Superhydrophobic material inspired by spiders and ants

Inspired by diving bell spiders and the rafts of fire ants, researchers at the University of Rochester in the US created a metallic structure that is so water repellent that it refuses to sink, even if it is littered with holes.

The material is made using a technique developed in 2015, which uses extremely short bursts of lasers to “etch” the surfaces of metals with micro- and nanoscale patterns. These patterns make the surfaces super hydrophobic. However, after being immersed in water for long periods of time, the surfaces may start losing their water repellent qualities.

This is where the diving bell spiders and the fire ants come in. These creatures can survive long periods under or on the surface of water by trapping air in an enclosed area. Diving bell spiders (Argyroneta aquatic) create an underwater dome-shaped web, which they fill with air carried from the surface between their superhydrophobic legs and abdomens. Fire ants do something similar by trapping air among their superhydrophobic bodies.

Inspired by the critters, the researchers created a structure in which the treated surfaces on two parallel aluminium plates face inward rather than outward, so they are enclosed and free from external wear and abrasion. The surfaces are separated by just the right distance to trap and hold enough air to keep the structure floating, creating a waterproof compartment. The superhydrophobic surfaces will keep water from entering the compartment even when the structure is forced to submerge in water.

Even after being forced to submerge for two months or being littered with holes, the materials immediately bounce back to the surface.

While the researcher used aluminium for this project, the etching process could potentially be used for any metals, and even other materials. By using more powerful lasers, the researchers make the process more commercially viable, which could lead to unsinkable ships or floatation devices.

Photos: University of Rochester / J. Adam Fenster