Apparent Contact Angle of Droplets on Liquid Infused Surfaces: Geometric Interpretation

TL;DR

This paper provides a geometric interpretation and simplified formulas for the apparent contact angle of droplets on liquid infused surfaces, considering the size of the wetting ridge and pressure differences.

Contribution

It introduces a new geometric perspective and compact analytical expressions for the apparent contact angle, improving upon previous models.

Findings

Variation in contact angle explained by Neumann triangle rotation

Derived linear and quadratic correction formulas

Simpler expressions compared to prior work

Abstract

We theoretically investigate the apparent contact angle of droplets on liquid infused surfaces as a function of the relative size of the wetting ridge and the deposited droplet. We provide an intuitive geometrical interpretation whereby the variation in the apparent contact angle is due to the rotation of the Neumann triangle. We also derive linear and quadratic corrections to the apparent contact angle as power series expansion in terms of pressure differences between the lubricant, droplet and gas phases. These expressions are much simpler and more compact compared to those previously derived by Semprebon et al. [Soft Matter, 2017, 13, 101-110].