A Fully 3D-Printed Flexible Polymeric Heat Pipe

Advancements in flexible electronics demand innovative thermal management solutions that are both flexible and efficient. A fully 3D-printed polymeric heat pipe with high flexibility and low cost was demonstrated in this study. This wickless gravity-assisted heat pipe was fabricated using a commercial stereolithography 3D printer and soft elastomer. An interconnected pocket array was designed to reduce the wall thickness to 0.1 mm. The post-cured heat pipe can be flexed and twisted without tearing or permanent deformation. Experimental studies were conducted to characterize the performance of the heat pipe in vertical and 90-deg flexed configurations. In addition, high-speed imaging was applied to visualize the boiling process within the heat pipe. By charging with a compatible dielectric fluid HFE-7100, the present heat pipe achieved 18.6 W heat dissipation over a hot spot with an area of 25 × 25 mm², representing about 125% higher heat flux than most reported fully polymeric heat pipes using the same working fluid. When placed vertically, the result showed an effective thermal conductivity of up to 102.7 W/(m · K). The visualization indicated little difference in bubble dynamics between the vertical and flexed configurations owing to a high charging mass. The heat pipe startup occurred at 5.4 W, and no dryout was observed within the test range for either configuration. Finally, a comparison of the present study and other reported fully polymeric flexible heat pipes was made, and future optimization of the heat pipe performance was discussed.