Learning from camels
Stephen Barnes / Animals / Alamy
A thin layer of gel that mimics camel skin could help insulate items and potentially keep them cool for days without electricity.
Researchers have long been interested in hydrogels that can absorb water and then release it through evaporation to achieve a passive cooling effect without electricity. A key challenge, however, was to find ways to keep this effect longer.
Jeffrey Grossman of the Massachusetts Institute of Technology and his colleagues sought inspiration for camels by combining hydrogel with a thin layer of another gel – – Airgel – – It is a light, porous insulating material.
“Our double evaporation insulation layer mimics the camels,” says Grossman.
The hydrogel layer is like the camel’s sweat gland, allowing the water to evaporate and providing a cooling effect, while the airgel layer plays the same role as the camel’s coat.
“We achieve evaporation and isolation at the same time and thus extend the cooling time considerably,” says Grossman. Overall, the double gel layer is around 10 millimeters thick.
The researchers tested their two-layer gel in a temperature and humidity controlled chamber in the laboratory. It was able to cool an object to 7 ° C below ambient and keep it cool longer compared to a single layer of hydrogel.
The team found that adding the airgel layer resulted in an effective cool-down time five times longer than the hydrogel layer alone. “This corresponds to a cooling time of over 250 hours,” says Grossman – that corresponds to around 10 days.
“We are working on making the materials more scalable to pave the way for wider adoption of this technology,” says Grossman. He says the gel bilayer could have uses to keep food or medical supplies cool and to cool buildings to reduce their energy use.
Journal reference: Joule, DOI: 10.1016 / j.joule.2020.10.005
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