A New Eco-Friendly Cooling Film

An Inexpensive Passive Coating that Requires No Energy to Cool

Gerania bosci bosci (longhorn_beetle) on a coconut. | Credit: Basile Morin

A longhorn beetle, native to Southeast Asia, has yielded its secret for staying cool to a team of scientists from the University of Texas at Austin, Shanghai Jiao Tong University, and the KTH Royal Institute of Technology in Sweden. This beetle lives in some of the most inhospitable places on earth, on the edge of active volcanos where temperatures are regularly above 104 degrees Fahrenheit and the ground can get as hot as 158. Its ability to keep from being roasted alive at these temperatures lets it live where its competitors cannot.

The secret lies in tiny triangular structures on the beetle’s wings. The entire structure reflects light while the filler “fluff,” with its pleat-like microstructure, scatters sunlight and allows body heat to escape.


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In a quest to mimic this structure, biomimicry at its best, scientists have developed a photonic film, constructed from a common polymer, that is flexible, mechanically strong, water resistant, and easy to manufacture. The scientists embedded microscopic spherical ceramic particles in the polymer to scatter sun rays rather than absorb them, then stamped a micro-triangular pattern onto the film similar to that on the beetle’s wings. When placed in direct sunlight, objects beneath this film were as much as 9 degrees cooler than the same objects not covered by it.

The possibilities for this film are great: It can be applied to cool windows; it can protect solar panels from sunlight-induced degradation; it can keep cars cool while parked; it can cool electronic devices; and it can be applied to the fabrics of clothing. Other opportunities being pursued are as a part of water-cooling systems, as desert dew-water harvesting devices, and as supplemental cooling systems for power plants.

Refrigeration systems are some of the biggest consumers of energy. The U.S. Energy Information Administration projects a significant jump in air-conditioning consumption by 2050 — a 59 percent increase in residential use and a 17 percent rise in commercial demand. Because this film provides passive cooling — it requires no energy to operate — it can save huge amounts of money and reduce taxing the environment. It can be applied as a coating to a great many objects, to almost anything, in fact. Moreover, because the materials and processes used to fabricate the film are already widely available and inexpensive, it should be easy to scale up for mass production.


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