Hydrophobic literally means “water-avoiding” but is generally used for water-repellent. A surface is called hydrophob if it has a lower surface tension than water (72 mN/m) or if the contact angle is more than 90° to water. This means that the water does not melt on the surface, but contracts spherically.
Well-known examples include Teflon pans coated with PTFE or the naturally occurring lotus leaves that coined the term “lotus effect”. The opposite of hydrophobic is hydrophilic. The surface energy can be transferred from hydrophobicity to hydrophilicity by plasma treatment.« Back to Glossary Index