Multi-Material DLP via Stacked Dissimilar Resins toward Bioinspired Water Nucleation

Abstract

Multi-material vat photopolymerization has the potential to overcome drawbacks of existing 3D printing techniques. Complex heterogenous structures, particularly those found in nature, are uniquely optimized and require research into manufacturing techniques to emulate. Additive manufacturing has accelerated modeling of bioinspired architectures, but current methods have faced accessibility challenges due to process complexity, limited material properties, or slow speeds. A simpler technique, Layered Printing, involves stacking resins in a single vat and printing in one step. However, the method remains largely unexplored because of inherent cross-contamination during printing. To reduce this constraint, we designed stacked resins to have limited miscibility via contrasting density, viscosity, and hydrophobicity, and to produce polymers with widely different stiffness (i.e., 50 vs 1000 MPa) and wettability (e.g., contact angles of 60° vs 107°). We characterized the interface of the printed polymers via mechanical and chemical techniques, revealing a region that appears relatively sharp to the naked eye but more graded at the microscale. The multi-material function of Layered Printing was demonstrated by mimicking the fog-collecting architecture of a desert beetle, which relies on hydrophobic and hydrophilic regions to nucleate water droplets in low moisture conditions.