Multicolor Digital Light Processing 3D Printing Enables Dissolvable Supports for Freestanding and Non-Assembly Structures.

The limited diversity in photocurable resin chemistries has precluded access to certain geometries using digital light processing (DLP) 3D printing, a rapid, precise, economical, and low-waste manufacturing technology. Specifically, freestanding structures with floating overhangs (e.g., hooks) and mobile nonassembly structures that cannot be physically separated (e.g., joints) represent two such geometries that are difficult or impossible to access with contemporary DLP 3D printing. Herein, we disclose novel resins that selectively react with different colors of light to form soluble thermoplastics and insoluble thermosets. Systematic characterization of the acrylate- and epoxy-based resins and corresponding polymers from simultaneous UV and visible (violet or blue) light exposure revealed a rapid multimaterial 3D printing process (∼0.75 mm/min) capable of providing supports that dissolve in ethyl acetate, a "green" solvent, within 10 min at room temperature. Relative to manual support removal, the present process provides comparable or improved surface finishes and higher throughput. Finally, several proof-of-concept structures requiring dissolvable supports were 3D printed, including hooks, chains, and joints, which were scanned using computed tomography to showcase the process's geometric versatility and high fidelity. This work provides fundamental design principles for multimaterial resin chemistry and lays a foundation for automating next generation additive manufacturing.