Multipath projection stereolithography (MPS) for 3D printing microfluidic devices

Although many lab-on-chip applications require inch-sized devices with microscale feature resolution, achieving this via current 3D printing methods remains challenging due to inherent tradeoffs between print resolution, design complexity, and build sizes. Inspired by microscopes that can switch objectives to achieve multiscale imaging, we report a new optical printer coined as Multipath Projection Stereolithography (MPS) specifically designed for printing microfluidic devices. MPS is designed to switch between high-resolution (1xmode, [~]10{micro}m) and low-resolution (3x mode, [~]30{micro}m) optical paths to generate centimeter sized constructs (3cm x 6cm) with a feature resolution of [~]10{micro}m. Illumination and projection systems were designed, resin formulations were optimized, and slicing software was integrated with hardware with the goal of ease of use. Using a test-case of micromixers, we show user-defined CAD models can be directly input to an automated slicing software to define printing of low-resolution features via the 3x mode with embedded microscale fins via 1x mode. A new computational model, validated using experimental results, was used to simulate various fin designs and experiments were conducted to verify simulated mixing efficiencies. New 3D out-of-plane micromixer designs were simulated and tested. To show broad applications of MPS, multi-chambered chips and microfluidic devices with microtraps were also printed. Overall, MPS can be a new fabrication tool to rapidly print a range of lab-on-chip applications.