Australian Engineers Develop Floating Titanium Lattice Stronger Than Steel

A team of Australian engineers has solved a problem that has long plagued designers of lightweight metal structures: how to make them float. The breakthrough came from RMIT University's Centre for Additive Manufacturing, where researchers developed a 3D-printed titanium lattice that not only stays afloat in seawater but also outlasts and outperforms the steel and plastic materials currently holding up jetties, buoys, and underwater sensors.

The core innovation is deceptively simple in concept, though it required new thinking to execute. Metallic lattices—frameworks of hollow, interconnected struts—can be made extraordinarily light, with densities less than one-tenth that of water. But this very openness is their fatal flaw: water flows into all that empty space, and the structure sinks. The RMIT team solved this by filling the hollow titanium struts with polyurethane foam. The foam traps air in tiny sealed cells, preventing water from flooding the channels even when the structure cracks or suffers other damage. The lattice itself remains open enough to let water pass through it, yet buoyant enough to stay afloat.

Dr Jordan Noronha, the lead researcher, explained the conceptual breakthrough that made this possible. Engineers had always calculated whether a structure would float using conventional density—a measurement that includes all the empty space within the lattice, even though water can occupy that space and contributes nothing to buoyancy. The team developed a new metric called skeletal density, which counts only the parts that actually exclude water: the titanium walls and the foam-filled channels. This gave them a simple design rule: if skeletal density is lower than the surrounding liquid, the structure floats. The principle sounds obvious once stated, but it required a fundamental shift in how engineers approached the problem.

The material's performance in testing was striking. Compared at equivalent overall density, the titanium lattice proved 70 percent stronger than the stainless steel or high-density polyethylene used in marine applications today. When researchers immersed samples in natural seawater from Melbourne's Port Phillip Bay for two weeks, the lattice lost only 0.15 percent of its mass, and its strength declined by less than 1 percent. Samples floated in freshwater for more than two months without sinking. Most crucially, the structure remained buoyant even after significant damage—cracking, broken connection points, and the fracture of an entire lattice layer. It sank only after being severely crushed and compacted, a threshold far beyond what conventional hollow marine structures could withstand.

The team demonstrated the technology with a 3D-printed marine buoy that held stable in a turbulent seawater tank tilted up to 45 degrees, without requiring a sealed casing, protective coating, or additional flotation devices. This proof of concept showed the material working under realistic stress conditions. Distinguished Professor Ma Qian, the project leader, said the next phase involves scaling up the demonstration parts and testing long-term performance in actual marine and deep-sea environments.

The potential applications extend well beyond floating infrastructure. Because the lattice is highly tailorable—researchers can change the material inside the titanium framework—the same structural approach could be adapted for energy absorption, thermal management, vibration control, and other uses. The research was led by RMIT in collaboration with the Conservatoire National des Arts et Métiers in France, with support from the Australian Research Council and RMIT's School of Engineering. What began as a solution to a specific marine engineering problem may open doors to an entirely new class of hybrid materials.