Porosity-Dependent Metallization and Subsequent Strengthening of Additively Manufactured Porous Polymer Lattices

The use of polymerized high internal phase emulsions (polyHIPEs) combined with electroless nickel plating provides an effective route to fabricate architected porous polymers with enhanced structural performance. The resulting metallized lattices exhibit low density, high stiffness, and improved interfacial integrity, making them suitable for lightweight structural, catalytic, and energy-related applications. This study investigates the influence of porosity on metallization and mechanical reinforcement in 3D-printed polyHIPE lattices. A water-in-oil HIPE was used as a vat-photopolymerizable resin and printed via digital light processing (DLP) into lattice structures with target porosities of 80% and 87.5%, followed by electroless nickel coating. SEM revealed open-cell, interconnected morphologies with average pore sizes of 35.15 ± 17.47 µm (P80) and 41.55 ± 14.20 µm (P87.5). Surface and cross-sectional SEM/EDS confirmed uniform nickel deposition with penetration depths of 83 ± 21 µm (P80Ni) and 199 ± 86 µm (P87.5Ni), indicating more effective coating at higher porosity. Compression testing showed a compressive modulus increase from 0.27 ± 0.06 kPa for the polymer lattices to 159.70 ± 29.26 kPa and an ~85-fold increase in compressive strength after metallization. These results reveal a clear structure–property relationship between porosity, coating depth, and mechanical performance, demonstrating that electroless nickel plating effectively transforms lightweight polyHIPE lattices into robust, multifunctional architected materials.