Optical elements fogged up no more

Developing a vision-based system for the transportation sector is a far cry from building a system that performs inspection tasks in a factory setting. In transportation systems, many environmental issues such as extremes in temperature and humidity must be taken into account. What's more, engineers must also contend with dealing with the dirt and dust found in the natural environment that could affect the performance of their systems.

Now, thanks to researchers at the Massachusetts Institute of Technology (MIT, Cambridge, MA, USA), those environmental issues commonly addressed by systems' developers in the world of transportation may finally become a thing of the past.

That's right. You see, what the MIT researchers have done is to develop a new type of glass with a nano-textured array of conical features on its surface that not only resists fogging and glare but is self-cleaning too.

The surface pattern on the glass itself consists of an array of nanoscale cones that are five times as tall as their base width of 200 nanometers. It is created 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.

Ultimately, the researchers hope that the surface pattern can be made using an inexpensive manufacturing process that could be applied to a plethora of optical devices, the screens of smart phones and televisions, solar panels, car windshields and even windows in buildings.

According to mechanical engineering graduate student Kyoo-Chul Park, a photovoltaic panel can lose as much as 40 percent of its efficiency within six months as dust and dirt accumulate on its surface. But a solar panel protected by the new self-cleaning glass would be more efficient because more light would be transmitted through its surface. What's more, while conventional glass might reflect more than 50 percent of the light, the anti-reflection surface would reduce this reflection to a negligible level.

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 nano-cones on the surface appear fragile, the researchers say 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 nano-textured surfaces hold up over time in practical applications.

In a nod to the vision industry, the researchers say that -- aside from solar panels -- the new glass could be used in optical devices such as microscopes and cameras that are be used in humid environments, where both the anti-reflective 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 news will surely peak the interest of those engineers currently using more elaborate ways to contend with such issues in the transportation sector. For them, the commercialization of products based on such technology will not come soon enough.