title: Contact angle patterns on low-energy surfaces.
abstract: It is well-known that on a given low-energy solid surface, the contact angles of different organic liquids follow a regular pattern. The experimental evidence for this, and semi-empirical equations describing the pattern, are reviewed. Theoretical and computational efforts to explain the pattern are discussed, and a simplified analytical approach is presented. The main pattern of contact angles is seen to arise from two factors: a common combining rule for liquid-solid molecular interactions, and the reduced density of liquid molecules adjacent to a lower-energy solid surface. Irregular departures from the main pattern are due to chemical effects originating in molecular structure.
authors.affiliation: Department of Mechanical & Industrial Engineering, University of Toronto, 5 King's College Rd., room RM501, Toronto, ON, Canada, M5S 3G8. Electronic address: robertd@mie.utoronto.ca.
authors.forename: Robert
authors.initials: R
authors.lastname: David
authors.affiliation: Department of Mechanical & Industrial Engineering, University of Toronto, 5 King's College Rd., room RM501, Toronto, ON, Canada, M5S 3G8.
authors.forename: A Wilhelm
authors.initials: AW
authors.lastname: Neumann
keywords: Zisman plot; contact angle; density depletion; equation of state for interfacial tensions; low-energy surface