Adaptive Foam 3D Printing of Ultralight and Multifunctional Materials

Interest in the realm of soft materials toward low‐density yet mechanically robust products is evolving into a nascent field known as foam 3D printing, a compelling avenue for ultralightweight and multifunctional materials. Among an array of strategies, the combination of expandable microspheres (EMs) and 3D printing maps an adaptive, scalable, and versatile approach to generating cellular architectures with tunable properties. Herein, we feature an outlook of polymer foaming principles and various 3D printing techniques, followed by a comprehensive discussion on foam 3D printing via fused filament fabrication (FFF), direct ink writing (DIW), digital light processing (DLP), and inkjet printing. We critically elucidate recent advancements in the field, namely, the design of functionally graded foams, lightweight metamaterials, lattice‐reinforced panels, and multifunctional composites, culminating in an insightful perspective on this thriving field of research. Applications spanning energy absorption, thermal insulation, soft robotics, and wearable devices are highlighted to unveil the latent potential of printed foams. Our narrative will conclude through identifying key materials, processing, and product‐level hurdles and outlining promising areas for studying to expand the capabilities and impact of adaptive foam 3D printing in next‐gen materials and designs.