The future of green technology

Researchers at MIT have developed a new surface coating for glass that is anti-fogging, self-cleaning and free of glare.
Written by Ina Muri, Weekend Editor

Researchers at the Massachusetts Institute of Technology have developed a new way of creating surface textures on glass that eliminate reflection and repel water droplets.

The new multifunctional glass is based on surface nanotextures that produce an array of conical features, is self-cleaning and resist fogging and glare, the researchers say.

Using an inexpensive manufacturing process, researchers hope the new glass can be used for optical applications, such as the displays of smartphones and televisions, solar panels, car windshields and even windows on buildings.

Hydrophobic coatings are not new to these surfaces, such as for solar panels. But MIT's new material is even more effective at repelling water and keeping the panels clean longer, the researchers say. In addition, existing hydrophobic coatings do not prevent reflective losses, another advantage for the new glass.

This new surface pattern -- consisting of an array of nanoscale cones that are five times as tall as their base -- is based on a new fabrication approach the researchers developed using coating and etching techniques adapted from the semiconductor industry. The glass surface is coated with several thin layers, including a photoresistant layer, which is then illuminated with a grid pattern and etched away. Successive etchings produce the conical shapes.

The team has already applied for a patent on the process.

Since it's the shape of the nanotextured surface that provides the material's unique characteristics, Park and Choi envision the manufacture of glass or transparent polymer films with the surface features by passing them through a pair of textured rollers while still partially molten. The process would not add significantly to the cost of manufacture, they say.

The researches drew their inspiration from nature, where textured surfaces ranging from lotus leaves to desert-beetle carapaces and moth eyes have developed in ways that satisfy multiple needs at once. Although the arrays of pointed nanocones on the surface appear fragile when viewed microscopically, the researchers say their calculations show they should be resistant to a wide range of forces, ranging from impact by raindrops in a strong downpour or wind-driven pollen and grit, to direct poking with a finger.Further testing will be needed to demonstrate how well the nanotextured surfaces hold up over time in practical applications.

“For the first time, as far as I am aware, this paper learns a lesson in manufacturing efficiency from nature by making an optimized antireflective and anti-fogging device” Andrew Parker said, a senior visiting researcher fellow at Oxford University’s Green Templeton College in the U.K. “ This may be the future of a greener engineering where two structures and two manufacturing processes, are replaced by one.”

For more information of the paper, go to ACS Nano: Nanotextured Silica Surfaces with robust Super-Hydrophobicity and Omnidirectional Broadband Super-Transmissivity.

This post was originally published on Smartplanet.com

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