Three-phase contact line and line tension of electrolyte solutions in contact with charged substrates

TL;DR

This study uses classical density functional theory to analyze how substrate charge density and ionic strength affect the structure and line tension of the three-phase contact line in electrolyte solutions, revealing a consistently negative line tension.

Contribution

It provides a detailed theoretical analysis of the influence of substrate charge and ionic strength on the contact line and line tension in electrolyte solutions, a topic with limited prior quantitative understanding.

Findings

Line tension is negative across all conditions studied.

Line tension magnitude decreases with decreasing contact angle.

Substrate charge density and ionic strength significantly influence contact line structure.

Abstract

The three-phase contact line formed by the intersection of a liquid-vapor interface of an electrolyte solution with a charged planar substrate is studied in terms of classical density functional theory applied to a lattice model. The influence of the substrate charge density and of the ionic strength of the solution on the intrinsic structure of the three-phase contact line and on the corresponding line tension is analyzed. We find a negative line tension for all values of the surface charge density and of the ionic strength considered. The strength of the line tension decreases upon decreasing the contact angle via varying either the temperature or the substrate charge density.