Wetting on smooth micropatterned defects

TL;DR

This paper presents a scale-independent model predicting contact angle hysteresis caused by smooth micropatterned defects, validated by experiments, with potential implications for understanding natural surface defects.

Contribution

The authors develop a novel, scale-independent model for contact angle hysteresis on smooth micropatterned defects, validated through experiments.

Findings

Model accurately predicts contact angle hysteresis.

Hysteresis depends on defect aspect ratio, not size.

Experimental results confirm the model's validity.

Abstract

We develop a model which predicts the contact angle hysteresis introduced by smooth micropatterned defects. The defects are modeled by a smooth function and the contact angle hysteresis is explained using a tangent line solution. When the liquid micro-meniscus touches both sides of the defect simultaneously, depinning of the contact line occurs. The defects are fabricated using a photoresist and experimental results confirm the model. An important point is that the model is scale-independent, i.e. the contact angle hysteresis is dependent on the aspect ratio of the function, not on its absolute size; this could have implications for natural surface defects.