Dec 14, 2017 | By Tess

A research team from the University of Delaware is developing smart window panels which can easily switch between being reflective and transparent with the application of a special liquid. The windows, which are being developed with the help of 3D printing technologies, could be an affordable solution for improving heating and cooling efficiency for homes and cars.

So far, the researchers have already demonstrated that the modular window panels work and suggest that they will be easy to manufacture and have the potential to be more accessible than existing glass that uses voltage to change between clear and tinted (which reportedly costs up to $100 per square foot).

“We expect our smart glass to cost one tenth of what current smart glass costs because our version can be manufactured with the same methods used to make many plastic parts and does not require complicated electro-optic technology for switching," explained Keith Goossen, one of the project’s lead researchers.

How do these smart windows work? As the University of Delaware team explains, the windows consist of a plastic panel which is patterned with a retroreflective surface—meaning that it reflects light back in the direction the light is coming from—and a thin chamber layer on top of it, in which the special liquid, methyl salicylate, can be injected.

When the liquid is injected into the chamber, as can be seen in the demonstration video, the retroreflective panel surface gradually becomes transparent. Currently, the plastic panels are being manufactured using 3D printing technologies, and Goossen suggests that the research team is investigating new ways to process 3D printable plastics with good optical performance to advance the research.

Additive manufacturing enabled the researchers to test various retroreflective patterns by printing them as part of clear plastic panels and used special post-processing techniques to optimize the retroreflective surface of the 3D printed panel.

“Without 3D printing, we would have had to use a molding technology, which requires building a different mold for every different structure,” explained Goossen. “With 3D printing, we could easily make whatever structure we wanted and then run experiments to see how it performed.”

As it turns out, the 3D printed window panels performed well in optical tests, and showed no signs of degradation after many cycles of injecting and draining the liquid material. “For commercial production, we can use standard injection molding to inexpensively make the retroreflective panels,” added Goossen.

The innovative smart window could offer a number of benefits to the construction and automotive industries. For the latter, the panels could be built into cars and give driver’s the ability to keep their cars cool while parked by becoming retroreflective.

“You can't use today's commercially available switchable glass for this application because in the darkened state the windshield still absorbs sunlight and becomes hot,” elaborated Goossen. “Because our glass is retroreflective in the non-transparent state, almost all the light is reflected, keeping the glass, and thus the car, from getting hot.”

If you’ve ever burnt yourself while trying to buckle up, this possibility will undoubtedly be an exciting one.

Within the construction industry, the smart windows could have a number of applications. As the researchers explain, the window panels could be built into skyscrapers and not only offer the benefits of keeping sun out during summer and letting it in in the winter for efficient cooling and heating, but because the glass is retroreflective, light from the sun would be directed back upwards, which would help cut back on “city warming.”

The plastic 3D printed window panels could also be used in residential buildings, as they could provide a switchable surface that could alternately keep houses cool in summer and attract warmth in winter.

“Here in Delaware, you would like to have a white roof in the summer to keep the house cool and a dark roof in the winter to absorb sunlight and help lower heating costs,” said Goossen. “For smart roofing, our new technology offers a more effective type of cool roof because it is retroreflective while also allowing the roof to switch to dark in the winter.”

To increase the efficiency of the smart window panels in roofing scenarios, the researchers say that an additional layer of material could be placed under the plastic panels to absorb light and, consequently, warmth, providing better insulation to the house. Still, there are some kinks to be worked out, as the liquid used in the windows, methyl salicylate, freezes at around -9°C.

The researchers will continue to advance their 3D printed window research and ultimately hope to bring them to market as an affordable option for smart construction and automotive manufacturing.



Posted in 3D Printing Application



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