Abstract
Structures in nature have evolved to combine hard and soft materials in precise 3D arrangements, which imbues bulk properties and functionality that remain elusive to mimic synthetically. However, the potential for biomimetic analogs to seamlessly interface hard materials with soft surfaces for applications ranging from soft robotics and sealants to medical devices (e.g., prosthetics and wearable health monitors) has driven the demand for innovative chemistries and manufacturing approaches. Herein, we unveil a liquid resin for rapid, high resolution digital light processing (DLP) 3D printing of multimaterial objects with an unprecedented combination of strength, elasticity, and stability. Two enabling discoveries are the use of a covalently bound (hybrid) epoxy-acrylate monomer that precludes plasticization of soft domains and a wavelength-selective photosensitizer that greatly accelerates cationic curing for hard domains. Using dual projection for multicolor (UV and violet light) DLP 3D printing, several bioinspired metamaterial structures are produced, including those with a brick-and-mortar architecture to tune toughness, hard springs in a soft cylinder to tune compressive behavior, and a detailed knee joint with “bones” and “ligaments” to provide smooth motion.