Scientists at the University of Rochester, inspired by diving bell spiders and rafts of fire ants, have created a metal structure that is so water repellent that it refuses to sink ̵
Can this lead to an unreachable ship? Wearable flotation device that will still float after drilling? Electronic monitoring devices that can survive in the ocean in the long run?
All of the above, says Chunlei Guo, a professor of optics and physics whose lab describes the structure in ACS Applied Materials and Interfaces.
The structure utilizes an innovative technique developed by the laboratory to use femtosecond laser bursts to "trim" metal surfaces with complex micro- and nanoscale patterns that trap air and make surfaces superhydrophobic or water repellent.
However, researchers have found that after being submerged in water for long periods of time, surfaces can begin to lose their hydrophobic properties.
Enter spiders and fire ants that can survive long periods beneath or on the surface of the water. How? By capturing air in a confined area. Argyroneta water spiders, for example, create a dome-shaped underwater network – the so-called diving bell – that fills with air transferred from the surface between their superhydrophobic feet and abdomen. Likewise, fire ants can form a raft by trapping air in their superhydrophobic bodies.
"It was a very interesting inspiration," Goo says. As researchers noted in the article: "The key insight is that multilateral superhydrophobic (SH) surfaces can capture large volumes of air, indicating the possibility of using SH surfaces to create floating devices."
that the machined surfaces of two parallel aluminum plates face inwards and not outwards, so that they are closed and without external wear and tear. The surfaces are separated only at the right distance to hold and retain enough air to keep the structure floating – essentially creating a waterproof compartment.
Even after being forced to submerge for two months, structures immediately bounced to the surface after the load was released, Goo says. The structures also retained this ability even after being drilled repeatedly because the air remains trapped in other parts of the compartment or adjacent structures.
Although the team uses aluminum for this project, the "etching process" can be used for literally any metal or other material, "says Guo.
When the Guo lab first demonstrated etching technique, one needed an hour to draw a surface from one inch to one inch. Now, using lasers seven times as powerful and faster scanning, the lab speeds up the process, making it more scalable for commercial applications.
Dicobranches inspire a solid superhydrophobic material
Zhibing Zhan et al. Highly floating superhydrophobic metal mounting for water applications, ACS Application Materials and Interfaces (2019). Doi: 10.1021 / acsami.9b15540
University of Rochester
Spiders and ants inspire metal that won't sink (2019, November 6)
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