Wetting refers to the study of how a liquid deposited on a solid surface spreads out.  The phenomenon is relevant to numerous industrial areas and plays an important role in nature.  Join Dr. Daeyeon Lee for a discussion of the fundamental aspects of wetting. Dr. Lee will introduce the concept of contact angle (the angle at which the liquid-vapor interface (boundary) meets the solid surface), hydrophillic surfaces and surfaces that show extreme hydrophobicity in nature. Dr. Lee will show examples of how superhydrophobic and superhydrophilic surfaces could be useful and will show samples of glass slides treated with superhydrophilic coatings and fabrics with superhydrophobic coatings.  He will then apply these concepts to nature, illustrating how beetles living in the Namibian deserts (one of the most arid regions in the world!) can gather water from morning fog. Artificial structures mimicking the backs of Namib desert beetles have been made and these can be used to gather water in dry regions of the world.

About Dr. Daeyeon Lee

Dr. Daeyeon Lee is an Assistant Professor of Chemical and Biomolecular Engineering at the University of Pennsylvania. He received is  B.S. in Chemical Engineering from Seoul National University in 2001 and his Ph.D. in Chemical Engineering from MIT in 2007. The goal of his research group is to extend the basic understanding of soft matter such as colloids, polymers, and nanomaterials to fabricate functional structures with properties designed for advanced applications. The techniques used in the group include layer-by-layer assembly, microfluidics, optical microscopy, electron microscopy, scanning force microscopy, and dissipative quartz crystal microbalance. Using these techniques, the group studies the interactions of various materials at gas-liquid, liquid-liquid and liquid-solid interfaces. Intermolecular and capillary forces between materials are used to generate functional thin films and microcapsules for applications in renewable energy, sustained release, and encapsulation.

Pre-Videoconference Activities

• Familiarize Students with the Article "Self-Cleaning Materials": The article is available under "Resources." The article reports on the development of extremely water-repellent textured surfaces inspired by the microscopic structure of the lotus flower, and other surfaces which have the opposite property, known as superhydrophilicity. The possibility of engineering products which combine the two features, in order to control the microscopic flow of fluids, is discussed.
• Generate Questions for Dr. Lee: Students should develop questions for Dr. Lee regarding the topics covered in the article or questions that arise during the videoconference presentations. We suggest that you come up with a list of questions prior to the videoconference, but also pass out note cards for students to jot down questions during the presentation. We will call on schools in round-robin fashion during the videoconference event.