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.