World’s first biodegradable cooling film drops energy use by 20% without electricity

UniSA PhD candidate Yangzhe Hou, who co-developed the material and is also affiliated with Zhengzhou University, called the metafilm “an environmentally friendly alternative to air-conditioning, which contributes significantly to carbon emissions.”

He explained that “the material reflects nearly all solar radiation but also allows internal building heat to escape directly into outer space. This enables the building to stay cooler than the surrounding air, even under direct sunlight.”

Powerless cooling with high efficiency

The metafilm is made from polylactic acid (PLA), a biodegradable plastic derived from plant sources such as corn or sugarcane. Using a low-temperature separation technique, the researchers created a porous, bi-continuous structure that reflects 98.7 percent of sunlight. The resulting cooling effect reached a peak of 9.2°C during midday sun, with consistent average drops of 4.9°C in the daytime and 5.1°C at night.

During performance testing, the film demonstrated cooling power up to 136 watts per square meter under direct sunlight. It also exhibited ultra-low thermal conductivity, just 0.049 W/m·K, thanks to its 84.6 percent porosity.

Durable and weather-resistant design

Unlike earlier biodegradable cooling materials that failed in real-world environments, this metafilm retained its performance even under extreme conditions. The research team exposed it to 120 hours in a strong acid solution and simulated eight months of outdoor UV exposure.

The material continued to deliver cooling effects of up to 6.5°C below ambient temperature.

Dr. Xianhu Liu from Zhengzhou University emphasized the innovation’s eco-conscious foundation. “Most existing passive radiative cooling systems rely on petrochemical-based polymers or ceramics that raise environmental concerns,” he said. “By using biodegradable PLA, we are presenting a green alternative that offers high solar reflectance, strong thermal emission, sustainability, and durability.”

The film’s robustness comes from its internal structure, particularly its 29.7 percent stereocomplex crystal content.

This feature enhances thermal and chemical stability, a key limitation in previous materials.

Lower energy costs for urban cooling

Computer simulations suggest that cities such as Lhasa, China, could cut annual cooling energy use by up to 20.3% by applying the metafilm to rooftops and other structures. The team believes this impact could scale globally, especially in regions with high heat and dense urbanization.

Professor Jun Ma from the University of South Australia noted the broader implications: “This isn’t just a lab-scale success. Our film is scalable, durable and completely degradable.”

Future-ready applications

Beyond buildings, the metafilm could benefit a range of industries. Researchers are exploring applications in transportation, agriculture, and electronics. Biomedical uses are also being considered, such as temperature-regulating wound dressings.

The fabrication process is relatively simple. PLA is dissolved in chloroform, then crystallized at –20°C. Ethanol is added to induce phase separation before drying the film into its final form. This method is suited to large-scale production, enhancing its commercial potential.

As global temperatures rise and energy demands surge, this biodegradable cooling solution may offer a clean, scalable alternative to traditional cooling technologies.

The study is published in Cell Reports Physical Science.