Construction of Vertically Interconnected Microdiamond Channels Inspired by Subcutis for Thermal Conductivity Enhancement of Polymer Composite Films

Polymeric composites with enhanced thermal conductivity are essential components for thermal management. Inspired by the stacked structure of adipose cells in the subcutis, we propose a strategy to construct a spatially interconnected thermal channel of microdiamonds (MDs) along vertical directions. In detail, a thermoplastic polyurethane (TPU)@MD core–shell structure was assembled via a microcladding method, which is utilized as reinforcement to fabricate the TPU@MD/poly(vinyl alcohol) (PVA) composite films through a doctor-blade coating technique. The resultant composite films exhibit a high through-plane thermal conductivity of 3.31 W/mK at a MD loading of 39 vol %, which is 195% higher than randomly dispersed composites. A two-step mathematical model was derived by the thermal resistance method to simultaneously analyze the mechanism of thermal conductivity enhancement. Meanwhile, the TPU@MD/PVA composites also reveal low dielectric loss. It is believed that this strategy to design and fabricate thermal interface materials with excellent properties provides effective guidance in thermal management applications.