“Unsinkable metal” stays afloat even with holes punched in it


Superhydrophobic materials, which are excellent at repelling water, can be extremely useful for a whole range of reasons, both obvious and not-so-obvious. They can prevent ice from building up on surfaces, make electronics waterproof, make ships more efficient or keep people from peeing in public. Now engineers have found a quirky new use for superhydrophobic materials – making “unsinkable” metals that stay floating even when punctured. Superhydrophobic materials get their water-repelling properties by trapping air in complex surfaces. These air bubbles make it hard for water to stick, so droplets instead bounce or roll right off. But, of course, air also makes things buoyant, so the team set out to test how superhydrophobic materials could be used to make objects that float better. The researchers used ultra-fast laser pulses to etch microscale and nanoscale patterns onto the surfaces. That traps large volumes of air, making the metals both superhydrophobic and buoyant. But the problem was that these complex surfaces would eventually wear away due to friction in the water, reducing the effectiveness of both of those properties. So, the researchers came up with a creative solution. They built structures made up of two treated aluminium surfaces facing each other, connected by a small central pole. The distance between the two plates was carefully chosen to trap the maximum amount of air, like a waterproof compartment in the middle. The end result is virtually unsinkable, the team says. After being weighed down for two months, the structures jumped back to the surface as soon as the load was removed. Even damaging the surfaces didn’t make them sink – the team drilled six holes in them measuring 3 mm, and one measuring 6 mm, and the structures stayed afloat. Apparently, enough air remains trapped in other parts of the structure. The researchers say that the etching technique could be used on basically any metal or other material, and the resulting unsinkable devices could have a range of potential applications. Ships and flotation devices could stay afloat even after sustaining heavy damage, and electronic monitoring devices could keep running for long periods underwater. The work was conducted scientists at the University of Rochester and the Changchun Institute of Optics, Fine Mechanics, and Physics in China. The research was published in the journal ACS Applied Materials and Interfaces.

New Atlas, 6 November 2019
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