3D-Printed Floating Titanium Lattice Stays Afloat

3D-printed floating titanium is the shop-materials story today: RMIT filled hollow lattice struts with polyurethane foam so a metal part can sit in water after it cracks. RMIT’s September 2026 release calls it the first reported floating metal-hybrid open-cell lattice and points to a paper in Advanced Materials. For a fabrication shop, the news is a buoyancy rule plus a foam fill — not a desktop metal printer you can order this week.

What's Happening

Open metal lattices can be lighter than water and still sink. Water walks into every cell. Dr. Jordan Noronha at RMIT’s Centre for Additive Manufacturing put the problem in one sentence: densities under one-tenth of water do not help if the voids flood. The team printed a titanium lattice of hollow, connected struts, then filled only those struts with polyurethane foam. Water can still move through the open cells. The sealed foam keeps gas in the walls. Samples floated in freshwater for more than two months. They stayed up after cracking, failed nodes, and the fracture of an entire lattice layer. They sank only after the cube was crushed and compacted.

The design rule is what they call skeletal density. Conventional density counts the empty space a lattice already has. Skeletal density counts only the titanium walls and the sealed, foam-filled channels — the parts that exclude water. If that number is below the density of the surrounding liquid, the structure should float even when every external opening is wet. Compared at the same overall density, RMIT reports the lattice is 70% stronger than the stainless steel or high-density polyethylene used in jetties, buoys, and floating sensors. Two weeks in natural seawater from Melbourne’s Port Phillip Bay cut mass by 0.15% and strength by less than 1%. A printed buoy stayed stable in a turbulent tank rotated to 45 degrees, with no sealed casing, coating, or extra float. Project leader Distinguished Professor Ma Qian said the next work is larger parts and longer marine and deep-sea tests. CNAM in France collaborated. “World-first” is the university’s phrasing.

Why 3D-Printed Floating Titanium Matters for Shops

A shop that prints fixtures already knows the cheap version of this problem: a hollow PLA float that works until one layer splits and the part drinks the tank. RMIT’s answer is metal walls plus a distributed foam barrier instead of one sealed skin. That is interesting if you build marine sensors, dock hardware, or anything that has to keep displacement after damage. It is not a coupon for a garage FFF printer. Laser powder-bed titanium and a foam fill are a foundry-class stack. The transferable idea is the split: what is allowed to flood, and what must stay sealed.

Keep the process map honest. This is not continuous fiber, and it is not a desktop composite job. A tow on a thermoplastic printer can stiffen a jig that sits on a bench. It will not print Ti-6Al-4V, and it will not qualify a buoy. Two-week bay immersion is a corrosion snapshot, not a multi-year marine certificate. The 70% strength figure is a same-density comparison in the release, not a field coupon bolted to a jetty.

How 3D-Printed Floating Titanium Compares to Shop Hardware

Part	Typical process	What fails first
HDPE / steel buoy	Molded plastic or welded shell	One crack floods the cavity
Open metal lattice	Powder-bed titanium, empty cells	Water fills the cells; it sinks
This foam-filled lattice	Hollow struts plus polyurethane	Stays up until crushed compact
Desktop FFF float	Hollow PLA or PETG	Layer split; not a marine metal
Continuous-fiber fixture	Thermoplastic plus a designed tow	Wrong tool if you needed buoyancy

What the Research Says

The new paper is Noronha and colleagues, “Breaking the Surface: Buoyant Metal–Polymer Open–Cell Hybrid Lattice Metamaterials,” in Advanced Materials (DOI 10.1002/adma.74641). The release restates the lab results: two-month freshwater float, buoyancy after cracked layers, 70% same-density strength versus steel or HDPE, 0.15% mass loss and under 1% strength loss after two weeks in bay water, and a tank buoy that held at 45 degrees. Those are the claims to take to the paper, not extra numbers invented here (Noronha et al., 2026).

The same group’s 2023 Additive Manufacturing paper is the process background. Noronha, Rogers, Leary, and colleagues printed FCC and FCCZ Ti-6Al-4V hollow-strut lattices at 8–16% relative density by laser powder bed fusion. Yield strength and elastic modulus sat at the upper empirical limits for solid-strut metal lattices at similar density. Fine (~20 µm) prior-β grains in the thin hollow walls helped, compared with coarser grains in solid-strut Ti-6Al-4V. That paper is about making and crushing hollow titanium struts, not about foam or seawater. It is why a foam fill was even an option: the walls already existed as a printable, load-bearing tube (Noronha et al., 2023).

Frequently Asked Questions

What is 3D-printed floating titanium?

It is a titanium lattice printed with hollow, connected struts, then filled with polyurethane foam so trapped gas keeps the part buoyant. RMIT reports the first demonstration of a floating metal-hybrid open-cell lattice. Water can move through the open cells, but the foam-filled struts stay sealed. Samples floated in freshwater for more than two months.

How strong is RMIT’s floating titanium lattice?

Compared at the same overall density, RMIT says the lattice is 70% stronger than stainless steel or high-density polyethylene used in marine hardware. After two weeks in Port Phillip Bay seawater it lost 0.15% of its mass and less than 1% of its strength. Those are lab and short tank figures, not a multi-year jetty coupon.

Can a desktop continuous fiber printer make floating titanium?

No. This work is metal powder-bed titanium with a foam fill, not fused filament. A desktop continuous-fiber machine can print a jig or bracket that keeps a load path on a shop floor. It does not print titanium, and it does not replace a marine buoy that has to stay afloat after a cracked cell.

Fibricate's Place in This Story

A foam-filled titanium lattice and a continuous tow answer different shop questions. Companies like Fibricate, whose FibreSeeker 3 continuous carbon fiber 3D printer lays thermoplastic with a tow from feedstock such as the continuous carbon fiber spool, are not printing Ti-6Al-4V or qualifying a bay buoy. Print fiber when the part is a clamp or fixture that should keep a load path on a bench or a cart. Reach for metal AM — and a buoyancy design — when the part has to sit in water after it cracks. Do not treat a desktop composite printer as a substitute for a powder-bed titanium lattice.

What to Watch Next

Watch whether Qian’s scale-up produces parts larger than a tank buoy, and whether a year in seawater still shows a 0.15%-class mass loss. Independent labs will want the skeletal-density rule on alloys that are not titanium, and on foams that are not polyurethane. Over the next 12–24 months, expect more hybrid lattices that flood on purpose and seal only the load path. The useful split for shops is who is buying metal AM for marine hardware, and who still needs a composite printer next to that cell for the fixtures that never leave the floor.

References & Further Reading

1. Noronha, J., et al. (2026). Breaking the Surface: Buoyant Metal–Polymer Open–Cell Hybrid Lattice Metamaterials. Advanced Materials.
2. Noronha, J., Rogers, J., Leary, M., Kyriakou, E., Inverarity, S. B., Das, R., et al. (2023). Ti-6Al-4V hollow-strut lattice materials by laser powder bed fusion. Additive Manufacturing.
3. Engineers create a world-first in floating titanium. RMIT University. Retrieved September 2, 2026.