Researchers at the University of Rochester are inspired by nature by “mining” features of spiders and ants to create a metal structure so water-repellent that it literally refuses to sink.
The unsinkable material has characteristics such as to remain afloat regardless of its time in water, whether it is damaged or perforated.
Could this lead to an unsinkable ship?
An invincible vessel is the first thought that comes to mind, but it is clear that there are many possible applications. A wearable life preserver that will still float, even after being punctured? Electronic monitoring devices that can survive long-term in the ocean?
The discovery is the result of the work of a team from the University of Rochester and Chunlei Guo, professor at the Changchun Institute of Optics, Fine Mechanics and Physics in China. The lab he described the research in the scientific journal ACS Applied Materials and Interfaces.
The project was supported by funding from the Bill & Melinda Gates Foundation, the US Army Research Office and the National Science Foundation.
Daughter of a laser
The facility uses a revolutionary technique developed by the lab to “etch” metal surfaces with a femtosecond laser. By etching intricate micro- and nanoscale patterns, it is possible to trap air and make surfaces superhydrophobic or water-repellent.
Natural inspiration
The characteristic conferred to the "unsinkable metal" is already present in nature: some species of spiders and ants can survive for long periods under or on the surface of water by trapping air in an enclosed area. Argyroneta water spiders, for example, create a dome-shaped underwater web, a so-called diving bell, which they fill with air carried from the surface between their super-hydrophobic legs and abdominals. Similarly, fire ants can form a raft by trapping air between their superhydrophobic bodies.
The problem and the solution
“This was a very interesting inspiration”, he claims Guo. As the researchers note in the document: “The key insight is that faceted superhydrophobic (SH) surfaces can trap a large volume of air, which points to the possibility of using SH surfaces to create floating devices.”
Guo's laboratory created a structure in which the treated surfaces on two parallel aluminum plates face inward, not outward, therefore closed and free from external wear and abrasion. The surfaces are separated by the right distance to trap and retain enough air to keep the structure floating, in essence creating a waterproof compartment.
Even after being submerged for two months, the structures immediately bounced to the surface after the load was released. The structures also retained this capacity even after being punctured multiple times, because air remains trapped in the remaining parts of the compartment or in adjacent structures.
Although the team used aluminum for this project, the “etching process” could make any material or metal unsinkable,” says Guo.
The first engraving experiments took some time: for an area of 2,5 square centimeters it took an hour.
