Innovative material for passive cooling and natural lighting

Researchers at the Karlsruhe Institute of Technology have developed a polymer-based material that is more transparent to light than regular glass and maintains a comfortable indoor temperature. 

Glass roofs and walls are typically used to maximise natural light in buildings and allow energy savings.

Researchers at the Karlsruhe Institute of Technology (KIT) have developed a novel polymer-based material that could replace glass components. Known as a Polymer-based Micro-photonic Multi-functional Metamaterial (PMMM), this material consists of microscopic pyramids made of silicone. Each micro-pyramid measures about ten micrometres, which is about one-tenth the diameter of a human hair. The material takes the form of a thin film that can be stuck onto a pane of regular glass.  


The PMMM film has several functions. 

  • Radiative cooling 

In the lab and in real outdoor experimental conditions, the material achieved cooling of 6°C compared to the ambient temperature. 


  • Light diffusion while maintaining a high level of transparency. 

The PMMM scatters 73% of incoming sunlight, which gives the material a frosted or blurry appearance. Despite this, it is more transparent to light than regular glass, offering 95% transmittance compared to the usual 91% of most glasses. According to the research team, the high light transmittance could increase yields in greenhouses,as photosynthesis efficiency is estimated to be 9% higher than in glass-roofed greenhouses. 


  • Self-cleaning 

The micro-pyramids give the PMMM film superhydrophobic properties, similar to those of a lotus leaf: water beads up in droplets and removes dirt and dust from the surface. 


For more information, visit the Karlsruhe Institute of Technology (KIT) website.


The researchers have published an open access paper in Nature Communications.



Did you know? The IIR has published an Informatory Note on passive cooling, available on FRIDOC.  


Image credits: Gan Huang, Karlsruhe Institute of Technology (KIT)