Lee Jonggyu, Suh Youngjoon, Dubey Pranav P, Barako Michael T, Won Yoonjin
Department of Mechanical and Aerospace Engineering , University of California, Irvine , Irvine , California 92697 , United States.
NG Next, Northrop Grumman Corporation , Redondo Beach , California 90278 , United States.
ACS Appl Mater Interfaces. 2019 Jan 9;11(1):1546-1554. doi: 10.1021/acsami.8b14955. Epub 2018 Dec 28.
Capillary wicking through homogeneous porous media remains challenging to simultaneously optimize due to the unique transport phenomena that occur at different length scales. This challenge may be overcome by introducing hierarchical porous media, which combine tailored morphologies across multiple length scales to design for the individual transport mechanisms. Here, we fabricate hierarchical nanowire arrays consisting of vertically aligned copper nanowires (∼100 to 1000 nm length scale) decorated with dense copper oxide nanostructures (∼10 to 100 nm length scale) to create unique property sets that include a large specific surface area, high rates of fluid delivery, and the structural flexibility of vertical arrays. These hierarchical nanowire arrays possess enhanced capillary wicking ( K/ R = 0.004-0.023 μm) by utilizing hemispreading and are advantageous as evaporation surfaces. With the advent and acceleration of flexible electronics technologies, we measure the capillary properties of our freestanding hierarchical nanowire arrays installed on curved surfaces and observe comparable fluid delivery to flat arrays, showing the difference of 10-20%. The degree of effective inter-nanowire pore and porosity is shown to govern the capillary performance parameters, thereby this study provides the design strategy for capillary wicking materials with unique and tailored combinations of thermofluidic properties.
由于在不同长度尺度上会出现独特的传输现象，通过均匀多孔介质的毛细管芯吸作用难以同时实现优化。引入分级多孔介质可以克服这一挑战，这种介质结合了多个长度尺度上的定制形态，以针对不同的传输机制进行设计。在此，我们制造了分级纳米线阵列，该阵列由垂直排列的铜纳米线（长度尺度约为100至1000纳米）组成，并装饰有致密的氧化铜纳米结构（长度尺度约为10至100纳米），以创造出具有大比表面积、高流体输送速率和垂直阵列结构灵活性等独特性能组合。这些分级纳米线阵列通过利用半球形铺展具有增强的毛细管芯吸作用（K/R = 0.004 - 0.023μm），并且作为蒸发表面具有优势。随着柔性电子技术的出现和加速发展，我们测量了安装在曲面上的独立分级纳米线阵列的毛细管性能，并观察到其流体输送与平面阵列相当，差异为10 - 20%。有效纳米线间孔隙度和孔隙率的程度显示出对毛细管性能参数的控制作用，因此本研究为具有独特和定制热流体性能组合的毛细管芯吸材料提供了设计策略。
