Superhydrophobic covering makes the metal unsinkable
Superhydrophobic materials that completely repel water are very useful materials for a number of obvious and not-so-obvious reasons. Such materials can protect surfaces from icing or corrosion, make electronics waterproof, and recently engineers have found another use for superhydrophobic materials, the coating of which can make various metal products unsinkable, regardless of their shape and even the presence of through holes.
Superhydrophobic materials get their amazing properties by being able to trap and hold air near their surface. These air bubbles form a barrier that prevents water from making contact and wetting the surface of the material. However, the same air can just as well impart positive buoyancy to the material, which was used in this work.
Using ultrafast pulses of a powerful laser, the researchers created a specially ordered matrix of nanoscale objects on the metal surface. These objects trap and hold sufficiently large air bubbles to form a superhydrophobic covering. However, the problem lies in the fact that due to friction in water, nanosized objects are quickly erased and the efficiency of water repulsion by the surface is sharply reduced.
The solution to this problem was a structure of two metal surfaces connected to each other at some distance. At the same time, the distance between the plates was carefully calculated in order to capture and hold the maximum possible volume of air between them.
As a result, scientists have received a metal product that does not sink in water. This product was forcibly submerged under water and spent more than two months in this state. And after the scientists removed the holding weight, the metal disc floated to the surface immediately. The positive buoyancy of this disk was preserved even after the scientists drilled several through holes in it, with a diameter of 3 to 6 millimeters, the air retained in other parts of the structure was enough to provide positive buoyancy.
Despite the apparent simplicity and the lack of any innovation in all this, this technology will make it possible to make unsinkable things from metals and other materials. Vessels and submersibles made using such technologies can stay afloat even after sustaining severe damage, and specialized electronic devices can operate continuously underwater for much longer than any other existing technology.
In conclusion, it should be noted that this work was carried out jointly by scientists from the University of Rochester and the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences.
