Multipath Projection\nStereolithography for Three-Dimensional\nPrinting Microfluidic Devices

Although many lab-on-chip applications require inch-sized\ndevices\nwith microscale feature resolution, achieving this via current 3D\nprinting methods remains challenging due to inherent trade-offs between\nprint resolution, design complexity, and build sizes. Inspired by\nmicroscopes that can switch objectives to achieve multiscale imaging,\nwe report a new optical printer coined multipath projection stereolithography\n(MPS) specifically designed for printing microfluidic devices. MPS\nis designed to switch between high-resolution (1× mode, ∼10\nμm) and low-resolution (3× mode, ∼30 μm) optical\npaths to generate centimeter-sized constructs (3 × 6 cm) with\na feature resolution of ∼10 μm. Illumination and projection\nsystems were designed, resin formulations were optimized, and slicing\nsoftware was integrated with hardware with the goal of ease of use.\nUsing a test case of micromixers, we show that user-defined CAD models\ncan be directly input to an automated slicing software to define printing\nof low-resolution features via the 3× mode with embedded microscale\nfins via 1× mode. A new computational model, validated using\nexperimental results, was used to simulate various fin designs, and\nexperiments were conducted to verify simulated mixing efficiencies.\nNew 3D out-of-plane micromixer designs were simulated and tested.\nTo show broad applications of MPS, multichambered chips and microfluidic\ndevices with microtraps were also printed. Overall, MPS can be a new\nfabrication tool to rapidly print a range of lab-on-chip applications.