Researchers say the polymer-based material allows sunlight to enter, maintains a more comfortable indoor climate without additional energy and cleans itself like a lotus leaf. Photo: Gan Huang / KIT.

Researchers have created a new film that, when placed on glass, reduces heat buildup, adds privacy and cleans itself. The film is known as polymer-based micro-photonic multi-functional metamaterial (PMMM) and was developed by researchers at the Institute for Microstructure Technology and the Light Technology Institute at Karlsruhe Institute of Technology.

The researchers say the polymer-based material allows sunlight to enter, maintains a more comfortable indoor climate without additional energy and cleans itself like a lotus leaf (a lotus leaf’s micro-topography ensures that water beads collect dirt as they roll off, cleaning the leaf without using detergent or expending energy). The researchers say the new material could replace glass components in walls and roofs.

The material features microscopic silicone pyramids. These micro-pyramids measure about 10 micrometers, about one-tenth the diameter of a hair. The design gives the PMMM film several functions: light diffusion, self-cleaning and radiative cooling while maintaining high transparency.

“A key feature is an ability to efficiently radiate heat through the Earth’s atmosphere’s long-wave infrared transmission window, releasing heat into the cold expanse of the universe,” says co-author Bryce Richards. “This allows for passive radiative cooling without electricity consumption.”

Tests in the lab and outdoors revealed that the film reduced cooling by 10 degrees Fahrenheit compared to the ambient temperature. The microscopic pyramids also scattered 73% of the light, giving off a frosted look. Even with the blurry appearance, the film’s transparency was 95%, compared to glass’ typical transparency of 91%.

“When the material is used in roofs and walls, it allows for bright yet glare-free and privacy-protected indoor spaces for work and living,” says lead author Gan Huang. “High light transmittance could increase yields in greenhouses because the photosynthesis efficiency is estimated to be 9% higher than in greenhouses with glass roofs.”

The film is also self-cleaning. The microscopic pyramids force water to bead in droplets, removing dirt and dust from the surface.

Richards says the new materials can be used in various applications, contributing to sustainable and energy-efficiency architecture. Huang adds that the film is scalable and can be “seamlessly integrated into plans for environmentally friendly building construction and urban development.”

1 Comment

  1. On the PMMM film, can you please advise and inform:
    1. Mode/system of application
    2. Measured resistance to scratches
    3. Self-cleaning? What type of “dirt”? Salt mist? Carbon base? ?????

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