Zhang Jilin, Han Yanchun
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate University of the Chinese Academy of Sciences, Changchun 130022, P. R. China.
Langmuir. 2007 May 22;23(11):6136-41. doi: 10.1021/la063376k. Epub 2007 Apr 20.
The approach of water droplets self-running horizontally and uphill without any other forces was proposed by patterning the shape-gradient hydrophilic material (i.e., mica) to the hydrophobic matrix (i.e., wax or low-density polyethylene (LDPE)). The shape-gradient composite surface is the best one to drive water droplet self-running both at the high velocity and the maximal distance among four different geometrical mica/wax composite surfaces. The driving force for the water droplets self-running includes: (1) the great difference in wettability of surface materials, (2) the low contact angle hysteresis of surface materials, and (3) the space limitation of the shape-gradient transportation area. Furthermore, the average velocity and the maximal distance of the self-running were mainly determined by the gradient angle (alpha), the droplet volume, and the difference of the contact angle hysteresis. Theoretical analysis is in agreement with the experimental results.
通过将形状梯度亲水性材料（即云母）图案化到疏水性基质（即蜡或低密度聚乙烯（LDPE））上，提出了水滴在没有任何其他外力的情况下水平且向上自行流动的方法。在四种不同几何形状的云母/蜡复合表面中，形状梯度复合表面是驱动水滴以最高速度和最大距离自行流动的最佳表面。水滴自行流动的驱动力包括：（1）表面材料润湿性的巨大差异，（2）表面材料的低接触角滞后，以及（3）形状梯度传输区域的空间限制。此外，自行流动的平均速度和最大距离主要由梯度角（α）、液滴体积和接触角滞后的差异决定。理论分析与实验结果一致。
