Wetting of soap bubbles on hydrophilic, hydrophobic and superhydrophobic surfaces

TL;DR

This study investigates how soap bubbles wet different surfaces, presenting a model for contact angles that aligns with experimental data, revealing how surface properties influence bubble behavior and contact angles.

Contribution

A new model for the contact angle of sessile bubbles on various surfaces, validated by experiments, highlighting the role of Plateau borders and surface wettability.

Findings

Contact angle is 90° on hydrophilic surfaces and 134° on superhydrophobic surfaces.

Bubble contact angle decreases with radius on hydrophilic surfaces.

Bubble contact angle increases with radius on superhydrophobic surfaces.

Abstract

Wetting of sessile bubbles on solid and liquid surfaces has been studied. A model is presented for the contact angle of a sessile bubble based on a modified Young equation - the experimental results agree with the model. A hydrophilic surface results in a bubble contact angle of 90 deg whereas on a superhydrophobic surface one observes 134 deg. For hydrophilic surfaces, the bubble angle diminishes with bubble radius - whereas on a superhydrophobic surface, the bubble angle increases. The size of the Plateau borders governs the bubble contact angle - depending on the wetting of the surface.