Diameter Dependence (IMAGE) Science China Press Caption (a) The diameter dependence of the thermal conductivity of polyimide nanofibers. The rhombus represents experiment data. There is a dimensional crossover of heat diffusion in molecular chains from quasi-1D to 3D. (b) Schematic of anisotropic quasi-1D thermal diffusion in nanofibers with small diameters. All the molecular chains are aligned along the fiber axis. The blue arrow denotes the 'random walk' of heat carriers within the chain. (c) Schematic of the quasi-isotropic thermal diffusion in nanofibers with large diameters. The molecular chains are randomly oriented and entangled with each other. Heat carriers could 'jump' to another chain as the red arrow denoted. Credit ©Science China Press Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.