Kirigami-processed cellulose nanofiber films for smart heat dissipation by convection

Kojiro Uetani,Yintong Huang,Masaya Nogi,Rikuya Watanabe,Jiahao Wang,Keitaro Kasuya,Toshifumi Satoh,Shota Tsuneyasu,Hirotaka Koga

doi:10.1038/s41427-021-00329-5

Abstract

Heat dissipation has become increasingly important in electronics. Conventional convection cooling systems have significant material and dimensional constraints, and they have difficulty meeting the heat dissipation, miniaturization, and flexibility requirements of next-generation smart electronics. Here, we used kirigami (the traditional art of paper cutting) with a thermally conductive cellulose nanofiber film to propose a flexible cooling system through convective heat dissipation. By stretching the Amikazari (net decoration) pattern produced by kirigami and allowing air convection through its aperture at 3.0 m/s, the thermal resistance was reduced to approximately one-fifth of that without kirigami and convection. The kirigami apertures defined the outlet air velocity, resulting in a significant increase in the heat-transfer coefficient. Our kirigami heat dissipation concept enables the design of electronics using a variety of film materials as shape-variant cooling structures, which will inspire a wide range of thermal engineering and electronics applications.

Highlights

Heat dissipation systems play an important role in preventing the thermal runaway of electronic devices with ever-increasing exhaust heat, ensuring normal operation and safety, and determining the design freedom of electronic devices
Unlike most of the above applications that focus on stretching dynamism and metamaterial designability for future 4D electronics, here, for the first time, we focus on the periodic void structure of kirigami that enhances interaction with air and forms an effective convection path
Preliminary experiments showed that the tunicate cellulose nanofibers (T-CNFs) film with abundant carboxyl groups introduced on the CNF surface showed extended burning along the processed lines, suggesting that cellulose degradation was in progress even outside the pattern line

Summary

Introduction

Heat dissipation systems play an important role in preventing the thermal runaway of electronic devices with ever-increasing exhaust heat, ensuring normal operation and safety, and determining the design freedom of electronic devices. Conventional cooling systems use convection to transfer the heat from a heat source to a convecting fluid. While this provides high cooling performance, it requires heat sinks with many metal/ceramic fins, as well as thermal interface materials[2] to improve adhesion and thermal conduction with hard heat sources. While a system that diffuses heat throughout the substrate and housing by thermal conduction is expected to make the entire electronic to be thinner and more flexible than when using heat sinks, it requires a large area and a composite material with high thermal conductivity to provide sufficient cooling[4,5,6,7], which leads to larger components and less flexibility. A heat dissipation mechanism that maintains flexibility is needed for the development of next-generation highperformance multifunctional devices

Methods

Results

Conclusion