Mucins are a family of high-molecular-weight glycoproteins and a major macromolecular constituent in slimy mucus gels that are covering the surface of internal biological tissues. A primary role of mucus gels in biological systems is known to be the protection and lubrication of underlying epithelial cell surfaces. This is intuitively well appreciated by both science community and the public, and yet detailed lubrication properties of mucins and mucus gels have remained largely unexplored to date. Detailed and systematic understanding of the lubrication mechanism of mucus gels is significant from many angles; firstly, lubricity of mucus gels is closely related with fundamental functions of various human organs, such as eye blinking, mastication in oral cavity, swallowing through esophagus, digestion in stomach, breathing through air way and respiratory organs, and thus often indicates the health state of those organs. Furthermore, for the application of various tissue-contacting devices or personal care products, e.g. catheters, endoscopes, and contact lenses, mucus gel layer is the first counter surface that comes into the mechanical and tribological contacts with them. Finally, remarkable lubricating performance by mucins and mucus gels in biological systems may provide many useful and possibly innovative hints in utilizing water as base lubricant for man-made engineering systems. This project thus proposes to carry out a 5 year research program focusing on exploring the lubricity of mucins and mucus gels by combining a broad range of experimental approaches in biology and tribology.