3D printing of hydrogel-infused gyroid lattices for tunable stiffness and cyclic durability

This study presents a process-enabled manufacturing route for producing hydrogel-infused additively manufactured gyroid lattices as tunable soft–hard composite structures for energy absorbing industrial and biomedical products. Stereolithography-printed gyroid lattices were fabricated using a flexible biocompatible resin and subsequently infused with selected hydrogel formulations to create interpenetrating solid–gel architectures. Four families of hydrogels —agarose, gelatin, poly(vinyl) alcohol, and poly(acryl)amide (PAAM)— were first screened under large strain compression to identify formulations suitable for infusion, gelation within confined lattice voids and resistance to repeated mechanical loading. Poly(acryl)amide hydrogels demonstrated the most favourable combination of toughness, recoverability and fatigue resistance and were therefore integrated into 3D-printed gyroid lattices with controlled porosity. Mechanical testing under static and cyclic loading revealed that hydrogel infusion results in new, emergent mechanical behaviour, with suppression of strut buckling, hybrid energy absorption, and a new failure mode. The new concept displayed increased structural stiffness (592%), and enhanced energy absorption (273%) compared to air-filled lattices. Importantly, the gel-gyroid composites retained mechanical integrity over 10,000 loading cycles, confirming their suitability for repeated-load environments. This work establishes a 3D printing manufacturing framework for producing customisable, energy absorbing lattices with potential applications in orthotic devices, protective structures, vibration damping components and other repeated-load environments.