Thermally conductive and optically transparent flexible films with surface-exposed nanocellulose skeletons

Abstract

Heat management has become a serious bottleneck that has limited the development of thin flexible paper electronics. Therefore, there is a huge demand to develop superior flexible film materials with higher thermal conductivities and transparencies. In this study, thermally conductive and optically transparent flexible films with flexible nanocellulose skeletons have been fabricated by using a membrane-assisted method. The films simultaneously exhibit in-plane thermal conductivity as high as 2.5 W m⁻¹ K⁻¹ with a thermal conductivity enhancement of 234% from the matrix acrylic resin, and a parallel beam transmittance of 73% at 600 nm. We demonstrate that removal of heat-insulating surface resin layers achieved by our membrane-assisted method is the key to exploit the high thermal performance of intrinsic nanocellulose skeletons with a markedly high fiber content of ∼80%. The thermal and optical properties of membrane-assisted films are controlled by changing the fiber content. We believe that this approach could provide a way to solve the critical bottleneck of modern electronics by advanced thermal management.