A group led by Professor Son Kyun Kim of the Department of Physics and Chemistry at the Daegu Gyeongbuk Institute of Science and Technology (DGIST, South Korea) has developed a flexible film for passive cooling of electronics. The material requires no water or electricity: it absorbs moisture from the air, and when the device heats up, the moisture evaporates and carries away heat. The results were published in the journal Small Structures.
The growth in the number of data centers for artificial intelligence, the heating of mobile devices and electric vehicle batteries are worsening the cooling problem. Traditional active systems with pumps and fans consume energy and water, and their maintenance is expensive. The alternative is passive cooling with no external costs. But most known moisture-absorbing materials are rigid crystalline solids. They adhere poorly to the surfaces of electronics and cause corrosion, which hinders their mass adoption.
Kim's team combined nanocellulose (a natural material that retains moisture well) with organic ionic molecules that actively absorb water. The result was a flexible and adhesive film. It maintains strong adhesion and elasticity even in a completely dry state, so it fits tightly against metal, semiconductors and glass without gaps. Even in a dry environment, the material accumulates a noticeable amount of moisture from the air. When the device heats up, it evaporates and lowers the surface temperature in real time. Importantly, the film does not cause corrosion, so it can be applied directly, without an additional coating.
In tests during continuous operation of electronics, the film steadily lowered the device surface temperature by up to 18.2 °C - from 72.3 °C to 54.1 °C - for more than 12 hours in a row. This is a laboratory result, not a characteristic of a finished commercial product.
"The significance of this work goes beyond the creation of an eco-friendly material. It simultaneously removes several limitations of previous passive cooling materials, including corrosiveness, insufficient flexibility and weak adhesion," Kim explained.
The authors emphasize that this is about solving heat dissipation problems in confined spaces, not a ready-to-sell technology. Further steps are testing on real devices and scaling up.