title: Friction studies of hydrogel contact lenses using AFM: non-crosslinked polymers of low friction at the surface.
abstract: The surface of soft contact lenses made of crosslinked poly(2-hydroxyethyl methacrylate). pHEMA, has been investigated with atomic force microscopy in contact mode. The friction force and adhesive force measurements were able to differentiate the non-crosslinked pHEMA chains from the surface of the crosslinked pHEMA networks. These non-crosslinked pHEMA chains at the surface were anchored to the crosslinked pHEMA network, most likely by entanglement and their surfaces were about 2-4nm higher than the surrounding surface in a dehydrated state. In saline solution, the surface friction and adhesive force of the contact lens were significantly reduced compared to those measured for the surface-dehydrated contact lens.
authors.affiliation: Department of Chemistry University of California at Berkeley, 94720, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: C
authors.initials: C
authors.lastname: Marmo
authors.forename: G A
authors.initials: GA
authors.lastname: Somorjai
mesh_terms: D000268:Adhesiveness; D001672:Biocompatible Materials / Q000737:chemistry*; D003263:Contact Lenses, Hydrophilic; D003890:Desiccation; D017276:Friction; D020100:Hydrogels / Q000737:chemistry*; D008422:Materials Testing; D000432:Methanol; D018625:Microscopy, Atomic Force; D011102:Polyhydroxyethyl Methacrylate / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012965:Sodium Chloride; D013499:Surface Properties; D014867:Water
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D011108:Polymers; D014867:Water; D011102:Polyhydroxyethyl Methacrylate; D012965:Sodium Chloride; D000432:Methanol