Chun Jiang, Xu Chen, Li Qifan, Chen Yansong, Zhao Qishan, Yang Wei, Wen Rongfu, Ma Xuehu
State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory of Clean Utilization of Chemical Resources, Institute of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
Langmuir. 2022 Jan 11;38(1):352-362. doi: 10.1021/acs.langmuir.1c02647. Epub 2021 Nov 23.
Numerous studies have focused on designing micro/nanostructured surfaces to improve wicking capability for rapid liquid transport in many industrial applications. Although hierarchical surfaces have been demonstrated to enhance wicking capability, the underlying mechanism of liquid transport remains elusive. Here, we report the preferential capillary pumping on hollow hierarchical surfaces with internal nanostructures, which are different from the conventional solid hierarchical surfaces with external nanostructures. Specifically, capillary pumping preferentially occurs in the nanowire bundles instead of the interconnected V-groove on hollow hierarchical surfaces, observed by confocal laser scanning fluorescence microscopy. Theoretical analysis shows that capillary pumping capability is mainly dependent on the nanowire diameter and results in 15.5 times higher capillary climbing velocity in the nanowire bundles than that in the microscale V-groove. Driven by the Laplace pressure difference between nanowire bundles and V-grooves, the preferential capillary pumping is increased with the reduction of the nanowire diameter. Capillary pumping of the nanowire bundles provides a preferential path for rapid liquid flow, leading to 2 times higher wicking capability of the hollow hierarchical surface comparing with the conventional hierarchical surface. The unique mechanism of preferential capillary pumping revealed in this work paves the way for wicking enhancement and provides an insight into the design of wicking surfaces for high-performance capillary evaporation in a broad range of applications.
许多研究都集中在设计微/纳米结构表面，以提高在许多工业应用中实现快速液体传输的芯吸能力。尽管分级表面已被证明能增强芯吸能力，但液体传输的潜在机制仍不清楚。在此，我们报道了具有内部纳米结构的中空分级表面上的优先毛细泵送现象，这与具有外部纳米结构的传统固体分级表面不同。具体而言，通过共聚焦激光扫描荧光显微镜观察到，在中空分级表面上，毛细泵送优先发生在纳米线束中，而不是相互连接的V形槽中。理论分析表明，毛细泵送能力主要取决于纳米线直径，纳米线束中的毛细爬升速度比微尺度V形槽中的高15.5倍。在纳米线束和V形槽之间的拉普拉斯压差驱动下，优先毛细泵送随着纳米线直径的减小而增强。纳米线束的毛细泵送为快速液体流动提供了一条优先路径，使得中空分级表面的芯吸能力比传统分级表面高2倍。这项工作中揭示的优先毛细泵送的独特机制为增强芯吸能力铺平了道路，并为广泛应用中高性能毛细蒸发的芯吸表面设计提供了思路。
