Architected material: Cross sections of the titanium lattice cube showing before and after being filled with polyurethane foam for buoyancy. (Courtesy: Sara Tan, RMIT)

Open-cell metallic structures are widely employed in the aerospace industry and in biomedical applications that require materials to be extremely light as well as strong. In marine infrastructure, however, their usefulness is limited because water quickly fills their interconnected open pores, preventing them from floating even though their bulk density is much lower than that of water.

Engineers in Australia and France have now developed a way around this problem.…