Researchers develop bioplastic metafilm for cooling

Researchers from Zhengzhou University in China and the University of South Australia (UniSA) have developed a bioplastic metafilm that can be applied to buildings, equipment and other surfaces, passively cooling temperatures by as much as 9.2°C during peak sunlight and reflecting almost 99% of the sun’s rays.
 
According to the research team, the new film is a sustainable and long-lasting material that could reduce building energy consumption by up to 20% a year in some of the world’s hottest cities.
 
The research paper introducing the metafilm was published the latest issue of Cell Reports Physical Science.

Combatting global warming

UniSA PhD candidate Yangzhe Hou, who was part of the research team, says the cooling metafilm represents a breakthrough in sustainable materials engineering that could help combat rising global temperatures and hotter cities.
 
“Our metafilm offers an environmentally friendly alternative to air conditioning, which contributes significantly to carbon emissions,” says Hou, who is also from Zhengzhou University.
 
“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.”
 
Notably, the film continues to perform even after prolonged exposure to acidic conditions and ultraviolet light – two major barriers that have historically hindered similar biodegradable materials.

A natural solution

Constructed from polylactic acid (PLA) – a common plant-derived bioplastic – the metafilm is fabricated using a low-temperature separation technique that reflects 98.7% of sunlight and minimises heat gain.
 
“Unlike conventional cooling technologies, this metafilm requires no electricity or mechanical systems,” says co-author Dr Xianhu Liu from Zhengzhou University.
 
“Most existing passive radiative cooling systems rely on petrochemical-based polymers or ceramics that raise environmental concerns. By using biodegradable PLA, we are presenting a green alternative that offers high solar reflectance, strong thermal emission, sustainability, and durability.”
 
In real-world applications, the metafilm showed an average temperature drop of 4.9°C during the day and 5.1°C at night. Field tests conducted in both China and Australia confirmed its stability and efficiency under harsh environmental conditions. Even after 120 hours in strong acid and the equivalent of eight months’ outdoor UV exposure, the metafilm retained cooling power of up to 6.5°C.

Energy saving possibilities

Perhaps most significantly, the simulations revealed that the metafilm could cut annual energy consumption by up to 20.3% in cities such as Lhasa by reducing dependence on air conditioning.
 
“This isn’t just a lab-scale success” says co-author Professor Jun Ma from the University of South Australia.
 
“Our film is scalable, durable and completely degradable,” he says.
 
“This research aims to contribute to sustainable development by reducing reliance on fossil fuels and exploring feasible pathways to improve human comfort while minimising environmental impact.”
 
The discovery addresses a major challenge in the field: how to reconcile high-performance cooling with eco-friendly degradation.
 
The researchers are now exploring large-scale manufacturing opportunities and potential applications in buildings, transport, agriculture, electronics, and the biomedical field including cooling wound dressings.

Image courtesy of wirestock via Freepik

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