Researchers from the University of Rochester have created a metallic structure so water repellent it’s virtually unsinkable, no matter how often its submerged, damaged or punctured.
The research team, led by Chunlei Guo, was inspired by diving bell spiders and rafts of fire ants that use their water-repelling legs and bodies to trap air in order to float on the water’s surface. Guo and his team believe the new metallic structure could be used in a variety of different ways, like in the construction of unsinkable ships or wearable flotation devices that will maintain their buoyancy despite being punctured or damaged.
In order to create this unsinkable metallic structure, the team used concentrated bursts of laser beams to etch the surface of the metals with intricate patterns that trap air, making them super-hydrophobic, or water-repellent. Unfortunately, researchers discovered that after being submerged in water for a long period of time the surface etchings began to lose their hydrophobic properties. That’s where the bell spiders and fire ants came into the equation.
Diving bell spiders are able to create a dome-shaped web that they fill with air and then carry it between their water resistant legs and abdomen. Similar, fire ants are able to survive long periods of time on the surface of the water by joining their limbs together to form a raft-like shape.
By using the insects’ method of preserving air in bubbles, Guo was able to ensure that even after extended periods of time submerged in water, the metal structure would manage to hold enough air to be able to float when returned to the surface.
To achieve this, Guo’s lab team created a structure in which the treated surfaces on two parallel aluminum plates face inward, not outward, so they are enclosed and free from external wear and abrasion. The two surfaces are then separated just enough to trap and hold enough air to keep the structure floating, creating a waterproof compartment.
Amazingly, after being completely submerged and held down for two months, the structure returned right back to the surface of the water. Although the team used aluminum for this project, the etching process can be performed on any metal, expanding the possibilities for this technology.
Super-hydrophobic structure remains afloat even after significant structural damage—punctured with six 3-millimeter diameter holes and one 6-millimeter. Credit: Hole/rochester.edu
The research project was funded by the Bill and Melinda Gates Foundations, the US Army Research Office, and the National Science Foundation.