New glass created to be self-cleaning and anti-fogging
US researchers have created a new glassy material that is anti-fogging, self-cleaning and almost entirely eliminates reflections.
The team at the Massachusetts Institute of Technology (MIT) believe it can be made using an inexpensive manufacturing process that could be applied to optical devices, the screens of smartphones and televisions, solar panels, car windshields and even windows in buildings.
The surface pattern — consisting of an array of nanoscale cones that are five times as tall as their base width of 200 nanometers — is based on a new fabrication approach the MIT team developed using coating and etching techniques adapted from the semiconductor industry.
Fabrication begins by coating a glass surface with several thin layers, including a photoresist 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 is the shape of the nanotextured surface — rather than any particular method of achieving that shape — that provides the unique characteristics, the team 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.
In touch-screen devices, the glass would not only eliminate reflections, but would also resist contamination by sweat.
Applications include photovoltaic panels which can lose as much as 40 percent of their efficiency within six months as dust and dirt accumulate on their surfaces and more than 50% through reflection depending on the time of day.
Meanwhile the device could be useful optical devices such as microscopes and cameras to be used in humid environments, where both the antireflective and anti-fogging capabilities could be useful. In touch-screen devices, the glass would not only eliminate reflections, but would also resist contamination by sweat.
The research was funded by the Army Research Office through MIT’s Institute for Soldier Nanotechnology.