Tree-inspired and scalable high thermal conductivity ethylene-vinyl acetate copolymer/expanded graphite/paraffin wax phase change composites for efficient thermal management

Bioinspired fabrication of high thermal conductivity phase change composites has great prospects for efficient thermal management. However, the direct and partial imitations of nature are not facile to the full realization of natural systematic advantages and scalable production. Herein, inspired by the tree's transportation system, this study adopted a bottom-up strategy to mimic the tree's sophisticated hierarchy at both micro and bulk di-mensions. The composites employed a phloem-mimic crosslinking ethylene-vinyl acetate copolymer/paraffin wax (EVA/PW) film as the intelligent heat storage and release medium, and the xylem-imitated roll-to-roll directional EVA/expanded graphite (EVA/EG) film with enhanced high thermal conductivity (51.1 W m-1 K-1 with the enhancement of 26,894 %) as fast heat conduction pathway. Above two components were assembled to develop phase change composites (PCCs) with annual-ring and multilayered structures. Both computational and experimental results revealed that the assembled tree-inspired structures significantly improve the heat con-duction performances of PCCs. The tree-inspired PCCs showed significantly high thermal conductivity (7.01 W m- 1 K-1 with the enhancement of 2821 %) with a low filler content (9.0 vol%). Meanwhile, obtained PCCs with high phase change enthalpy exhibited excellent temperature regulation performance. This work offers a prom-ising route for the scalable manufacture of advanced PCCs for efficient thermal management, and a general strategy to realize the natural systematic advantages via the bottom-up strategy.