Scalable 3D Thermal Conductivity Architecture of Polyethylene Film via Hot Pressing of Oriented Fibers

Polymeric materials with 3D high thermal conductivity are desired but challenging. In this work, a strategy is proposed to manipulate the orientation of molecular chains and thermal conductivity of polyethylene (PE) film via hot pressing of highly oriented fibers. After hot‐pressing, molecular chains in fibers remain oriented; hence, the thermal conductivity in three dimensions can be architected by freely pre‐weaving. With the approach, PE film is obtained with thermal conductivity of 12, 5, and 0.25 W m −1 ·K −1 in three dimensions, respectively. The thickness can be as high as ≈700 micrometers, which is more applicable than ultrathin films for manufacturing and thermal management. Applying the PE film as a soaking plate on a simulated smartphone, the PE film reduces the temperature of the chip by 24.7 °C, showing the potential of the approach in rational design and large‐scale assembling of thermally conductive, electrically insulating, flexible, and lightweight polymers for thermal management applications.