Abstract
The dynamic wetting characteristics of water droplets on silicon wafers with microscale regular pillars structures and fresh lotus leaves are investigated experimentally. We measured the static contact angle, contact angle hysteresis, and roll-off angle of water droplets on both of these superhydrophobic surfaces with a high speed contact angle meter. The dynamic contact angles and internal velocity distribution of water droplets on superhydrophobic surfaces were studied with a high-speed camera system and a particle image velocimetry (PIV) system, respectively. We found that the acceleration of water droplets when they slide off lotus leaves is greater than that of water droplets sliding off the silicon wafers with microscale pillar structures although the static contact angles of water droplets on lotus leaves are slightly smaller than those on the silicon wafers. The reason is that water droplets sliding off lotus leaves have smaller contact angle hysteresis and larger slip velocities. These results indicate that the dynamic contact angle hysteresis and sliding acceleration of liquid droplets are more suitable for reflecting the hydrophobicity of material surfaces compared with static contact angles. Our experiments also show that lotus leaves with multiscale micro/nanostructures have stronger hydrophobicity and self-cleaning properties compared with the micro-structured superhydrophobic surfaces.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Hu D L, Chan B, Bush J W M. The hydrodynamics of water strider locomotion. Nature, 2003, 424: 663–666
Otten A, Herminghaus S. How plants keep dry: A physicist’s point of view. Langmuir, 2004, 20: 2405–2408
Barthlott W, Neinhuis C. Purity of the sacred lotus, or escape from contamination in biological surfaces. Planta, 1997, 202: 1–8
Blossey R. Self-cleaning surfaces-virtual realities. Nat Mater, 2003, 2: 301–306
Parker A, Lawrence C. Water capture by a desert beetle. Nature, 2001, 414: 33–34
Eijkel J. Liquid slip in micro- and nanofluidics: Recent research and its possible implications. Lab Chip, 2007, 7: 299–301
Sanchez C, Arribart H, Guille M M G. Biomimetism and bioinspiration as tools for the design of innovative materials and systems. Nat Mater, 2005, 4: 277–278
Wenzel R N. Resistance of solid surfaces to wetting by water. Ind Eng Chem, 1936, 28: 988–994
Cassie A B D, Baxter S. Wettability of porous surfaces. Trans Faraday Soc, 1944, 40: 546–550
Onda T, Shibuichi S, Satoh N, et al. Super-water-repellent fractal surfaces. Langmuir, 1996, 12: 2125–2127
Wong T, Ho C M. Dependence of macroscopic wetting on nanoscopic surface textures. Langmuir, 2009, 25: 12851–12854
Furmidge C G L. Studies at Phase Interphases 1 Sliding of liquid drops on solid surfaces and a theory for spray for retention. J Colloid Sci, 1962, 17: 309–319
Miwa M, Fujishima A, Nakajima A, et al. Effects of the surface roughness on sliding angles of water droplets on superhydrophobic surfaces. Langmuir, 2000, 16: 5754–5760
Yoshimitsu Z, Nakajima A, Watanabe T, et al. Effects of surface structure on the hydrophobicity and sliding behavior of water droplets. Langmuir, 2002 18: 5818–5822
Nakajima A. Design of a transparent hydrophobic coating. J Ceram Soc Jpn, 2004, 112: 533–540
Yoshida N, Abe Y, Shigeta H, et al. Preparation and water droplet sliding properties of transparent hydrophobic polymer coating by molecular design for self-organization. J Sol Gel Sci Tech, 2004, 31: 195–199
Suzuki S, Nakajima A, Kameshima Y, et al. Elongation and contraction of water droplet during sliding on the silicon surface treated by fluoroalkylsilane. Surf Sci, 2004, 557: L163–L168
Song J H, Sakai M, Yoshida N, et al. Dynamic hydrophobicity of water droplets on the line-patterned hydrophobic surfaces. Surf Sci, 2006, 600: 2711–2717
Yoshida N, Abe Y, Shigeta H, et al. Sliding behavior of water droplets on flat polymer surface. J Am Chem Soc, 2006, 128: 743–747
Lv C J, Yang C Y, Hao P F, et al. Sliding of water droplets on microstructured hydrophobic surfaces. Langmuir, 2010, 26: 8704–8708
Dorrer C, Ruhe J. Advancing and receding motion of droplets on ultrahydrophobic post surfaces. Langmuir, 2006, 22: 7652–7657
Hao P F, Lv C J, Yao Z H, et al. Sliding behavior of water droplet on superhydrophobic surface. Eur Phys Lett, 2010, 90: 66003
Sakai M, Song J H, Yoshida N, et al. Direct observation of internal fluidity in a water droplet during sliding on hydrophobic surfaces. Langmuir, 2006, 22: 4906–4909
Suzuki S, Nakajima A, Sakai M. Rolling and slipping motion of a water droplet sandwiched between two parallel plates coated with fluoroalkylsilanes. Appl Surf Sci, 2008, 255: 3414–3420
Sakai M, Kono H, Nakajima A. Sliding of water droplets on the superhydrophobic surface with ZnO nanorods. Langmuir, 2009, 25: 14182–14186
Bhushan B, Koch K, Jung Y C. Fabrication and characterization of the hierarchical structure for superhydrophobicity and self-cleaning. Ultramicroscopy, 2009, 109:1029–1034
Koch K, Bhushan B, Jung Y C, et al. Fabrication of artificial Lotus leaves and significance of hierarchical structure for superhydrophobicity and low adhesion. Soft Matter, 2009, 5: 1386–1393
Jung Y C, Bhushan B. Biomimetic structures for fluid drag reduction in laminar and turbulent flows. J Phys Condens Matter, 2010, 22: 035104
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hao, P., Yao, Z. & Zhang, X. Study of dynamic hydrophobicity of micro-structured hydrophobic surfaces and lotus leaves. Sci. China Phys. Mech. Astron. 54, 675–682 (2011). https://doi.org/10.1007/s11433-011-4269-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11433-011-4269-1