Three colors of PDMS — a widely used rubbery, transparent polymer — are inflated like a balloon
as light from a light box shines from below. The top row shows the PDMS material before being inflated.
The bottom row shows the PDMS inflated, revealing the MIT logo placed underneath.
Photo: Melanie Gonick/MIT
(January 23, 2016) Material may offer cheaper alternative to smart windows.
If you’ve ever blown up a balloon or pulled at a pair of pantyhose, you may have noticed that the more the material stretches, the more transparent it becomes. It’s a simple enough observation: the thinner a material, the more light shines through.
Now MIT scientists have come up with a theory to predict exactly how much light is transmitted through a material, given its thickness and degree of stretch. Using this theory, they accurately predicted the changing transparency of a rubber-like polymer structure as it was stretched like a spring and inflated like a balloon.
Francisco López Jiménez, a postdoc in MIT’s Department of Civil and Environmental Engineering, says the researchers’ experimental polymer structure and their predictive understanding of it may be useful in the design of cheaper materials for smart windows — surfaces that automatically adjust the amount of incoming light.
MIT postdoc Francisco López Jiménez stretches a rectangular sheet of the polymer
PDMS he and his colleagues used to predict how much light is transmitted when a
specific mechanical force is applied. Photo: Melanie Gonick/MIT
“For buildings and windows that automatically react to light, you don’t have to spend as much on heating and air conditioning,” López Jiménez says. “The problem is, these materials are too expensive to produce for every window in a building. Our idea was to look for a simpler and cheaper way to let through more or less light, by stretching a very simple material: a transparent polymer that is readily available.”
Using a new theory that predicts how much light is transmitted through a material,
MIT scientists have developed a polymer structure that may be useful in designing
cheaper materials for smart windows — surfaces that automatically adjust the
amount of incoming light. Video: Melanie Gonick/MIT
López Jiménez envisions covering window surfaces with several layers of the polymer structure. He says designers could use the group’s equation to determine the amount of force to apply to a polymer layer to effectively tune the amount of incoming light.