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Spontaneous recovery of superhydrophobicity on nanotextured surfaces.
Proc Natl Acad Sci U S A 2016; 113(20):5508-13PN

Abstract

Rough or textured hydrophobic surfaces are dubbed "superhydrophobic" due to their numerous desirable properties, such as water repellency and interfacial slip. Superhydrophobicity stems from an aversion of water for the hydrophobic surface texture, so that a water droplet in the superhydrophobic "Cassie state" contacts only the tips of the rough surface. However, superhydrophobicity is remarkably fragile and can break down due to the wetting of the surface texture to yield the "Wenzel state" under various conditions, such as elevated pressures or droplet impact. Moreover, due to large energetic barriers that impede the reverse transition (dewetting), this breakdown in superhydrophobicity is widely believed to be irreversible. Using molecular simulations in conjunction with enhanced sampling techniques, here we show that on surfaces with nanoscale texture, water density fluctuations can lead to a reduction in the free energetic barriers to dewetting by circumventing the classical dewetting pathways. In particular, the fluctuation-mediated dewetting pathway involves a number of transitions between distinct dewetted morphologies, with each transition lowering the resistance to dewetting. Importantly, an understanding of the mechanistic pathways to dewetting and their dependence on pressure allows us to augment the surface texture design, so that the barriers to dewetting are eliminated altogether and the Wenzel state becomes unstable at ambient conditions. Such robust surfaces, which defy classical expectations and can spontaneously recover their superhydrophobicity, could have widespread importance, from underwater operation to phase-change heat transfer applications.

Authors+Show Affiliations

Department of Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104.Department of Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104.Department of Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104 amish.patel@seas.upenn.edu.

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

27140619

Citation

Prakash, Suruchi, et al. "Spontaneous Recovery of Superhydrophobicity On Nanotextured Surfaces." Proceedings of the National Academy of Sciences of the United States of America, vol. 113, no. 20, 2016, pp. 5508-13.
Prakash S, Xi E, Patel AJ. Spontaneous recovery of superhydrophobicity on nanotextured surfaces. Proc Natl Acad Sci USA. 2016;113(20):5508-13.
Prakash, S., Xi, E., & Patel, A. J. (2016). Spontaneous recovery of superhydrophobicity on nanotextured surfaces. Proceedings of the National Academy of Sciences of the United States of America, 113(20), pp. 5508-13. doi:10.1073/pnas.1521753113.
Prakash S, Xi E, Patel AJ. Spontaneous Recovery of Superhydrophobicity On Nanotextured Surfaces. Proc Natl Acad Sci USA. 2016 May 17;113(20):5508-13. PubMed PMID: 27140619.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Spontaneous recovery of superhydrophobicity on nanotextured surfaces. AU - Prakash,Suruchi, AU - Xi,Erte, AU - Patel,Amish J, Y1 - 2016/05/02/ PY - 2016/5/4/entrez PY - 2016/5/4/pubmed PY - 2016/5/4/medline KW - Cassie KW - Wenzel KW - barriers KW - dewetting KW - fluctuations SP - 5508 EP - 13 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc. Natl. Acad. Sci. U.S.A. VL - 113 IS - 20 N2 - Rough or textured hydrophobic surfaces are dubbed "superhydrophobic" due to their numerous desirable properties, such as water repellency and interfacial slip. Superhydrophobicity stems from an aversion of water for the hydrophobic surface texture, so that a water droplet in the superhydrophobic "Cassie state" contacts only the tips of the rough surface. However, superhydrophobicity is remarkably fragile and can break down due to the wetting of the surface texture to yield the "Wenzel state" under various conditions, such as elevated pressures or droplet impact. Moreover, due to large energetic barriers that impede the reverse transition (dewetting), this breakdown in superhydrophobicity is widely believed to be irreversible. Using molecular simulations in conjunction with enhanced sampling techniques, here we show that on surfaces with nanoscale texture, water density fluctuations can lead to a reduction in the free energetic barriers to dewetting by circumventing the classical dewetting pathways. In particular, the fluctuation-mediated dewetting pathway involves a number of transitions between distinct dewetted morphologies, with each transition lowering the resistance to dewetting. Importantly, an understanding of the mechanistic pathways to dewetting and their dependence on pressure allows us to augment the surface texture design, so that the barriers to dewetting are eliminated altogether and the Wenzel state becomes unstable at ambient conditions. Such robust surfaces, which defy classical expectations and can spontaneously recover their superhydrophobicity, could have widespread importance, from underwater operation to phase-change heat transfer applications. SN - 1091-6490 UR - https://www.unboundmedicine.com/medline/citation/27140619/Spontaneous_recovery_of_superhydrophobicity_on_nanotextured_surfaces_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=27140619 DB - PRIME DP - Unbound Medicine ER -