High-performance ultra-thin thermal ground plane based on parallel liquid-vapor paths using hierarchical wicking structures

Abstract

Ultra-thin thermal ground plane (UTTGP), based on liquid-vapor phase-change heat transfer, is potential to meet the increasing thermal management demands of portable electronic devices. Conventional UTTGPs below 0.4 mm based on stacked liquid-vapor paths suffer from highly increased liquid-vapor flow resistance due to the decreased thickness, leading to both low maximum heat transfer powers less than 4 W, and high thermal resistances exceeding 2 K/W. Here, we invent a high-performance UTTGP with thickness of only 0.25 mm based on parallel liquid-vapor paths with out-of-plane hierarchical wicking structures. In this proposed UTTGP, vapor channels are placed between regular intervals of liquid wicking paths to maximize the thickness space for vapor flowing with low resistance. Liquid wicking paths are composed of hierarchical structures with micro-pillar array and spiral mesh etched with nanoscale grasses, leading to both high permeability and high capillary pressure to strengthen liquid transport. Thus, this new-type UTTGP simultaneously achieves a maximum heat transfer power of 6.5 W, a low thermal resistance of 0.98 K/W, a high effective thermal conductivity of 9259 W/(m·K) and good cyclic stability. This efficient UTTGP stands out in the comparison of heat transfer performance with the literature and offers a reliable and efficient solution for thermal management in space-constrained high-power portable electronics.