This closely related lesson, also from TryEngineering, explores the hydrophobic effect in roofing materials. Both are appropriate for the secondary grades.

This article describes how scientists have borrowed from one of nature's most water repellant surfaces (the lotus leaf) to develop inexpensive synthetic coatings.

This article by Kerstin Koch, Rhine-Waal University of Applied Science, describes how surface sculptures play a key role in water repellancy. Provides an excellent explanation of how the lotus leaf surface structure acts to reduce adhesion of liquids (includes SEM image of the cellular structure).