Meniscus shapes on small diameter fibers

Abstract

Factors that control characteristic height and radius of menisci on cylindrical fibers that vertically penetrate a free fluid interface are determined for the small fiber limit, where the radius is much smaller than the fluid capillary constant. Shapes of SiO 2 fiber tips etched under the meniscus of an HF solution are used to demonstrate that in the small fiber limit, meniscus height is independent of capillary constant, and depends on fiber radius and fluid contact angle as h( R,Θ) − Rf(Θ), where f(Θ) is extrapolated from theoretical results of Huh and Scriven. As a result, the contact angle can be determined from the shape of etched tips. While meniscus height is proportional to fiber radius, the characteristic meniscus decay length is much larger, remaining on the order of the capillary constant for all values of fiber radius and contact angle.