventional photolithography, while precise, is both costly and complex for electrode patterning. As a cost-effective and accessible alternative, we employed stereolithography apparatus (SLA) 3D printing to fabricate shadow masks for use in microelectrode patterning. Using these SLA 3D-printed shadow masks, we successfully patterned gold microelectrodes with complex geometries. We demonstrated that precisely localized electric fields on the micro-patterned electrodes can direct dielectrophoretic assembly and separation of colloidal particles. These experimental results are further supported by analytical calculations and numerical simulations that elucidate frequency-dependent dynamic particle behavior in electric fields. Overall, our findings confirm that SLA 3D printing offers a practical, low-cost strategy for high-resolution microelectrode fabrication, with broad applicability in lab-on-a-chip systems, including biosensing, microfluidics, and nanodevice integration.