by Frank Fulton
Originally published in Glass Canada Magazine, June 2018 Issue
The next advancement in glass could be upon us in the form of nanotechnology.
Since the accidental invention of glass by Phoenician sailors 7,000 years ago, technological advances over the centuries have resulted in the development of broad sheet glass followed by crown glass, cast glass, drawn sheet glass and finally float glass. The next advancement in glass could soon be upon us in the form of nanotechnology.
The science now exists to practically eliminate surface reflections from glass, creating “invisible” glass. Watching television, working at a computer screen, taking photographs, or using a smart phone outdoors can all be negatively affected by glare created by the reflection of light. Not only will this technology improve the user experience for consumer electronic displays, it can also enhance the energy-conversion efficiency of solar cells by minimizing the amount of sunlight, and therefore energy, lost to reflection. When developed into a viable commercial process, reflection-free glass will certainly allow for some very creative architectural building designs while providing crystal-clear views at night from inside a lit room. When combined with low-E coatings, because light will not be reflected, the energy performance qualities of the coating will be maximized.
The scientists at the Center for Functional Nanomaterials (CFN) at the Brookhaven National Laboratory in Upton, N.Y., have developed the means to alter the surface properties of glass by adding a nanoscale-thick layer of cones or spikes that render it reflection-free and thereby nearly invisible.Nanotechnology and nanoscience are the study and application of extremely small things and can be used across all the other science fields such as chemistry, biology, physics, materials science and engineering. This science works in scales called nanometres. So, you ask, what is a nanometre? Well, it’s smaller than miniscule. One nanometre is one billionth of a metre. There are 25.4 million nanometres in a linear inch, and for comparative reference, a layer of 0.0007-inch anodized coating on aluminum is over 17 thousand nanometres thick. According to Chuck Black, the director of CFN and renowned as the expert scientist in his field, “your fingernails grow at a rate of one nanometre per second.”
Next you might ask why glass reflection happens in the first place. Consider that light travels through air at around 300,000 kilometres per second but when it gets to a piece of glass it can suddenly move at only 200,000 kilometres per second. This results in a photonic traffic jam of light at the glass surface creating a reflection. Each piece of clear glass reflects eight per cent of light. But the addition of a nanosized layer on the surface acts as a buffer between the air and glass, changing the speed of the light gradually instead of suddenly, allowing all of the light to transfer through the glass and thereby virtually eliminating a reflection.
How is the non-reflective nanolayer produced? Black states that “nanotextured glass is created by first coating the glass surface with a polystyrene (Styrofoam)/polymethylmethacrylate (Plexiglass) copolymer, heating it, then hardening it by infusing aluminum oxide. Once hardened, plasma etching is applied that removes the initial coating materials, leaving a uniform pattern of aluminum oxide particles behind. The etch eats away the glass surface around, but not beneath, the aluminum particles creating microscopic valleys and leaving behind miniature 170 nanometre tall peaks or spikes. A two-inch piece of glass has 900 billion spikes on its surface!”
Although there are applied coatings in the market that address glare on picture glass and specific colours seen through eye glasses, these treatments deal with only one wavelength of light whereas the nanotextured layer developed by Black and his team transmits the full spectrum of visible wavelengths. Their revolutionary process doesn’t add a coating that could be scratched or damaged but actually changes the physical properties of the glass. Additionally, not only does this treatment make the glass invisible and eliminate glare, it also makes it water-repellent, self-cleaning, and anti-fogging. Just imagine driving your car with this glass in your windshield!
Frank Fulton is president of Fultech Fenestration Consulting. He has been in the industry for 30 years and can be reached via email at firstname.lastname@example.org.
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