Dynamic hysteresis of an oscillatory contact line

TL;DR

This paper investigates dynamic hysteresis in oscillatory wetting, revealing its dependence on surface molecular layer flexibility and proposing models for accurate contact line motion prediction.

Contribution

It introduces the concept of dynamic hysteresis in oscillatory contact lines and links it to surface layer flexibility, proposing alternative modeling approaches.

Findings

Dynamic hysteresis is tunable via surface molecular layers.

It is not caused by dissipative effects but by surface layer flexibility.

Generalized Hocking's law and GNBC can model dynamic hysteresis effectively.

Abstract

During oscillatory wetting, a phase retardation emerges between contact angle variation and contact line velocity, presenting as a hysteresis loop in their correlation -- an effect we term dynamic hysteresis. This phenomenon is found to be tunable by modifying the surface with different molecular layers. A comparative analysis of dynamic hysteresis, static hysteresis, and contact line friction coefficients across diverse substrates reveals that dynamic hysteresis is not a result of dissipative effects but is instead proportionally linked to the flexibility of the grafted layer on the surface. In the quest for appropriate conditions to model oscillatory contact line motion, we identify the generalized Hocking's linear law and modified Generalized Navier Boundary Condition (GNBC) as alternative options for predicting realistic dynamic hysteresis.