title: Multiscale treatment of theoretical mechanisms for the protection of hydrogel surfaces from adhesive forces.
abstract: One role of a lubricant is to prevent wear of two surfaces in contact, which is likely to be the result of adhesive forces that cause a pair of asperities belonging to two surfaces in contact to stick together. Such adhesive sticking of asperities can occur both for sliding surfaces and for surfaces which are pressed together and then pulled apart. The latter situation, for example, is important for contact lenses, as prevention of sticking reduces possible damage to the cornea as the lenses are inserted and removed from the eye. Contact lenses are made from both neutral and polyelectrolyte hydrogels. It is demonstrated here that sticking of neutral hydrogels can be prevented by repulsive forces between asperities in contact, resulting from polymers attached to the gel surface but not linked with each other. For polyelectrolyte hydrogels, it is shown that osmotic pressure due to counterions, held at the interface between asperities in contact by the electrostatic attraction between the ions and the fixed charges in the gel, can provide a sufficiently strong repulsive force to prevent adhesive sticking of small-length-scale asperities.
authors.affiliation: Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Sokoloff
mesh_terms: D000268:Adhesiveness; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D008962:Models, Theoretical; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties
chemical_list: D011108:Polymers; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate