Enhanced Thin-Film Boiling in Filamentous Graphene Heat Sinks Synergized with Passive Liquid Supply

Abstract

Graphene heat sinks hold great application potential in the field of high-efficiency thermal management. However, the complex fabrication of graphene and its intrinsic hydrophobicity limit its efficiency in enhancing boiling heat transfer. Herein, this study employs polyimide (PI) as the precursor to develop a heat sink with a laser-induced NaOH-activated graphene (LIAG) structure, which achieves thin-film boiling heat transfer via a passive liquid supply method. Under atmospheric pressure, with water as the working fluid and a heating area of 1 cm², the critical heat flux (CHF) of this LIAG heat sink reaches 99.3 W/cm², which is 5 times that of the bare PI. The maximum heat transfer coefficient (HTC) reaches 2.46 W/(cm²·K), which is 7.7 times that of the bare PI. And the superhydrophilic LIAG micronano fibrous structure enables the maintenance of efficient thin-film boiling with low working fluid consumption, while the passive side liquid supply method eliminates the energy consumption associated with pumping. It was also verified that the equivalent thermal conductivity (ETC) of LIAG applied in ultrathin heat transfer devices can reach 1923.35 W/(m·K). The LIAG-based thin-film boiling heat transfer strategy proposed in this study provides a reference direction for high-power electronic devices cooling.

Keywords: enhanced heat transfer; graphene heat sink; laser preparation; passive liquid supply; thin-film boiling; ultrathin heat transfer device.