Review on the fabrication of surface functional structures for enhancing heat transfer of heat pipes

Heat pipes, as efficient two-phase heat-transfer devices, are widely applied in thermal management of electronics for their remarkable thermal conductivity and high reliability. However, the development of high-performance, miniaturization and high-density packaging of electronics demands a solution to thermal management of large heat flux in limited space, which requires heat pipes with stronger heat transfer performances. As the core component of heat pipes, wick provides the capillary pressure to drive the closed circulation of the working fluid and an interface for the liquid–vapor phase changes, which determines the start-up performance and heat transfer capacity of heat pipes. Capillary pressure of wicks and thermal performance of heat pipes can be enhanced by fabricating functional structures on the surface of wicks. This paper presents a comprehensive review on the recent developments and applications of surface functional structures of heat pipe wicks. The applications of heat pipes with different wick structures are introduced, and the manufacturing technologies of surface functional structures are summarized and compared. Furthermore, the fabrication of surface functional structures used for various wicks are reviewed and analysed in detail. Finally, the challenges affecting the development of surface functional structures are outlined, and recommendations for future research are presented.