Requirements of Super-Hydrophobic Surface - PowerPoint PPT Presentation

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Requirements of Super-Hydrophobic Surface

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  1. Requirements of Super-Hydrophobic Surface Super hydrophobic surfaces with a water contact angle (CA) greater than 150o

  2. _ Hysteresis H = Requirements of Super-Hydrophobic Surface Super hydrophobic surfaces with a low hysteresis receding contact angle advancing contact angle Small Hysteresis The contact angle hysteresis can be regarded as the force required to move a liquid droplet across a surface. Liquid droplet can roll off easily

  3. Super-Hydrophobic Surfacefrom Nature Lotus Effect Self-Cleaning Adv. Mater. 2002, 14, 1857

  4. Water-Repellent Legs of Water Striders 20 μm 200 nm SEM images of a leg showing numerous oriented spindly microseta and nanoscale grooved structures on a seta L. Jiang Nature2004, 432, 36

  5. Artificial Super-Hydrophobic Surface Super Hydrophobic Surface of Aligned Polyacrylonitrile Nanofibers Transformation of a Simple Plastic into a Superhydrophobic Surface 30℃ 60℃ Science 2003, 299, 1377 Angew. Chem. Int. Ed. 2002, 41, 1221

  6. Two Models of Hydrophobicity (1) R. N. Wenzel, 1936 Θw:CA on the rough surface Θ :CA on the smooth surface r:roughness factor (r >1) cosΘw= rcosΘ D. Quéré Soft Matter 2005, 1, 55

  7. Two Models of Hydrophobicity (2) A. B. D. Cassie, 1948 ΘC:CA on the rough surface Θ:CA on the smooth surface f1:fraction of solid f2:fraction of air (f1+f2 = 1) cosΘc= f1cosΘ–f2 D. Quéré Soft Matter 2005, 1, 55

  8. Conventionally, super-hydrophobic surfaces have been produced mainly in two ways: Create a rough surface (e.g., with a fractal structure) Modify the surface with materials of low surface free energy, such as fluorinated or silicon compounds.