Wetting on Fractal Superhydrophobic Surfaces from “Core−Shell” Particles: A Comparison of Theory and Experiment Export

@article{citeulike:5217338, abstract = {We report an experimental and theoretical investigation of the wetting behavior of different model polar and nonpolar liquids and their mixtures on superhydrophobic fractal surfaces made of polymer- or silane-coated ” core−shell” particles. We compared the experimental results with the theoretical predictions made according to the theories of Onda−Shibuichi (describes wetting on fractal surfaces) and Cassie−Baxter (describes wetting on generic rough composite surfaces). We found that the experimental findings deviate from the behavior predicted by the Onda−Shibuichi model. On the other hand, the wetting properties were found to be close to the predictions made by the Cassie−Baxter model in the hydrophobic region (the intrinsic contact angle on the flat surface is larger than 90°). However, the wetting behavior in the hydrophilic region (the intrinsic contact angle is less than 90°) could not be described by the Onda−Shibuichi or Cassie−Baxter model. The observed inconsistency between the experimental results and theoretical predictions was explained by the formation of metastable states of a liquid droplet on a fabricated fractal surface according to the theory developed by Johnson and Dettre for generic rough surfaces. The entrapments of the liquid droplets in metastable states resulted in superhydrophobic behavior on fractal surfaces as well, made from nonfluorinated material such as polystyrene with a surface free energy of about 30 mJ/m2. This finding is very promising for real industrial applications where fluorinated compounds are willing to be reduced. It can be concluded that employing a texture with fractal geometry is necessary for the design of superhydrophobic coatings. Thereby, extremely lowering the surface free energy of materials by fluorination is not an obligatory factor for the generation of liquid-repellent superhydrophobic materials. We believe that the results we presented in the paper give new insight into the understanding of wetting not only on general superhydrophobic rough surfaces but also on fractal surfaces.}, author = {Synytska, Alla and Ionov, Leonid and Grundke, Karina and Stamm, Manfred}, citeulike-article-id = {5217338}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/la803120d}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/la803120d}, day = {3}, doi = {10.1021/la803120d}, journal = {Langmuir}, keywords = {cassie, dual-scale-roughness, fractal, wenzel, wetting-theory}, month = {March}, number = {5}, pages = {3132--3136}, posted-at = {2009-07-21 10:26:03}, priority = {2}, title = {Wetting on Fractal Superhydrophobic Surfaces from ” Core−Shell” Particles: A Comparison of Theory and Experiment}, url = {http://dx.doi.org/10.1021/la803120d}, volume = {25}, year = {2009} }

TY - JOUR ID - citeulike:5217338 L3 - citeulike-article-id:5217338 N2 - We report an experimental and theoretical investigation of the wetting behavior of different model polar and nonpolar liquids and their mixtures on superhydrophobic fractal surfaces made of polymer- or silane-coated “core−shell” particles. We compared the experimental results with the theoretical predictions made according to the theories of Onda−Shibuichi (describes wetting on fractal surfaces) and Cassie−Baxter (describes wetting on generic rough composite surfaces). We found that the experimental findings deviate from the behavior predicted by the Onda−Shibuichi model. On the other hand, the wetting properties were found to be close to the predictions made by the Cassie−Baxter model in the hydrophobic region (the intrinsic contact angle on the flat surface is larger than 90°). However, the wetting behavior in the hydrophilic region (the intrinsic contact angle is less than 90°) could not be described by the Onda−Shibuichi or Cassie−Baxter model. The observed inconsistency between the experimental results and theoretical predictions was explained by the formation of metastable states of a liquid droplet on a fabricated fractal surface according to the theory developed by Johnson and Dettre for generic rough surfaces. The entrapments of the liquid droplets in metastable states resulted in superhydrophobic behavior on fractal surfaces as well, made from nonfluorinated material such as polystyrene with a surface free energy of about 30 mJ/m2. This finding is very promising for real industrial applications where fluorinated compounds are willing to be reduced. It can be concluded that employing a texture with fractal geometry is necessary for the design of superhydrophobic coatings. Thereby, extremely lowering the surface free energy of materials by fluorination is not an obligatory factor for the generation of liquid-repellent superhydrophobic materials. We believe that the results we presented in the paper give new insight into the understanding of wetting not only on general superhydrophobic rough surfaces but also on fractal surfaces. IS - 5 JF - Langmuir EP - 3136 TI - Wetting on Fractal Superhydrophobic Surfaces from “Core−Shell” Particles: A Comparison of Theory and Experiment VL - 25 SP - 3132 KW - cassie KW - dual-scale-roughness KW - fractal KW - wenzel KW - wetting-theory AU - Synytska, Alla AU - Ionov, Leonid AU - Grundke, Karina AU - Stamm, Manfred PY - 2009/03/03/ UR - http://dx.doi.org/10.1021/la803120d ER -