The Karlsruhe Institute of Technology (KIT) in Germany has introduced a groundbreaking innovation: a self-cleaning metamaterial poised to revolutionize architectural design by potentially replacing conventional glass in walls and roofs. While glass enhances natural light penetration, it brings with it drawbacks such as glare, discomfort, privacy concerns, and heat retention, necessitating excessive air conditioning.
“This can adversely affect productivity and overall well-being, especially for individuals who work in environments with excessive sunlight or bright lighting,” according to the KIT researchers.
Enter PMMM (polymer-based micro-photonic multi-function metamaterial), the brainchild of KIT researchers. PMMM, featuring micro-pyramid surface structures, stands out as a superior alternative to glass. Unlike glass, which traps heat, PMMM facilitates radiative cooling by releasing heat as long-wave infrared radiation, thereby maintaining a cooler indoor environment even in sunlight.
“We introduced a polymer-based micro-photonic multi-function metamaterial (PMMM) with micro-pyramid surface structures that efficiently and simultaneously address the challenges faced by traditional glass materials,” the study authors note.
Lab and outdoor tests in Karlsruhe demonstrated PMMM’s remarkable cooling capabilities, with temperatures consistently lower than ambient conditions. Moreover, PMMM diffuses 73% of radiation, leading to softer, evenly distributed indoor lighting while enhancing privacy by reducing visibility from outside.
The researchers conducted lab and outdoor tests to check the cooling ability of their material. “Throughout the test, the temperature of the PMMM was consistently lower than the ambient temperature,” the researchers said.
For instance, “At 14:48, the PMMM temperature was ~6 °C lower than the ambient temperature, demonstrating significant cooling in the high-humidity environment of Karlsruhe (the German city where KIT is located),” they added.
“The micro-pyramid structures exhibit sunlight diffusing and minimize reflection losses through multiple reflections, resulting in a transparency of 95% for visible light, and an overall diffuse transmittance of 73%,” the study authors note.
A major advantage of PMMM over glass lies in its self-cleaning properties, akin to those observed in lotus leaves. The micro-pyramids induce water droplets to bead up, effectively sweeping away dirt and dust as they roll across the surface. This eco-friendly, commercially viable solution offers the promise of low-maintenance architectural materials.
“Leveraging the micro-pyramids’ resemblance to the micro-cones found on lotus leaves, our metamaterial also possesses superior superhydrophobic properties, facilitating self-cleaning capabilities.”
“This multi-functional metamaterial paves the way for sustainable green buildings with enhanced transparency, energy efficiency, and occupant well-being. It contributes to the ongoing efforts towards creating a more sustainable built environment,” the study authors said.