Ultrathin flexible heat pipes with heat transfer performance and flexibility optimization for flexible electronic devices

Abstract

Ultrathin flexible heat pipes (UFHPs) are considered an ideal solution to the heat dissipation problem of flexible optoelectronics. However, the relatively poor heat transfer performance and flexibility of UFHPs greatly limit their application. In this study, laser ablation and embossing were adopted to optimize the comprehensive performances of UFHPs. The laser ablation removed the oxidized Nylon layer of the casing to reduce its thermal resistance, and the embossing process generated corrugated structures on the casing to enhance flexibility. The experimental results showed that removing the oxidized Nylon layer increases the thermal conductivity of UFHPs by 44.2–67.2 %, and the maximum thermal conductivity of UTHPs with a thickness of 0.63 mm reached 2423.7 W/m·K under forced water cooling conditions. The thermal conductivity could be further improved considering the casing still has polymer layers with a total thickness of 35 μm. Additionally, the thermal conductivity attenuation rates of UFHPs after repeated bending 50 times decreased from 73.2 % to 11.8 % when corrugated structures were applied. Under natural convective conditions, UFHPs with optimized design decreased the heater temperature by 11.7–16.1 % compared to the 0.7 mm copper plate. Further, they exhibited a consistent temperature distribution even after being bent 50 times. The corrugated structures reduced the elastic modulus of the casing, which avoided the formation of wrinkles during repeated bending and ensured the low resistance flow of vapor. The optimization techniques explored in this study offer a promising framework for enhancing and manufacturing high-performance UFHPs to meet the growing demands for heat dissipation in advanced optoelectronics.