Could this metal inspired by spiders and ants create an ‘unsinkable ship’?

7 Nov 2019

The super hydrophobic structure remains afloat even after significant structural damage. Image: J Adam Fenster/University of Rochester

Researchers are very excited about a metal that refuses to sink, rising to the surface even after months of being submerged.

What are the possibilities of a metal that is so water resistant (hydrophobic) that it can stay submerged in water for months on end and still float to the surface instantly? That’s what researchers at the University of Rochester are trying to find out, following the creation of such a metal with the peculiar inspiration of diving bell spiders and rafts of fire ants.

In a paper published to ACS Applied Materials and Interfaces, the researchers said this new metallic structure uses a groundbreaking technique of femtosecond bursts of lasers to etch the surfaces of metals with intricate micro- and nanoscale patterns that trap air and make the surfaces super hydrophobic.

If such a metal were to be manufactured at a large scale, it could potentially be used to create an ‘unsinkable’ ship, a wearable floatation device that could still float after being punctured, or monitoring devices that could survive long-term ocean studies.

However, a notable issue with just using laser etching is that, over long periods of time, the surfaces of the metal may start to lose their hydrophobic properties. This is where the spiders and fire ants come in.

For example, Argyroneta aquatic spiders create an underwater dome-shaped web – called a diving bell – that they fill with air carried from the surface between their super-hydrophobic legs and abdomens. Similarly, fire ants can form a raft by trapping air among their superhydrophobic bodies.

Ready for commercial manufacturing

“The key insight is that multifaceted super-hydrophobic surfaces can trap a large air volume, which points towards the possibility of using super-hydrophobic surfaces to create buoyant devices,” the researchers wrote.

This led them to creating a structure with treated surfaces on two parallel aluminium plates that face inward as opposed to outward, making them enclosed and free from external wear and abrasion. These surfaces are separated enough to leave sufficient trapped air between each of the adjoining structures to create waterproof compartments.

Testing showed it maintained its super hydrophobic ‘superpower’ after two months of being submerged underwater. This was still possible after being punctured several times because air was trapped in the adjoining compartments.

The researchers, led by Chunlei Guo, said that while aluminium was used in these experiments, the etching process could be applied to any metal or even a different material. Also, by using more powerful lasers since their initial experiments, they are able to speed up the fabrication process to the point where it could be feasible for commercial manufacturing.

Colm Gorey was a senior journalist with Silicon Republic