Scientists have demonstrated an ultra-efficient passive convective cooling technology using cellulose nanofiber film based on kirigami, a traditional Japanese paper folding art similar to origami. The difference from origami is that in addition to folding, kirigami uses paper cutting.
A new development by scientists from SANKEN (Institute for Scientific and Industrial Research) at Osaka University, Oita National College of Technology and Tokyo Polytechnic University, could allow small, flexible electronic devices to operate without overheating.
As computer makers try to cram more and more transistors into their tiny gadgets, the problem of excess heat dissipation is becoming increasingly important. Traditional passive cooling systems that use convective airflow around metal heat sinks are often cumbersome and rigid. But many small wearable electronic devices will soon be able to rely on cheaper and more flexible heat dissipation methods.
A team of researchers led by Osaka University has found that a film of treated cellulose nanofibers carved in a kirigami style can significantly improve cooling. The scientists used a simple kirigami pattern called amikazari, but "stretched" it. The slits in the film can open to form wide holes through which air can flow.
Applying laser technology to cut the holes in a traditional pattern, the team conducted a heat dissipation test, noticing a dramatic difference in maximum temperature between the kirigami film and a similar cool-down with uncut film.
In particular, this research could help design the next generation of wearable devices, as they pose challenging challenges with respect to the bulkiness and flexibility of cooling materials.
Illustrations: Kojiro Uetani et al, NPG Asia Materials