MicroDLP: Microscope-Enabled Resolution-Switchable 3D Microprinting

Complex three-dimensional (3D) microarchitectures are increasingly important for microfluidics, microrobotics, organ-on-chip systems, biomedical devices, and architected materials. However, fabricating complex 3D microstructures with micrometre-scale precision remains a major manufacturing challenge. Integrating these fine features with larger supporting structures presents an additional challenge, requiring fabrication across multiple length scales within a single architecture. Although microscale 3D printing enables intricate geometries, the trade-off between resolution and build volume limits multiscale fabrication, while existing approaches often require complex optics and precise registration. Here, we introduce MicroDLP, a microscope-enabled digital light processing platform for versatile, resolution-switchable 3D microprinting. By integrating a projection module into a conventional inverted microscope, MicroDLP exploits its revolving objective turret to switch between 4x, 10x, and 20x objectives, providing projected pixel sizes from 1.89 to 0.378 um. We characterize photopolymerization, voxel geometry, and lateral feature resolution across magnifications to establish suitable microscale printing conditions. MicroDLP enables the fabrication of diverse and complex 3D microarchitectures, including freestanding trusses with 170 um struts, microvascular structures with 10 um features, interlocking gears, suspended microbridges, and microneedles with 3-5 um tips. Importantly, switching from 10x to 20x during fabrication produces monolithic 3D structures combining larger supporting foundations with fine micropillar arrays, without manual optical realignment. The shared optical pathway also enables coaxial in situ monitoring of photopolymerization. Together, these results establish MicroDLP as a versatile platform for microscale additive manufacturing, combining complex 3D microfabrication with resolution switching within a single monolithic structure.