A new way of creating surface textures on glass that eliminates reflection and causes water droplets to bounce right off has been developed by researchers at MIT.
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.
Ultimately, they hope it can be made using an inexpensive manufacturing process that could be applied to optical devices, such as screens of smartphones and television, solar panels, car windshields and even windows on buildings.
While some earlier work has treated solar panels with hydrophobic coatings, the new multifunctional surfaces by the MIT team are 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, giving the new system yet another advantage.
This new surface pattern—consisting of an array of nanoscale cones that are five times as tall as their base of with on 200 nanometers—is based on a new fabrication approach the MIT team developed using coating and etching techniques adapted from the semiconductor industry. The glass surface is coated with several thin layers, including a photoresist layer, which is then illuminated with a grid pattern and etched away; successive etching produce the conical shapes. The team has already applied for a patent on the process.
Since the shape of the nanotextured surface—rather than any particular method of achieving that shape—that provide the unique characteristics, Park and Choi say that in the future, glass or transparent polymer films might be manufactured with such surface features simply by passing them through a pair of textured rollers while still partially molten; such a process would add minimally to the cost of manufacture.
The researches say they drew their inspiration from nature, where textured surfaces ranging from lotus leaves to desert-beetle carapaces and moth eyes have developed in ways that often fulfill multiple purposes 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.