Wetting Behavior of Water Droplets on Hydrophobic Microtextures of Comparable Size

Abstract

The wetting behavior of water droplets on periodically structured hydrophobic surfaces was investigated. The effect of structure geometry, roughness, and relative pore fraction on the contact angles was investigated experimentally for droplets of size comparable to the size of the structures. It was found that surface geometry may induce a transition from groove-filling and Wenzel-like behavior to nonfilling of surface grooves and consequential Cassie-Baxter behavior. Numerical calculations of the free energy of these systems suggest that the equilibrium behavior is in line with the experimental observations. The observations may serve as guidelines for the design of surfaces with the desired wetting behavior.

PDMS-SiO2-TiO2-CaO hybrid materials – Cytocompatibility and nanoscale surface features

“…1) the Young contact angle θY was found to be 91.2°. This result is in agreement with the ones reported in the literature [52], considering the amount of PDMS used in the present work in the preparation of the samples and the values of contact angle referred for PDMS itself, 100° < θY < 110° [52,65].…”

“…Jopp et al for PDMS [65]. In the present case, the measured value θm is 150.6°, is well above the values known for PDMS flat surfaces.…”

“…In contrast, no absorption effect was detected in the case of sample K, indicating a non-filling regime [65]. In fact, it was necessary to increase the drop volume from 2 µL to 10 µL in order to have a static situation for taking the measurements.…”

Analysis of approaches to mathematical description of the characteristics of materials with high hydrophobicity

“…Данное математическое выражение хорошо описы-вает смачивание как гидрофильных, так и супергидро-фобных поверхностей [55][56][57].…”

Roughness-gradient–induced spontaneous motion of droplets on hydrophobic surfaces: A lattice Boltzmann study

“…This shortcoming may, however, be neglected as long as the contact area * nasrollah.moradi@rub.de reflects the structure and energetics of the three phase contact line [10]. The suspended state is often separated from the Wenzel state by a finite free energy barrier, which depends both on the droplet size and roughness characteristics [11,12,13]. On a rough hydrophobic substrate, the apparent contact angle of a droplet in the suspended state is typically higher than in the collapsed state [2,14,15].…”