Hybrid epoxy-acrylate resins for wavelength-selective multimaterial 3D printing

Structures in nature combine hard and soft materials in precise three-dimensional (3D) arrangements, imbuing bulk properties and functionalities that remain elusive to mimic synthetically. However, the potential for biomimetic analogues to seamlessly interface hard materials with soft interfaces has driven the demand for innovative chemistries and manufacturing approaches. Here, we report a liquid resin for rapid, high-resolution digital light processing (DLP) 3D printing of multimaterial objects with an unprecedented combination of strength, elasticity and resistance to ageing. A covalently bound hybrid epoxy-acrylate monomer precludes plasticization of soft domains, while a wavelength-selective photosensitizer accelerates cationic curing of hard domains. Using dual projection for multicolour DLP 3D printing, bioinspired metamaterial structures are fabricated, including hard springs embedded in a soft cylinder to adjust compressive behaviour and a detailed knee joint featuring 'bones' and 'ligaments' for smooth motion. Finally, a proof-of-concept device demonstrates selective stretching for electronics.