Peeling from a liquid

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Understanding the behavior of solid sheets interacting with liquid interfaces is crucial in various scientific and engineering fields.
• Previous studies have explored fluid-sheet interactions, but the specific phenomenon of curvature changes at the contact line remains less understood.

Purpose of the Study:

• To establish the existence of a cusp in the curvature of a solid sheet at its contact with a liquid subphase.
• To investigate this phenomenon in two distinct geometric configurations: a straight contact line and a circular contact line.
• To determine if a universal boundary condition governs the sheet's behavior at the contact line across different geometries.

Main Methods:

• Experimental study of floating solid sheets in contact with a liquid subphase.
• Analysis of two configurations: a rectangular sheet lifted at one edge (straight contact line) and a gas bubble injected beneath a floating sheet (circular contact line).
• Mathematical analysis of the sheet's curvature and its derivatives at the solid-vapor-liquid contact line.

Main Results:

• The existence of a cusp in the curvature of the solid sheet at the liquid contact line was established.
• In both studied geometries, the derivative of the sheet's curvature was found to be discontinuous.
• Identical boundary conditions at the contact line were demonstrated for both configurations, despite differences in contact line shape and stress distribution.

Conclusions:

• A cusp in curvature exists at the solid-liquid contact line for floating sheets.
• The boundary condition at the contact line is universal, irrespective of the contact line's geometry or the stress distribution within the sheet.
• This finding provides a fundamental insight into the mechanics of solid-fluid interfaces.