Glass has two key properties, one good, one bad. The good one is that it's transparent, so we don't have to drive around in cars using periscopes to see. The bad one is that it's reflective, which can cause glare and other problems. If you've ever driven around with a white envelope or piece of paper on top of your dashboard, you know how annoying the reflection is.
The reflectivity issue is a problem with solar panels, where a percentage of that precious sunlight they're trying to soak up is uselessly bounced away. In an effort to solve this, a team of MIT researchers have found a way to etch the surface of glass in such a way that it "virtually eliminates reflections, producing glass that is almost unrecognizable because of its absence of glare." A nice side benefit of this is that water and dust will also not stick to the glass.
What the researchers have done is etched a "nanotexture"—essentially a forest of cones—into the surface of the glass, and the scale of this forest is so tiny that water droplets and dust particles cannot get any purchase. They bounce right off of the surface, as you can see in the video below. It also solves the original goal of preventing glare, as the sharp angle of the cones simply obviates the angles of incidence that a ray of light would bounce off of on a perfectly flat surface.
The applications of this technology would be immense: Imagine eyeglasses, windows, computer monitors and windshields you never have to clean, to say nothing of the increased solar panel efficiencies the team was initially after. In order to achieve widespread uptake the manufacturing techniques will need to be made affordable, which is what the research team is looking into now. And interestingly enough, the inspiration for the nanotexture is biomimetic.
Since it is the shape of the nanotextured surface—rather than any particular method of achieving that shape—that provides 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 researchers 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.
An MIT News article explains the generalities of the technology here. Materials geeks seeking more in-depth explanation can check out the research paper here.
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