Fly eyes inspire new anti-fog coating

Scientists have developed a new anti-fog coating modelled on the nano-structure of a fly eye that could one day be used on windows for cars, planes and buildings.
Professor Shi Xue Dou and team at the University of Wollongong's Institute for Superconducting and Electronic Materials in Australia, along with colleagues from China have been inspired by the eye of the common green bottle fly (Lucilia sercata) to make a new anti-fogging material.
The fly eyes can see clearly in moist environments without fogging up.
Fogging occurs when moisture drops of larger than 190 nanometres in diameter form on surfaces, scattering light and making the surface more difficult to see through.

The researchers found that when the green bottle fly was put in a humid environment with droplets of less than 10 micrometres, condensation only occurred on its body, but not on its compound eyes.
Looking more closely with microscopes, they found the 5 millimetre eyes were made up of thousands of repeating hexagonal units, each with a diameter of the order of 20 micrometres, 'ABC Science' reported.

These units were covered with numerous, near hexagonal bubble-like protuberances with diameters of around 100 nanometres.
"We suspect that these well-ordered, close packed, hierarchical hexagonal nanostructures are one of the origins of the superior superhydrophobicity and anti-fogging properties of the green bottle fly eyes," researchers said in a study published in the journal Small.

The researchers used zinc nanoparticles to assemble small hexagonal structures to mimic the fly's eye.
"By investigating the surface structure of the compound eyes of the green bottle fly, we successfully synthesised hierarchically-mimicking bio-inspired inorganic nanostructures via a two-step molecular self-assembly method," researchers said.
After constructing the material, the researchers then tested it and found that it was superhydrophobic just like the insect's eye.
Being superhydrophobic means water cannot wet the material and this paves the way for it being used for anti-fogging, and also anti-freezing, anti-corrosive and self-cleaning, researchers said.