Everyone knows that metals are a rather heavy class of substances that have a high density and (if we are not talking about special alloys or ultra-thin sheets like foil) often sinks in water. However, researchers from the University of Rochester were able to create metal that simply refuses to sink. Even if it is specially submerged under a water surface – it will float to the surface.
Responsible for the development is Professor of the Department of Optics and Physics, University of Rochester, Chunlei Guo and his team. To create a new material, researchers used an innovative method that uses femtosecond laser flashes to “etch” the surface of metals. That is, very fast and intense laser flashes create micro- and nanoscale patterns on the metal surface, changing the structure of the substance. Due to this, the surface layer of the metal can trap air and hold it, which makes the surface of the metal “superhydrophobic” or, quite simply, water repellent.
“Such an approach can lead to the creation of unsinkable ships. Or to the development of electronic devices that will not only float on the surface, they will also be almost completely waterproof.” – says Professor Chunlei Guo.
However, during the tests, the researchers found that after prolonged immersion in water, surfaces can begin to lose their hydrophobic properties. And then the attention of scientists attracted … spiders and ants.
For example, Argyroneta water spiders create an underwater domed web – the so-called diving bell, which they fill with air, which they carry from the surface on their legs and abdomen. In exactly the same way, some species of ants are able to form a “water bubble” by holding air bubbles on the surface of the body.
“This is a very interesting natural phenomenon,” the researchers note. The key in this case is that superhydrophobic (SH) surfaces can trap a large volume of air, which indicates the possibility of using SH-surfaces to create floating devices.
As a result, a team of scientists developed a structure in which two metal plates were covered with tiny “patterns” just like before. Only now they put these plates on top of each other, drawing the “pattern” inward. There was enough space between the plates to capture and hold air, which did not allow the metal structure to sink. Moreover, the superhydrophobic structure remains afloat even after significant structural damage. As part of the experiment, scientists made 6 holes in the plates with a diameter of 3 millimeters and one hole with a diameter of 6 millimeters. The plates continued to float on the surface of the water.
A team of scientists claims a similar process can be applied to modify any kind of metal. When experts first tested the new technology, it took them one hour to modify the area of the metal measuring 2.5 by 2.5 centimeters. Now, using lasers seven times more powerful, the process has accelerated significantly and in general, according to the developers, “the technology is ready for commercial use.”