Guo Lin, Kumar Satish, Yang Mingyang, Tang Guihua, Liu Zhigang
Energy Research Institute, Qilu University of Technology, Jinan 250014, P.R. China.
G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Nanoscale. 2022 Jan 6;14(2):525-533. doi: 10.1039/d1nr05906h.
Cactus spines have inspired a wide range of micro- and nano-structures that cause droplets to move spontaneously and directionally. The conical shape and the surface wettability gradient are two typical characteristics in such systems. The cross section of the existing conical fibers is usually assumed to be an ideal circle. In fact, microridges are observed on the spine surface of the cactus, and the function is not yet fully understood. The present work thus focuses on how microridges affect droplet self-transport. Structures mimicking microridges are first investigated by constructing pyramidal cross sections with concave or convex lateral faces. The dissipative particle dynamics method is then employed to numerically investigate and theoretically analyze the dynamic behaviors of droplets on these conical fibers with different cross sections. The results show that the microridges reduce the base radius and the contact area of the droplet, thereby increasing the driving force and reducing the friction force. Moreover, by mimicking the microridges structure, we propose a conical fiber with a triple concave cross section, which increases the droplet velocity and the distance traveled over the traditional circular fiber. This work reveals the role of the microridges in the droplet self-transport, which opens up new prospects for the manufacture of fiber systems for microfluidics and liquid manipulation.
仙人掌刺启发了一系列能使液滴自发且定向移动的微纳结构。圆锥形状和表面润湿性梯度是此类系统的两个典型特征。现有圆锥纤维的横截面通常被假定为理想圆形。实际上，在仙人掌的刺表面观察到了微脊，但其功能尚未完全明了。因此，当前工作聚焦于微脊如何影响液滴的自运输。首先通过构建具有凹面或凸面侧面的金字塔形横截面来研究模仿微脊的结构。然后采用耗散粒子动力学方法对这些具有不同横截面的圆锥纤维上液滴的动态行为进行数值研究和理论分析。结果表明，微脊减小了液滴的基部半径和接触面积，从而增加了驱动力并减小了摩擦力。此外，通过模仿微脊结构，我们提出了一种具有三重凹面横截面的圆锥纤维，它比传统圆形纤维增加了液滴速度和行进距离。这项工作揭示了微脊在液滴自运输中的作用，为制造用于微流体和液体操控的纤维系统开辟了新前景。
