Multimaterial 3D Printing for Soft Robotics Applications

3D printing (additive manufacturing, AM) where materials are deposited in a layer-by-layer manner to form a 3D solid has seen significant advances in the recent decades. 3D printing has the advantage in creating a part with complex geometry from a digit file, making them an idea candidate for making architected materials. Multimaterial 3D printing is an emerging field in recent years in AM. It offers the advantage of placement of materials with different properties in the 3D space with high resolution, or controllable heterogeneity, making them particularly attractive for robotics applications. However, developing multimaterial 3D printing is also challenging because of the difference in processing conditions for different materials. In this talk, we present our recent work in developing multimaterial AM methods. In the first approach, we present a new development where we integrate two AM methods, direct-ink-write (DIW) and digit light processing (DLP) into one system. In this system, the DLP prints complex bulk parts while DIW adds functional inks, such as conductive materials or liquid crystal elastomers. In the second approach, we recently developed a grayscale DLP (g-DLP) 3D printing method and rationally design polymer resin where we can print a monolithic part with a large property gradient, such as a modulus contrast of more than 30,000 times. We further explore how to use these multimaterial 3D printing techniques to fabricate shape morphing structures, including direct 4D printing of 2D lattice structures, lattice structures with changing shape driven by liquid crystal elastomers, and 3D lattice structures by gradient materials. We also demonstrate how these new printing methods can used for soft robotic applications.