Negative-defocused laser-induced activated graphene with nanofibrous structure for enhanced capillary performance and thermal management

• A negative-defocus strategy of nanofibrous laser-induced graphene fabrication. • Nanofibrous structure achieved the highest reported capillary height and velocity. • Capillary height reaches 120 mm in 46 s, with a wicking velocity of 21.71 mm·s -0.5 . • Ultrathin vapor chamber achieves thermal conductivity of 1225.6 W/(m·K) Laser-induced activated graphene (LIAG) structures have been widely utilized in emerging fields such as supercapacitors, flexible sensors, and wastewater treatment. However, traditional LIAG structures are typically characterized by a reticulated porous morphology, and their inferior capillary rise performance has emerged as a critical constraint limiting their applicability across diverse domains. To address this limitation, we developed a unique negative-defocus strategy to fabricate a novel nanofibrous laser-induced activated graphene (FLIAG) structure on NaOH-coated polyimide films, which represents a functional morphology with superior capillary performance in LIAG fabrication. This unconventional manufacturing strategy enables precise control over the formation of LIAG structures, thereby breaking the intrinsic capillary limitations of traditional reticulated porous structures. The resulting FLIAG achieved a full sample capillary rise height of 120 mm within 46 s and a wicking velocity of 21.71 mm·s −0.5 , representing a 115.7% improvement over traditional structures and the highest performance reported to date for LIAG-based materials. Furthermore, a 0.5 mm-thick ultrathin vapor chamber with FLIAG wick achieved an effective thermal conductivity of 1225.6 W/(m·K), nearly three times that of copper. These findings highlight the potential of FLIAG for efficient thermal management applications, while also offering a viable technical option for interfacial solar steam generation, wastewater treatment, and other relevant fields where extreme capillary performance is demanded.