Wetting and wrapping of a floating droplet by a thin elastic filament

TL;DR

This study investigates how a floating elastic filament interacts with a droplet on a fluid surface, revealing geometric and elastic principles governing wetting and wrapping phenomena with experimental and theoretical insights.

Contribution

It introduces a quasi-2D experimental system to analyze droplet-filament wetting, demonstrating the applicability of geometric and elastic theories to describe the system's equilibria.

Findings

Geometric theory accurately predicts contact angles and equilibria.

Elastic Young-Laplace-Dupré relation applies to tension estimates.

Seamless wrapping occurs with high filament bendability.

Abstract

We study the wetting of a thin elastic filament floating on a fluid surface by a droplet of another, immiscible fluid. This quasi-2D experimental system is the lower-dimensional counterpart of the wetting and wrapping of a droplet by an elastic sheet. The simplicity of this system allows us to study the phenomenology of partial wetting and wrapping of the droplet by measuring angles of contact as a function of the elasticity of the filament, the applied tension and the curvature of the droplet. We find that a purely geometric theory gives a good description of the mechanical equilibria in the system. The estimates of applied tension and tension in the filament obey an elastic version of the Young-Laplace-Dupr\'e relation. However, curvatures close to the contact line are not captured by the geometric theory, possibly because of 3D effects at the contact line. We also find that when a highly-bendable filament completely wraps the droplet, there is continuity of curvature at the droplet-filament interface, leading to seamless wrapping as observed in a 3D droplet.