Engineers Create A World-first In Floating Titanium That Could Transform Marine Technology

Imagine a metal structure that is stronger than many conventional marine materials, resistant to seawater, capable of surviving serious damage—and still able to float.

That is exactly what engineers have demonstrated in a world-first development led by researchers at RMIT University. The team has created a 3D-printed titanium lattice that combines a lightweight metal framework with polyurethane foam, producing a material that can remain buoyant even after significant structural damage.

The research, published in Advanced Materials, could open new possibilities for marine infrastructure, floating sensors, buoys and other technologies that need to be both lightweight and extremely durable.

The Problem With Floating Metal

Titanium is known for being strong, lightweight and highly resistant to corrosion. Engineers have also developed metallic lattice structures—frameworks made from interconnected hollow struts—that can achieve remarkably low overall densities.

But there was a major problem.

Even when the overall structure is lighter than water, the interconnected openings allow water to enter the lattice. Once the water fills these spaces, the structure can lose its effective buoyancy and sink.

Dr. Jordan Noronha, lead researcher at RMIT's Centre for Additive Manufacturing, described this as a fundamental challenge that had prevented lightweight metallic lattices from being practical for floating marine applications.

The new approach tackles that problem from a completely different direction.

A Titanium Skeleton Filled With Foam

Instead of sealing the entire lattice inside a protective shell, the researchers filled only the hollow titanium struts with polyurethane foam.

The result is a hybrid structure with two important components: a strong titanium framework that provides mechanical strength and foam-filled internal channels that help preserve buoyancy.

The external openings remain open, allowing water to move through the structure. Yet the water cannot simply flood the hollow titanium struts because the foam occupies their internal space.

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This creates an unusual combination: water can flow through the outside of the lattice while the structure retains enough buoyancy to remain afloat.

According to the researchers, the foam contains tiny sealed cells that trap gas. These cells act as a distributed barrier against water entering the hollow sections.

That becomes particularly important when the material is damaged.

A New Way to Think About Density

One of the most interesting aspects of the research is that the team developed a new concept called skeletal density.

Normally, when engineers calculate the density of an open lattice, they consider the entire volume occupied by the structure, including its empty spaces.

But those empty spaces can be filled by water.

So conventional density calculations don't necessarily tell engineers whether an open structure will actually float.

Skeletal density takes a different approach. It focuses on the portions of the structure that actually prevent water from occupying the space—such as the titanium walls and sealed, foam-filled channels.

The researchers say this provides a simple design principle: if the skeletal density is lower than the density of the surrounding liquid, the structure can remain buoyant even when water moves freely through its external openings.

This concept could potentially make the design of future floating structures much easier.

Stronger Than Conventional Marine Materials

The performance results are particularly impressive.

When compared at the same overall density, the titanium hybrid lattice was found to be 70% stronger than stainless steel or high-density polyethylene, two materials commonly used in marine applications.

That strength-to-weight advantage could be important for structures that need to remain lightweight while experiencing waves, impacts and mechanical loads.

The researchers also tested the material's resistance to seawater using natural seawater collected from Melbourne's Port Phillip Bay.

After two weeks of immersion, the lattice lost only 0.15% of its mass, while its strength decreased by less than 1%.

Although longer-term testing is still required, these early results suggest that the material can withstand short-term exposure to a harsh marine environment without significant degradation.

What Happens When the Material Breaks?

Perhaps the most surprising feature is what happens after damage.

Conventional hollow floating structures can have a serious weakness: once their walls crack, water can rapidly enter their internal spaces. This can dramatically reduce buoyancy and potentially cause the structure to sink.

The new titanium-foam lattice behaves differently.

Researchers deliberately subjected samples to serious damage, including cracking, failure at important connection points and the fracture of an entire lattice layer.

Despite this damage, the hybrid structure continued to float.

It eventually sank only after being severely crushed and compacted.

This means the material could potentially continue performing its basic floating function even after substantial structural failure.

The foam effectively provides numerous small sealed regions rather than relying on one large sealed cavity. Damage to one section therefore does not necessarily allow the entire structure to flood.

A Floating Buoy Survives Turbulent Seawater

The researchers didn't stop with laboratory samples.

They also created a 3D-printed marine buoy prototype to demonstrate how the technology could work in a realistic application.

The buoy remained stable inside a turbulent seawater tank that was rotated by as much as 45 degrees.

Importantly, it achieved this without requiring a sealed outer casing, protective coating or additional flotation system.

That could make the technology particularly attractive for marine equipment where reducing weight, complexity and maintenance is important.

Potential applications could include floating sensors, marine monitoring systems, buoys and components used in offshore infrastructure.

More Than Just a Floating Material

The researchers believe the technology could eventually go far beyond marine structures.

Distinguished Professor Ma Qian, who led the project, said the structure is highly tailorable. By changing the material placed inside the titanium framework, engineers could potentially give the same basic architecture completely different properties.

Possible applications include energy absorption, thermal management and vibration control.

This is where the research becomes particularly interesting.

Instead of thinking of the lattice simply as a lightweight floating material, engineers could potentially treat it as a customizable platform whose properties can be engineered for specific applications.

For example, one version could be optimized for buoyancy, another for absorbing impacts, and another for controlling heat or vibrations.

What Comes Next?

The current demonstration is an important proof of concept, but the researchers acknowledge that more work is needed before the technology can be deployed widely.

The next stage involves scaling up the structures and testing their long-term performance under realistic marine conditions, including challenging deep-sea environments.

Long-duration seawater exposure, pressure, repeated impacts, fatigue and manufacturing costs will all need to be investigated.

If the technology successfully passes these tests, however, it could provide engineers with a new class of lightweight marine materials.

A New Chapter for Floating Metals

The achievement represents more than simply making titanium float.

The researchers have shown that a metal-based lattice can combine low weight, high strength, corrosion resistance and damage-tolerant buoyancy by carefully controlling what happens inside its hollow structure.

The work, led by RMIT University's Centre for Additive Manufacturing in collaboration with the Conservatoire National des Arts et Métiers in France, demonstrates how additive manufacturing can be used to create material architectures that would be extremely difficult to produce using conventional manufacturing methods.

The bigger idea is simple but powerful: instead of changing the material itself, engineers can change its architecture to give it entirely new capabilities.

A titanium structure that once seemed destined to sink could now become the foundation for a new generation of floating technology.

Reference: J. Noronha, J. Tallon, R. Omar, et al. “ Breaking the Surface: Buoyant Metal–Polymer Open–Cell Hybrid Lattice Metamaterials.” Advanced Materials (2026): e74641. https://doi.org/10.1002/adma.74641