Size-dependent contact angle, and wetting and drying transition of a droplet adsorbed on to a spherical substrate: Line tension effect

Abstract

The size-dependent contact angle and the drying and wetting morphological transition are studied with respect to the volume change for a spherical cap-shaped droplet placed on a spherical substrate. The line-tension effect is included using the rigorous formula for the Helmholtz free energy in the droplet capillary model. A morphological drying transition from a cap-shaped to a spherical droplet occurs when the substrate is hydrophobic and the droplet volume is small, similar to the transition predicted on a flat substrate. In addition, a morphological wetting transition from a cap-shaped to a wrapped spherical droplet occurs for a hydrophilic substrate and a large droplet volume. The contact angle depends on the droplet size: it decreases as the droplet volume increases when the line tension is positive, whereas it increases when the line tension is negative. The spherical droplets and wrapped droplets are stable when the line tension is positive and large.

10 pages 11 figures, to be published in Physical Review E

References in corpus (3)

• Conceptual aspects of line tensions
• Contact line stability of ridges and drops
• Line tension and wettability of nanodrops on curved surfaces

Cited by in corpus (3)

• Spreading law of non-Newtonian power-law liquids on a spherical substrate by energy balance approach
• Four stages of droplet spreading on a spherical substrate and in a spherical cavity -Surface tension vs line tension and viscous dissipation vs frictional dissipation-
• Topography- and topology-driven spreading of non-Newtonian power-law liquids on a flat and a spherical substrate