Continuous Stereolithography 3D Printing of Multi-Network Hydrogels in Triply Periodic Minimal Structures With Tunable Mechanical Strength for Energy Absorption

This work presents a fast additive manufacturing (AM) protocol for fabricating multi-network hydrogels. A gas-permeable PDMS (polydimethylsiloxane) film creates a polymerization-inhibition zone, enabling continuous stereolithography (SLA) 3D printing of hydrogels. The fabricated multi-bonding network integrates rigid covalent bonding and tough ionic bonding, allowing effective tuning of elastic modulus and strength for various loading conditions. The 3D-printed triply periodic minimal structures (TPMS) hydrogels exhibit high compressibility with up to 80% recoverable strain. Additionally, dried TPMS hydrogels display novel energy/impact absorption properties. By comparing uniform and gradient TPMS hydrogels, we analyze their energy/impact absorption capability of the 3D-printed specimens. We use finite element analysis (FEA) simulation studies to reveal the anisotropy and quasi-isotropy behavior of the TPMS structures, providing insights for designing and controlling TPMS structures for energy absorption. Our findings suggest that gradient TPMS hydrogels are preferable energy absorbers with potential applications in impact resistance and absorption.