title: Hydration lubrication: exploring a new paradigm.
abstract: Lubrication by hydration shells that surround, and are firmly attached to, charges in water, and yet are highly fluid, provide a new mode for the extreme reduction of friction in aqueous media. We report new measurements, using a mica surface-force balance, on several different systems which exhibit hydration lubrication, extending earlier studies significantly to shed new light on the nature and limits of this mechanism. These include lubrication by hydrated ions trapped between charged surfaces, and boundary lubrication by surfactants, by polyzwitterionic brushes and by close-packed layers of phosphatidylcholine vesicles. Sliding friction coefficients as low as 10(-4) or even lower, and mean contact pressures of up to 17 MPa or higher are indicated. This suggests that the hydration lubrication mechanism may underlie low-friction sliding in biological systems, in which such pressures are rarely exceeded.
authors.affiliation: Weizmann Institute of Science, Rehovrot, 76100, Israel.
authors.forename: Anastasya
authors.initials: A
authors.lastname: Gaisinskaya
authors.forename: Liran
authors.initials: L
authors.lastname: Ma
authors.forename: Gilad
authors.initials: G
authors.lastname: Silbert
authors.forename: Raya
authors.initials: R
authors.lastname: Sorkin
authors.forename: Odeya
authors.initials: O
authors.lastname: Tairy
authors.forename: Ronit
authors.initials: R
authors.lastname: Goldberg
authors.forename: Nir
authors.initials: N
authors.lastname: Kampf
authors.forename: Jacob
authors.initials: J
authors.lastname: Klein