THURSDAY, MARCH 16, 2023
A nano-thin window coating technology developed by a University of Toronto engineering professor recently received $5 million in federal funding, moving it one step closer to commercialization.
Nazir Kherani co-founded 3E Nano Inc. in 2015, with a three-layered coating that can reportedly more than double the thermal protection for residential and commercial windows. The funding was awarded through Sustainable Development Technology Canada.
About the Coating
According to the U of T release, the 3E Nano coating comprises a nano-thin metallic film sandwiched between two sapphire-like nano-thin films. This three-layered dielectric-metal-dielectric stack is opaque to certain wavelengths of light, but not others.
Because of this, the coating can control the flow of light entering and leaving the building over three parts of the solar spectrum: the visible, the near-frequency infrared and the mid-frequency infrared. Near-infrared light, which accounts for almost half of the sun’s total energy, and mid-infrared light can reportedly be reflected way.
“Windows are the weakest energy link in any building,” said Kherani. “Think of heat escaping in the winter months and heat entering the cool, ventilated space during the summer months.
“A window’s resistance to heat flow is measured by R-value, which is the ability to prevent heat from flowing into or escaping from a building. Currently, 3E Nano windows—in prototype as well as in pre-alpha deployment—rate R8 and higher. This compares remarkably to an average window, whose R-value lies in a range from R1 of a single pane to R3, a dual pane.”
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A nano-thin window coating technology developed by a University of Toronto engineering professor recently received $5 million in federal funding, moving it one step closer to commercialization. |
The coating is described as a “one-dimensional structure which is nano-thin, yet strong,” applied by sputter deposition. This process throws argon atoms into an aluminum target in a vacuum system, knocking the aluminum atoms like billiard balls into a lightweight polymer substrate.
Researchers then add nitrogen gas, which creates a chemical reaction to form a colorless sapphire-like film only tens of nanometers thick, or approximately one-thousandth of the thickness of a hair strand. Combined with a nano-thin layer of silver, this creates a coating that can be tuned for optical and electrical properties.
“Combining earth-abundant aluminum and nitrogen results in a coating material similar to sapphire in its optical and structural properties,” Kherani said. “The stability and multi-functional character of the sapphire-like structure is suited to low-cost, high-volume manufacturing.”
Kherani and his team reportedly envision other aspects of the perfect window as integrated functionalities ranging from metamaterial structuring to dynamic systems that maintain ideal temperatures and daylighting within buildings.
“In the lab, we’ve created a metamaterial that retains low emissive and solar control properties but has high transparency in the gigahertz range critical for communication—nature-inspired with near-invisible hexagonal honeycomb patterns,” said Kherani.
The company previously received federal funding in 2017 for the low-cost energy-control coating that can be used for glass and other transparent media.
Recent U of T Window Research
In February, a new multilayered fluidic system developed by researchers at the University of Toronto was reported to have the potential to reduce energy costs in buildings, inspired by the skin of certain species of squid.
U of T reported that current “smart” building technologies, like automatic blinds or electrochromic windows, can be used to control the amount of sunlight that enters a room. However, researchers said that these systems are limited in that they cannot differentiate between different wavelengths of light or can control how that light gets distributed spatially.
As an alternative, the team developed a platform that optimizes the wavelength, intensity and dispersion of light transmitted through windows using microfluidics. The prototypes reportedly consist of flat sheets of plastic that are permeated with an array of millimeter-thick channels to pump fluids through.
Then, customized pigments, particles or other molecules can be mixed into the fluids to control what kind of light gets through and in what direction the light is distributed. The sheets can also be combined into a multi-layered stack with different optical functions, such as controlling intensity, filtering wavelength or tuning the scattering of transmitted light indoors.
This method can be digitally controlled by pumps to add or remove fluids from each layer, optimizing light transmission within the system.
According to the release, the study was inspired by multilayered skin of a squid, which contains stacked layers of specialized organs. This includes chromatophores and iridophores, which control light absorption and impact reflection and iridescence, respectively.
U of T researchers reportedly built detailed computer models that analyzed the potential energy impact of covering a hypothetical building in this type of dynamic façade, informed by physical properties measured from their prototypes. The team also then simulated various control algorithms for activating or deactivating the layers in response to changing ambient conditions.
Tagged categories: Coating Materials; Coating Materials - Commercial; Coatings; Coatings Technology; Coatings technology; Coatings Technology; Colleges and Universities; Energy efficiency; Funding; Nanotechnology; Program/Project Management; Research and development; Solar energy; Windows
