Breaking the 100 µm Barrier: Sub-10 µm 3D Microfluidic Channels via Low-Cost Maskless Photolithography

Rapid prototyping of microfluidic devices-enabling the swift and cost-effective translation of digital designs into functional components-remains a critical challenge in the field. While vat photopolymerization offers many advantages over soft lithography for microfluidic fabrication, over-curing caused by light penetration in liquid resins frequently leads to microchannel blockages, limiting achievable channel dimensions. In this work, a modular, maskless photolithography approach using a digital micromirror device (DMD) is presented to regionally photocure resin between prefabricated rigid substrates and covers. This method eliminates the need to print a separate sealing layer, allowing the fabrication of microchannels with widths as small as a single DMD pixel and heights below 10 µm-significantly surpassing the >100 µm height limitation of conventional 3D photopolymerization techniques. Adjustable substrate selection and the ability to integrate various resins support smooth transitions from 2D to complex 3D microfluidic architectures through straightforward layer stacking, while also allowing customization of optical, electrical, and chemical properties. The low cost (under $250), high precision, and rapid device preparation offered by this method provide a compelling alternative for fabricating advanced microfluidic systems, thereby expanding the field's capacity for innovative device design and application.