Students learn how plants create and use superhydrophobic surfaces in nature and how engineers have created human-made products that mimic these properties.

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In this lesson and related activity, students learn how plants create and use superhydrophobic surfaces in nature and how engineers have created human-made products that mimic the properties of these natural surfaces.

Summary provided by authors:

“Students are introduced to superhydrophobic surfaces and the “lotus effect.” Water spilled on a superhydrophobic surface does not wet the surface, but simply rolls off. Additionally, as water moves across the superhydrophobic surface, it picks up and carries away any foreign material, such as dust or dirt. Students learn how plants create and use superhydrophobic surfaces in nature and how engineers have created human-made products that mimic the properties of these natural surfaces. They also learn about the tendency of all superhydrophobic surfaces to develop water droplets that do not roll off the surface but become “pinned” under certain conditions, such as water droplets formed from condensation. They see how the introduction of mechanical energy can “unpin” these water droplets and restore the desirable properties of the superhydrophobic surface.”

© 2013 by Regents of the University of Colorado; original © 2011 Duke University.

Created by the NSF CAREER Award and RET Program, Mechanical Engineering and Material Science, Pratt School of Engineering, Duke University.  Contributors: Jean Stave, Durham Public Schools, NC; Chuan-Hua Chen, Mechanical Engineering and Material Science, Pratt School of Engineering, Duke University.

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Objectives

  • Describe situations in which a superhydrophobic lotus-effect surface would be useful.

  • Explain the difference between Cassie-Baxter and Wenzel wetting and how it applies to superhydrophobic surfaces.

  • Demonstrate the transition between Wenzel and Cassie-Baxter wetting states.

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