Windows go from transparent to opaque with the flick of a switch

Instead of drawing your blinds to get some privacy, what if you could just flick a switch and even adjust how much light you let in? Not impossible thanks to a technique developed by researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences.

The new technique can quickly change transform a window into a cloudy or clear surface — or somewhere in between — using geometry to adjust the transparency.

Previously developed tunable windows, as they are sometimes referred to,  have relied on electrochemical reactions to achieve this goal, which has proven to come with high manufacturing costs.

How it works

The window is made of a sheet of glass or plastic while lies between transparent, soft elastomers that are sprayed with a coating of silver nanowires. Once an electric voltage is applied, the the nanowires on  are begin to move toward each other from either side of the glass which squeezes and changes the appearance of the soft elastomer. The nanowires are not evenly laid on the surface of the glass, so the elastomer deforms unevenly, which causes light to scatter unevenly and turns the glass opaque in under one second.

 

According to Samuel Shian, postdoctoral fellow who worked on the technology, the process is similar to a frozen pond.

“If the frozen pond is smooth, you can see through the ice. But if the ice is heavily scratched, you can’t see through,” said Shian.

The researchers also discovered that the clarity of the window could be adjusted by adjusting the voltage. For example, if someone wanted a window only slightly clouded, less voltage should be applied than if a completely opaque window was desired.

The varieties of tunable glass that exist today use vacuum deposition to coat the glass, which makes for a rather expensive process. According to David Clarke, who also worked on the technology, this could be a less expensive way to create tunable windows because the process is not based on chemical reactions.

Instead, the nanowire layer can be sprayed or peeled onto the elastomer which makes it easily adjustable for different window sizes.

The team would like to now incorporate thinner elastomers, which would require lower voltages to work better with electrical supplies.

Harvard’s Office of Technology Development has filed a patent for the technology and working with glass manufacturers to bring the product to market.

Story via Harvard University.