Bioinspired cellulose aerogel mimics white beetles for passive daytime cooling

Passive daytime radiative cooling has emerged as a promising strategy for reducing building energy consumption without additional electricity input. By reflecting solar radiation while simultaneously emitting thermal energy into outer space through the atmospheric infrared window, these materials can passively lower surface temperatures even under direct sunlight. However, achieving both high solar reflectance and high infrared emissivity in a single material remains difficult, particularly when scalable and environmentally friendly fabrication routes are required.

In a recent study, researchers developed a cellulose-based cooling aerogel inspired by the optical structure of white beetles, insects known for maintaining relatively low body temperatures under intense sunlight because of their unique disordered micro/nanostructures. Rather than simply copying the beetle’s appearance, the study focused on reproducing its multi-scale light-scattering mechanism through a carefully engineered porous architecture.

The cooling aerogel was constructed using nanofibrillated cellulose, cellulose nanocrystals, and MOF-801, a hygroscopic metal-organic framework capable of regulating water interactions during freezing. During directional freeze-casting, the MOF particles absorbed water molecules and altered the kinetics of ice nucleation, allowing cellulose fibers and nanoparticles to self-assemble into a hierarchical network composed of nanoscale particles, microscale fibers, and interconnected macropores. According to the authors, this hetero-photonic scattering topology significantly enhanced broadband sunlight scattering across the solar spectrum.

Optical measurements showed that the optimized aerogel achieved a solar reflectance of 95.8% and an infrared emissivity of 95%. Finite-difference time-domain simulations further confirmed that the hierarchical structure provided stronger scattering efficiency than conventional porous structures. Under outdoor sunlight conditions, the material achieved daytime subambient cooling of up to 7.1 °C. Infrared imaging also demonstrated that the aerogel maintained lower surface temperatures compared with conventional nanocellulose aerogels under solar irradiation.

Beyond optical performance, the researchers emphasized the environmental advantages of the material system. The aerogel is based primarily on cellulose, showed good biodegradability in soil within 21 days, and exhibited lower environmental impacts than conventional petroleum-based foams according to life-cycle assessment analysis. The material also retained strong optical performance after prolonged ultraviolet exposure, indicating good outdoor durability.

To evaluate practical application potential, the team conducted building energy simulations using EnergyPlus software. The results suggested that buildings coated with the cooling aerogel could reduce annual cooling energy consumption by approximately 43.5% on average in many regions of China, with the strongest effects observed in hot and densely populated southern areas. The authors believe the combination of passive cooling performance, sustainability, and scalable fabrication could make the material attractive for future energy-saving building technologies.

See the article:

DOI

https://doi.org/10.1016/j.jobab.2026.100267

Original Source URL

https://www.sciencedirect.com/science/article/pii/S2369969826000393

Journal

Journal of Bioresources and Bioproducts