Multipath Projection Stereolithography for Three-Dimensional 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 trade-offs 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 multipath projection stereolithography (MPS) specifically designed for printing microfluidic devices. MPS is designed to switch between high-resolution (1× mode, ∼10 μm) and low-resolution (3× mode, ∼30 μm) optical paths to generate centimeter-sized constructs (3 × 6 cm) with a feature resolution of ∼10 μm. 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 that user-defined CAD models can be directly input to an automated slicing software to define printing of low-resolution features via the 3× mode with embedded microscale fins via 1× 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, multichambered 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.