3D Printed Liquid Crystal Polymer Thermosiphon for Heat Transfer under Vacuum

A novel approach is presented to 3D print vacuum-tight polymer components using liquid crystal polymers (LCPs). Vacuum-tight components are essential for gas storage and passive heat transfer, but traditional polymer 3D printing methods often suffer from poor interfaces between layers and high free volume, compromising vacuum integrity. By harnessing the unique properties of LCPs, including low free volume and low melt viscosity, highly ordered domains are achieved through nematic alignment of polymer chains. Critical gas-barrier properties are demonstrated, even in thin, single-print line-walled samples ranging from 0.8 to 1.6 mm. A 200 mm evacuated thermosiphon is successfully printed, which exhibits a thermal resistance of up to 2.18 K/W and an effective thermal conductivity of up to 28 W/mK at 60 degrees C. These values represent a significant increase compared to the base LCP material. Furthermore, the geometric freedom, enabled by 3D printing through the fabrication of complex-shaped thermosiphons, is showcased. The authors study highlights the potential of LCPs as high-performance materials for 3D printing vacuum-tight components with intricate geometries, opening new avenues for functional design. An application of integrating 3D printed thermosiphons as selective heat transfer components in building envelopes is presented, contributing to greenhouse gas emissions mitigation in the construction sector.