Wong Tak-Sing, Huang Adam Po-Hao, Ho Chih-Ming
Mechanical and Aerospace Engineering Department, University of California, Los Angeles, California 90095, USA.
Langmuir. 2009 Jun 16;25(12):6599-603. doi: 10.1021/la900874f.
Pinning of a liquid contact line by micro/nanoscale defects is attributed as the physical origin of macroscopic contact angle hysteresis. However, direct experimental quantification of the pinning effect at the nanoscale has yet to be fully explored to establish this link. Here we present an experimental technique to systematically investigate the wetting behaviors of individual hydrophilic nanostructures with diameters from 2000 nm down to 75 nm. Our results show that the macroscopic pinning behavior is preserved for nanostructures with dimensions down to approximately 200 nm. In addition, the estimated depinning liquid contact angle at the nanoscale is in agreement with the macroscopic receding contact angle, which indicates a physical link between nanoscopic pinning to the macroscopic liquid receding phenomenon.
微/纳米尺度缺陷对液体接触线的钉扎被认为是宏观接触角滞后的物理起源。然而，纳米尺度钉扎效应的直接实验量化尚未得到充分探索以建立这种联系。在此，我们提出一种实验技术，用于系统地研究直径从2000纳米至75纳米的单个亲水性纳米结构的润湿行为。我们的结果表明，尺寸低至约200纳米的纳米结构仍保留宏观钉扎行为。此外，纳米尺度下估计的脱钉液体接触角与宏观后退接触角一致，这表明纳米钉扎与宏观液体后退现象之间存在物理联系。
