Breaking Stiffness-Tunability Trade-offs in Metamaterials: a Minimal Surface Guided Hybrid Lattice Strategy.

A longstanding trade-off between stiffness and tunability has significantly constrained the multifunctional potential of architected metamaterials. Here, a generalizable design framework is introduced that integrates shell- and plate-based lattice architectures via a spatially compensated Boolean fusion strategy. The design enables tunable architectures with optimized mechanical robustness. The capability is demonstrated through two representative configurations: one based on Primitive TPMS and one on IWP TPMS, each fused with simple cubic plate lattices. The resulting structures are fabricated with high geometric fidelity using PolyJet printing and evaluated across multiple scales using homogenization, quasi-static compression testing, and finite element analysis. Compared with similarly ultrastiff plate lattices, the hybrid structure achieves a 213.98% increase in the tunable range of effective elastic modulus. The hybrid lattices reach 137.34% and 110.84% of the Hashin-Shtrikman upper bound for Young's modulus at relative densities of 0.33 and 0.34, respectively. Compared to single lattices, the hybrid designs show significant improvements: ultimate stress increased by up to 690% and specific energy absorption increased by 110%. The proposed metamaterials offer excellent tunability and mechanical performance, providing the flexibility to tailor structural behaviors for diverse applications such as biomedical engineering, acoustic isolation, and intelligent infrastructure systems.