The glass panels that let light into our homes and offices have been seen as huge windows of opportunity for engineers in recent times. If the amount of light pouring through can be managed throughout the day, it could lessen reliance on energy-sapping air conditioner units, for instance. This has led to a number of examples of smart facades that keep interior spaces from overheating, and some that even harvest energy for lights and ventilation. But a new tunable window-tinting technology is claimed to do things the smart glass before it cannot, by allowing users control over brightness, color temperature and opacity.

Scientists from the University of Cincinnati (UC) teamed up with researchers from Hewlett Packard, Merck and National Taiwan University in developing the tunable windows. The team set out to produce an adaptation of the technology found in e-paper electronic displays that could scale to cover entire window panes without being prohibitively expensive.

Around three years in the making, the final, patent-pending design is claimed to be simple and cheap to manufacture. Two glass substrates enclose a layer of polymer, a set of electrodes, and micro-replicated polymer nubs. This results in a honeycomb-pattern coating that can be integrated into new windows or even rolled onto existing ones.

"Basically, one color has one charge," explains UC's Sayantika Mukherjee, who led the research. Another color has another charge, and we apply voltage to repel or attract the colors into different positions. The basic technology is not that different from what our group has previously demonstrated before in electronic display devices."

So, imagine if you could turn up the opacity for a bit of privacy, just as you would with regular blinds, without compromising on brightness? Or adjust the windows to bring feelings of warmth to your cold, bare basement, like you could with one of Phillips' Hue lightbulbs? The researchers say the tunable windows can make this possible. They report that when the windows are turned milky for privacy, they are capable of still letting through 90 percent of natural light.

Furthermore, the team says the system can allow for other types of configurations. This might involve controlling both visible light and infrared heat transmission at the same time. Such a function could find use in summer months to prevent the house heating up, or in the winter months to help keep it warm and toasty.

The researchers are hopeful that the solution will lead to inexpensive window tinting that replaces conventional shades and blinds.

The research was published in the journal Applied Optics.

The video below gives an overview of the technology.

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