Exploring the Lotus Effect
The superhydrophobic properties of the lotus leaf have been synthetically reproduced as a fabric treatment used for water- and stain-repellent clothing and other applications. A water droplet on these surfaces "floats" on a cushion of air and easily rolls off the material.Copyright (left) Michael Gasperl, Wikimedia Commons and (right) 2010 Jean Stave http://commons.wikimedia.org/wiki/File:Tropaeolum-majus%28Lotus-oben%29.jpg
Students test and observe the "self-cleaning" lotus effect using a lotus leaf and cloth treated with a synthetic lotus-like superhydrophobic coating. They also observe the Wenzel and Cassie Baxter wetting states by creating and manipulating condensation droplets on the leaf surface. They consider the real-life engineering applications for these amazing water-repellent and self-cleaning properties.
Inspired by the lotus leaf, a revolution in self-cleaning surfaces is underway. Many researchers and engineers are developing synthetic superhydrophobic materials and products that mimic the lotus leaf's extremely water-repellent and self-cleaning properties. These materials and textiles would enable skyscraper windows and walls to never need human cleaning, not to mention an unlimited number of other objects: tents and awnings, painted houses, vehicle undercarriages, etc. Already in everyday use is clothing fabric that repels ketchup, mustard, red wine and coffee. Extreme water-shedding materials have the potential for applications in energy and medicine. Some technologists are developing self-deodorizing and disinfectant surfaces for bathrooms and hospitals, as well as similar technologies for keeping surfaces from fogging. Some technologies use the "lotus effect," whereas others employ the opposite property — superhydrophilicity. Future products may combine the two properties or use substances that can be switched back and forth to control the flow of liquids through microfluidic components.
After this activity, students should be able to:
- Describe the behavior of water on superhydrophobic surfaces.
- Define "lotus effect" and describe its water-repellent and self-cleaning properties.
- Explore how damage to Nano-TexTM cloth affects its "lotus effect" properties.