Australian Engineers Develop 3D-Printed Titanium That Floats On Water

A team of engineers at RMIT University has developed a 3D-printed titanium lattice material that floats in water, even after sustaining serious structural damage, pointing to potential new uses in marine infrastructure.

The material is made up of hollow, interconnected struts filled with polyurethane foam. Testing showed it not only maintains buoyancy but also withstands seawater exposure and outperforms the stainless steel and high-density plastic commonly used in jetties, buoys and floating sensors.

The research is the first reported demonstration of a floating metal-hybrid lattice metamaterial. Its sustained buoyancy was validated by samples that floated in freshwater for more than two months.

A long-standing barrier

Lead Researcher from RMIT’s Centre for Additive Manufacturing, Dr Jordan Noronha, explained that the team had overcome a fundamental challenge in making metallic lattice structures suitable for use in water.

“Although metallic lattices can be light – with densities less than one-tenth the density of water – their open, interconnected spaces allow water to enter, causing them to sink,” Noronha noted.

“This has made these strong, lightweight structures unsuitable for marine infrastructure – until now.”

The core of the solution involved filling only the hollow titanium struts with polyurethane foam, rather than sealing the entire structure.

“By filling only the hollow titanium struts with polyurethane foam, we created a structure that allows water to flow through it while remaining buoyant even after significant cracking and damage,” he added.

Rethinking how density is measured

To underpin the design, the researchers developed a new metric called skeletal density, which offers a way to predict whether open structures will float.

Conventional density calculations factor in all the open space within a lattice structure. However, because water can occupy that space, it does not contribute to buoyancy, making traditional measurements unreliable for these types of materials.

Skeletal density instead considers only the parts of the structure that exclude water: the titanium walls and sealed, foam-filled channels within the struts.

“This gives engineers a simple design rule: if the skeletal density is lower than that of the surrounding liquid, the structure will float – even when water flows through all its external openings,” Noronha outlined.

The concept gives designers a practical framework for engineering buoyant metallic structures without relying on sealed casings or external flotation devices.

Stronger than current alternatives

Testing revealed the titanium structure was 70 per cent stronger than the stainless steel or high-density polyethylene used in marine applications, when compared at the same overall density.

It also held up in short-term corrosion testing using natural seawater sourced from Melbourne’s Port Phillip Bay. After two weeks of immersion, the lattice lost only 0.15 per cent of its mass, while its strength declined by less than 1 per cent.

The hybrid lattice remained buoyant even after sustaining significant damage, including cracking, failure at key connection points and the fracture of an entire lattice layer.

It sank only after being severely crushed and compacted, underscoring its capacity to maintain flotation despite major structural compromise.

Foam acts as a distributed barrier

Noronha pointed out that the foam’s cellular structure plays a central role in maintaining buoyancy under duress.

“Tiny, sealed cells in the foam trap gas and prevent water from flooding the hollow struts,” he remarked.

“In this way the foam acts as a distributed barrier that helps the structure remain afloat after damage – unlike conventional hollow marine structures, which can rapidly fill with water after cracking.”

This characteristic could prove significant in marine environments where structures are routinely subjected to wave impacts, collisions and long-term fatigue, and where the failure of a sealed hull can lead to rapid flooding and loss of buoyancy.

Prototype buoy tested in turbulent conditions

The team demonstrated the technology by producing a 3D-printed marine buoy and placing it in a turbulent seawater tank. The buoy remained stable when rotated up to 45 degrees, without requiring a sealed casing, protective coating or additional flotation.

Project Leader and Distinguished Professor, Ma Qian, indicated that the next steps for the research include scaling up the demonstration components and testing long-term performance under realistic marine and deep-sea conditions.

He observed that the structure was also highly adaptable, and that the group was open to exploring a range of applications beyond marine infrastructure.

“By changing the material inside the titanium framework, we could tailor a similar structure for energy absorption, thermal management, vibration control and other applications,” Qian commented.

An international collaboration

RMIT’s Centre for Additive Manufacturing led the project in collaboration with the Conservatoire National des Arts et Metiers in France. The Australian Research Council and RMIT’s School of Engineering supported the research.

The study, titled ‘Breaking the surface: buoyant metal-polymer open-cell hybrid lattice metamaterials’, has been published in Advanced Materials (DOI: 10.1002/adma.74641). Organisations interested in partnering on the research can contact research.partnerships@rmit.edu.au.

Last Updated on September 3, 2026 by Nick Ross