Scientists create self-cleaning, energy-saving building material inspired by lotus leaves

Cooling, light-transmissive, and glare-free: the new material combines several unique properties. Credit: Gan Huang, KIT.

Researchers at the Karlsruhe Institute of Technology (KIT) have developed an innovative material that could revolutionize building construction.

This new polymer-based material, described in the journal Nature Communications, lets sunlight in, keeps indoor spaces comfortable without extra energy, and cleans itself like a lotus leaf.

It might one day replace traditional glass in walls and roofs.

Maximizing natural light in buildings is popular because it can save energy.

However, traditional glass roofs and walls often cause problems like glare, lack of privacy, and overheating. Current solutions like coatings and light-diffusing materials haven’t fully solved these issues.

The new material developed by KIT researchers combines several useful properties. This polymer-based micro-photonic multi-functional metamaterial (PMMM) is made of tiny silicone pyramids, each about 10 micrometers wide—one-tenth the diameter of a hair.

These microscopic pyramids give the PMMM film multiple functions: light diffusion, self-cleaning, and radiative cooling while staying highly transparent.

A key feature of this material is its ability to release heat efficiently through the Earth’s atmosphere’s long-wave infrared transmission window. This means it can cool passively without using electricity, as explained by Professor Bryce S. Richards from KIT.

The researchers tested the material both in the lab and outside on the KIT campus. They measured its ability to let light through, scatter light, reflect light, clean itself, and cool down. The material achieved a cooling effect of 6°C below the surrounding temperature.

It also showed high transparency, allowing 95% of light to pass through, compared to 91% for regular glass. Additionally, the micro-pyramids scattered 73% of the incoming sunlight, creating a blurry appearance that reduces glare.

“When used in roofs and walls, this material creates bright, glare-free indoor spaces that also protect privacy. In greenhouses, its high light transmittance could boost plant yields, as the photosynthesis efficiency is estimated to be 9% higher than with glass roofs,” said Gan Huang, a Group Leader at KIT.

The micro-pyramids also make the PMMM film superhydrophobic, meaning water forms droplets and rolls off, taking dirt and dust with it. This self-cleaning property makes the material easy to maintain and durable.

“Our new material has great potential for various applications and significantly contributes to sustainable and energy-efficient architecture,” explained Richards.

This innovative material can optimize indoor sunlight use, provide passive cooling, and reduce the need for air conditioning. It is scalable and can be easily integrated into environmentally friendly building designs and urban development plans.

By using this material, we can create more comfortable, energy-efficient buildings while also helping the environment. The self-cleaning feature ensures that the material remains effective over time, making it a practical and sustainable solution for the future of construction.