Wetting morphologies on an array of fibers of different radii

TL;DR

This study analyzes how liquid morphologies on two parallel fibers of different radii depend on fiber size and spacing, providing an analytical model validated by experiments, relevant for understanding capillary behavior in fiber arrays.

Contribution

The paper introduces an analytical prediction for the critical inter-fiber distance for morphology transition on polydisperse fibers, validated by experiments.

Findings

Critical inter-fiber distance depends on fiber radii and contact angle.

Experimental results agree with the analytical model.

Polydispersity influences liquid morphology and transition points.

Abstract

We investigate the equilibrium morphology of a finite volume of liquid placed on two parallel rigid fibers of different radii. As observed for identical radii fibers, the liquid is either in a column morphology or adopts a drop shape depending on the inter-fiber distance. However the cross-sectional area and the critical inter-fiber distance at which the transition occurs are both modified by the polydispersity of the fibers. Using energy considerations, we analytically predict the critical inter-fiber distance corresponding to the transition between the column and the drop morphologies occurs. This distance depends both on the radii of the fibers and on the contact angle of the liquid. We perform experiments using a perfectly wetting liquid on two parallel nylon fibers: the results are in good agreement with our analytical model. The morphology of the capillary bridges between fibers of different radii is relevant to the modeling of large arrays of polydisperse fibers.