In developing countries, storing agricultural produce is often difficult: Heat and drought cause fruits and vegetables to spoil quickly – a problem especially for smallholder farmers who cannot afford refrigeration equipment or have no access to electricity. A "cooling blanket" from Empa's Laboratory for Biomimetic Membranes and Textiles in St. Gallen could provide a solution. It harnesses the cold produced when water evaporates – with the help of a low-cost material that is available everywhere: Charcoal can absorb a lot of water thanks to its high porosity, enabling efficient evaporation.

To use the charcoal, the researchers constructed their blanket with vertical tubes that are filled with pieces of charcoal. This creates self-supporting, malleable "walls" that are doused with water – and evaporation cools the space inside. In analyses in the lab, the temperature dropped by about five degrees in a moderately humid environment.

In drier and warmer climates, the researchers say, it could drop by ten degrees or more. At the same time, the humidity inside rose significantly – a natural protection against wilting. With this experience, the researchers now want to develop a pilot plant and test it in Africa or Asia. At the same time, they are working on a business model that will make it easier for smallholder farmers to adopt and introduce the technology.