Simple method for measuring intrinsic contact angle of a fiber with liquids

A simple method is developed to directly measure the intrinsic contact angle of a fiber (i.e., Young–Laplace contact angle of the fiber material) with any arbitrary liquid. It is shown that the intrinsic contact angle of a fiber can be obtained by simply measuring the angle between the tangent to the fiber surface and the tangent to the droplet at the contact line, if the droplet has a clamshell conformation and is viewed from the longitudinal direction. The novelty of the proposed method is that its predictions are not affected by the volume of the droplet used for the experiment, the wettability of the fiber, the surface tension of the liquid, or the magnitude of the body force acting on the droplet during the experiment. The accuracy of the proposed method is assessed through comparison with computational results obtained from validated numerical simulations or alternative experimental methods.