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.
“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.”
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.
The research team — which includes López Jiménez; Pedro Reis, the Gilbert W. Winslow CD Associate Professor of Civil and Environmental Engineering and Mechanical Engineering; and Shanmugam Kumar of the Masdar Institute of Science and Technology in Abu Dhabi — has published its results this week in the journal Advanced Optical Materials.
Stacking the polymer deck
The current work arose from a related project by Reis, López Jiménez, and Kumar, in which they analyzed the light-transmitting properties of a simple block of PDMS — a widely used rubbery, transparent polymer. The polymer block contained some darkened regions, and the team was looking to see how deforming the block would change the light traveling through the material.
“It was a happy accident,” López Jiménez says. “We were just playing with the material, and we soon got interested in how we can predict this and get the numbers right.”
The researchers set out to fabricate a type of soft color composite — a material that changes color or transparency in response to external stimuli, such as electrical, chemical, or mechanical force. Reis and López Jiménez created a thin, rectangular stack of transparent PDMS sheets, mixed with a solution of black, micron-sized dye particles, that may be easily stretched, or deformed mechanically. With no deformation, the structure appears opaque. As it is stretched or inflated, the material lets in more light.
In initial experiments, the researchers shone a light through the polymer structure infused with dye particles and characterized the amount of light transmitted through the material, without any deformation. They then stretched the polymer perpendicular to the direction of light and measured both the thickness of the polymer and the light coming through.
A theory on light
They compared their measurements with predictions from their equation, which they devised using the Beer-Lambert Law, a classical optics theory that describes the way light travels through a material with given properties. The team combined this theory with their experimental analysis, and derived a simple equation to predict the amount of light transmitted through a mechanically deformed PDMS structure.
To verify their equation, Reis and López Jiménez carried out one more set of experiments, in which they clamped the PDMS structure in the shape of a disc, then inflated the material like a balloon, as they shone a light from below. They measured the amount of light coming through and found that as the material was stretched and thinned, more light came through, at exactly the same intensities that were predicted by their equation.
“We can predict and characterize the evolution of light as we strain it,” López Jiménez says. “If you give me the initial material properties and measure the incoming light intensity, we know exactly how much light will go through with deformation.”
He adds that going forward, he hopes to use the equation to help tune the transparency and optical transmittance of materials with more complex surfaces and textures.
“Soft color composites offer exciting opportunities to provide materials with switchable and tunable optical properties,” Reis says. “Applying this relatively simple but both robust and predictable mechanism is an exciting challenge worth pursuing for concrete engineering applications such as indoor light control through smart windows.”
Shengqiang Cai, assistant professor of mechanical and aerospace engineering at the University of California at San Diego, says that in addition to smart window technology, the group’s colored polymer may be used applied as a strain test for other materials.
“I imagine that a thin layer of such soft composite can be potentially used as nonlinear strain gauge,” says Cai, who was not involved in the study. “Through attaching a thin layer of the soft composite to an engineering structure, we may be able to visualize its surface deformation, which is clearly important information for monitoring the structure’s safety. The idea is very simple. However, functions of the system are very robust, as demonstrated by these authors.”
Read more: Scientists tune polymer material’s transparency
The Latest on: Soft color composites
[google_news title=”” keyword=”Soft color composites” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
via Google News
The Latest on: Soft color composites
- Best deals at Wayfair ahead of Memorial Dayon April 30, 2024 at 10:54 am
Here's a two-piece living room set that will transform your living room, while providing comfortable seating that includes multi-layer composite seat cushions that are crafted with pocketed springs ...
- Explicitly Feminist and Vibrantly Colorful, the Met’s ‘El Niño’ Shines in More Ways Than Oneon April 29, 2024 at 11:26 am
El Niño also has more explicitly feminist messaging; Mary here stands in for all mothers, particularly mothers who bring up children under oppressive patriarchal regimes. Her complicated feelings ...
- Palace Accused of Throwing 'Shade' at Meghan Markleon April 25, 2024 at 5:55 am
The Buckingham Palace Shop Instagram account has promoted its own brand of strawberry jam after Meghan soft-launched her preserve.
- The 31 best women’s pajamas and sets for sleeping in stylish comforton April 17, 2024 at 11:12 am
Not to mention, more than 4,000 happy purchasers say it’s “so soft to wear,” with one reviewer owning five of them in the many colors it’s offered in. If you’re all about prints and ...
- Nonlinear Mechanics of Shells and Plates in Composite, Soft and Biological Materialson January 25, 2024 at 12:39 am
Zhang, Jing Xu, Jie Yuan, Xuegang Ding, Hu Niu, Datian and Zhang, Wenzheng 2019. Nonlinear Vibration Analyses of Cylindrical Shells Composed of Hyperelastic Materials ...
- 14 Essential Photoshop Blend Modes (and What Each One Does)on December 19, 2023 at 7:48 pm
Screen takes the inverse of each color channel in both the selected layer and the composite of the other ... from your underlying combined layers. Soft Light works to either lighten or darken ...
- 10 Best Apple Watch Bands in 2024 to Match Your Style and Budgeton July 31, 2023 at 3:31 am
Several different colors are available ... as it features a clear, crystalline composite material made of soft and transparent TPU. The bands aren’t made of glass or crystal but look like ...
- The 2024 Ford Mustang: All the Colors Availableon May 14, 2023 at 5:01 pm
After having established a strong foundation in kinetic models in a previous webinar, part two delves into the exciting realm of machine learning and its transformative potential for composite ...
- How Much Does Composite Decking Cost?on April 20, 2023 at 6:59 am
Composite decks don’t have this issue because the material is not soft, fibrous ... the entire material is pre-dyed to the specified color, ensuring that the composite deck boards are highly ...
via Bing News