Radiative Revelations & Reflective Resilience

A novel biodegradable film made from polylactic acid, a plant‑derived bioplastic, has been shown to passively reflect nearly all incoming solar radiation while allowing building heat to radiate out to space. In experiments, this "metafilm" reduced surface temperatures by as much as 9.2 °C under peak sunlight and maintained an average cooling effect of about 4.9 °C during the day and 5.1 °C at night. Its performance was described in Cell Reports Physical Science.

Electrically Eliminated & Energy Exhaled

Unlike conventional cooling systems, which consume electricity and release CO₂, this film operates without any power source or mechanical components. It uses radiative cooling, a natural process where heat is radiated into the cold universe. This makes it not only energy‑efficient but also eco‑friendly, potentially reducing carbon emissions linked to air conditioner usage in cities.

Stellar Solar Scattering & Nighttime Nadir

The film achieves its cooling effects through dual mechanisms: near-total solar reflectance and effective thermal emissivity in the mid‑infrared spectrum. By reflecting over 98% of sunlight and emitting heat at night, it ensures that building surfaces stay cooler than the ambient air. This enables passive cooling even on hot, sunny days, reducing dependency on artificial climate control.

Durable Design & Degradation Discipline

Beyond laboratory conditions, the metafilm endured 120 hours of strong acid exposure and simulated eight months of ultraviolet radiation, yet retained a 6.5 °C cooling effect. Unlike many passive‑cooling coatings that degrade quickly, this biodegradable PLA film remains robust in harsh environments, maintaining its cooling capabilities over time.

Eco‑Elegance & Environmental Endurance

PLA is fully biodegradable and breaks down into water‑soluble components rather than microplastics. Dr Xianhu Liu of Zhengzhou University emphasised the film’s sustainability: it offers high solar reflectance and thermal emission, yet remains environmentally benign. This positions it as a superior alternative to traditional cooling materials like ceramic coatings or petrochemical‑based polymers.

Scaling Smartly & Simulation Support

Researchers confirmed its feasibility for large‑scale applications and real‑world deployment. Simulations show buildings in hot climates, such as Lhasa, could see annual energy savings exceeding 20%. This underscores the film’s potential to mitigate urban heat islands, reduce energy consumption, and provide climate resilience at scale.

Manufacturing Method & Market Mobilisation

The metafilm is produced through a low‑temperature separation process, allowing for efficient manufacturing and minimal energy use. With its scalable production capability, the technology could soon be commercialised. Potential uses extend beyond architecture to transport, electronics, agriculture, and even medical applications like cooling wound dressings.

Paradigm Shift & Passive Potential

This innovation marks a new era in passive cooling, electricity‑free, biodegradable, and scalable. Especially as heatwaves intensify globally, the technology offers a promising, low‑cost tool for cooling buildings, reducing energy consumption, curbing emissions, and boosting human comfort without straining power grids.

4. Key Takeaways:

• PLA‑based passive cooling film reduces surface temperatures by up to 9.2 °C and averages 4.9 °C daytime and 5.1 °C nighttime cooling

• Can lower annual building energy consumption by over 20% in hot climates, while remaining durable after acid and UV exposure

• Biodegradable into water‑soluble compounds, the film avoids microplastic pollution and offers a sustainable climate‑resilient coating