Explained: Hydrophobic and Hydrophilic

Sometimes water spreads evenly when it hits a surface; sometimes it beads into tiny droplets. While people have noticed these differences since ancient times, a better understanding of these properties, and new ways of controlling them, may bring important new applications.

Materials with a special affinity for water — those it spreads across, maximizing contact — are known as hydrophilic. Those that naturally repel water, causing droplets to form, are known as hydrophobic. Both classes of materials can have a significant impact on the performance of power plants, electronics, airplane wings and desalination plants, among other technologies, says Kripa Varanasi, an associate professor of mechanical engineering at MIT. Improvements in hydrophilic and hydrophobic surfaces could provide ketchup bottles where the condiment just glides right out, glasses that never fog up, or power plants that wring more electricity from a given amount of fuel. Read more about the critical details and potential uses of hydrophobic materials.