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An ‘unsinkable ship’? Super-hydrophobic metal stays afloat even after major damage

Professional Engineering

The super-hydrophobic structure remains afloat even after significant structural damage from six 3mm holes and one 6mm hole (Credit: J. Adam Fenster/ University of Rochester)
The super-hydrophobic structure remains afloat even after significant structural damage from six 3mm holes and one 6mm hole (Credit: J. Adam Fenster/ University of Rochester)

A super-hydrophobic metallic structure that floats even after being punctured could inspire ‘unsinkable ships’, its creators have claimed.

Inspired by rafts of fire ants and diving bell spiders, the structure created by researchers at the University of Rochester in New York state reportedly refuses to sink no matter how often it is forced underwater. As well as boats, the team said it could be used for puncture-resistant flotation devices or ocean-monitoring devices.

Professor Chunlei Guo’s laboratory developed a technique using femtosecond laser bursts to etch metal surfaces with intricate micro- and nanoscale patterns, which trap air and make the surfaces super-hydrophobic, or water repellent. The researchers found, however, that the surfaces lost their hydrophobic properties after being immersed in water for long periods.

To tackle the issue, the team took inspiration from nature. Fire ants form rafts by trapping air among their super-hydrophobic bodies, while argyroneta aquatic spiders create underwater dome-shaped webs, like diving bells, that they fill with air carried from the surface between their super-hydrophobic legs and abdomens.

The researchers created a structure with treated surfaces on two parallel aluminium plates facing inward, enclosed and free from external wear and abrasion. The surfaces were separated by just the right distance to trap and hold enough air to keep the structure floating, in essence creating a waterproof compartment.

Even after being submerged for two months, the structures immediately bounced back to the surface after the load was released. They also retained this ability even after being punctured multiple times, because air was trapped in remaining parts of the compartment or adjoining structures.

The team used aluminium for the project, but Guo said the process could use other metals or materials.

The work was described in ACS Applied Materials and Interfaces.

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