Integrating digital light processing with direct ink writing for hybrid 3D printing of functional structures and devices

As an emerging branch of additive manufacturing, multi-material 3D printing has drawn tremendous attention as it offers more design flexibility that can combine materials with various mechanical, chemical, thermal-mechanical or electrical properties. However, low cost, high-speed, high-resolution, and versatile multi-material 3D printing methods are still lacking. In this paper, we present a new hybrid multi-material 3D printing system that consists of a top-down digital light processing (DLP) printing and a direct ink writing (DIW) printing to fabricate composite structures and unique devices in a single printing job. The vat photopolymerization-based DLP printing allows for high-speed and high-resolution printing of a material matrix with complex geometry. The material extrusion-based DIW printing enables the printing of functional material, including liquid crystal elastomers (LCEs) and conductive silver inks. With this hybrid 3D printing system, a wide choice of inks and resins can be used to print functional composites with tunable mechanical properties, enhanced interfacial bonding, and multifunctionality. We demonstrate that composites prototype, active soft robots, circuit-embedding architectures, and strain sensors can be successfully printed. This work provides a new and robust approach for 3D printing of multi-functional devices for broad applications in soft robotics, electronics, active metamaterials, and biomedical devices.