Light-intensity-programmed projection micro-stereolithography of dual-scale heterogeneous gradient metamaterials with layerwise matched material-structural modulus product

Lightweight protective materials are required to combine high stiffness, load-bearing capacity, and energy dissipation, yet these properties are often mutually constrained in architected metamaterials. Here, we present a material-architecture coupled design strategy for heterogeneous gradient Diamond (HG-Diamond) metamaterials fabricated by projection micro-stereolithography (PμSL). We programmed the solid material modulus over a broad range from 70 to 1572 MPa by regulating the curing light intensity, enabling spatial heterogeneity without changing the resin formulation. The specimens in our work utilized approximately 690–1230 MPa subset of this range. In parallel, we constructed a variable-stiffness Diamond architecture by introducing a z-dependent function into the conventional Diamond implicit equation, allowing the structural relative modulus to vary along the loading direction at a constant volume fraction. To couple these two gradients, we establish a matching criterion that equalizes the product of the material modulus and structural relative modulus across different layers, thereby assigning higher-modulus materials to deformation-prone regions. The resulting HG-Diamond transitions from inclined shear-band collapse to stable layer-by-layer crushing. Compared with the original Diamond, it achieves an 80% increase in compressive stiffness and a 58% increase in yield strength, with energy absorption density, specific energy absorption, and average plateau stress reaching 2.43 MJ/m 3 , 6820 mJ/g, and 3.79 MPa, respectively. Finite element analysis and deformation observations reveal that the simultaneous enhancement originates from gradient-induced stress redistribution and material-driven hardening of the initial collapse zone. Overall, the proposed strategy combines the single-vat, single-resin process with a volume-fraction-independent stiffness gradient, offering practical manufacturing and design advantages. By utilizing programmable material-architecture coupling, it simultaneously enhances stiffness, strength, and energy absorption capacity.