A Thermally Expandable Resin for the Volumetric Additive Manufacturing of Shape‐Memory Functional Foams

Abstract Tomographic Volumetric Additive Manufacturing (TVAM) is a 3D printing technique that produces parts extremely fast by projecting 2D images into a rotating vial of resin, printing the structures all at once, instead of layer‐by‐layer like in traditional 3D printing. So far, print sizes are limited by the size of the resin vial and most materials developed for TVAM are fully dense at around 1 g cm −3 . Development of novel materials for TVAM is challenging, as tailored viscosity and optical properties are required. Here an expandable foaming resin compatible with TVAM is presented, which undergoes thermally‐initiated expansion. With this material, printing parts with sizes exceeding the resin vial becomes possible. Several printed and foamed structures are shown and their characterization, with foamed parts reaching densities as low as 0.16 g cm −3 and volumetric expansion ratios of 500%. The foamed parts also show shape‐memory properties, with which a thermally activated gripping device is produced that grasps objects when warmed above its glass transition temperature. This foaming resin introduces a new category of materials to TVAM, enabling for the first time the rapid printing of lightweight, reprogrammable multi‐cm structures without changing vial size or the complexity of the TVAM print system.