Lightweight reusable energy-absorbing multiscale structures by polymerization-induced phase separation in 3D printing

Conventional energy-absorbing materials dissipate energy primarily through irreversible mechanisms such as plastic deformation, which often makes them single-use. To achieve reusability, energy-absorbing architectures relying on snap-through buckling or friction have been explored, but they typically require finely tuned geometries and additional design complexity that adds dead weight and complicates manufacturing. Here we introduce elasticity-assisted self-healing engineered structures (EASEs), a class of 3D-printed hybrid polymers that combine high specific energy absorption (SEA) with strong recoverability of mechanical performance after severe damage. The material comprises self-healable glassy epoxy domains dispersed within a rubbery polyurethane acrylate matrix, formed via polymerization-induced phase separation in a dual-curing epoxy–acrylate resin. Under mechanical loading, the rubbery matrix transfers load to the glassy domains, which dissipate energy through damage; upon unloading, the matrix elasticity restores the original shape of the material, while the thermally activated Diels–Alder chemistry heals the fractured epoxy domains. Digital light processing 3D printing enables precise control over both the dispersed-domain microstructure and complex macroscale architecture while preserving this damage-and-heal mechanism. Homogeneous samples reach a SEA of 1.77 kJ kg⁻ 1 at 50% compressive strain, and architected lattices tolerate strains as high as 0.6 yet recover nearly their initial stiffness and SEA after thermal healing. This damage-and-heal paradigm establishes a route to lightweight, reusable energy-absorbing architectures.