title: Indirect methods to measure wetting and contact angles on spherical convex and concave surfaces.
abstract: In this work, a method was developed for indirectly estimating contact angles of sessile liquid drops on convex and concave surfaces. Assuming that drops were sufficiently small that no gravitational distortion occurred, equations were derived to compute intrinsic contact angles from the radius of curvature of the solid surface, the volume of the liquid drop, and its contact diameter. These expressions were tested against experimental data for various liquids on polytetrafluoroethylene (PTFE) and polycarbonate (PC) in the form of flat surfaces, spheres, and concave cavities. Intrinsic contact angles estimated indirectly using dimensions and volumes generally agreed with the values measured directly from flat surfaces using the traditional tangent method.
authors.affiliation: Entegris, Inc., 101 Peavey Road, Chaska, Minnesota 55318, USA. chuck_extrand@entegris.com
authors.forename: C W
authors.initials: CW
authors.lastname: Extrand
authors.forename: Sung In
authors.initials: SI
authors.lastname: Moon