5 - Thermodynamics of contact angles on rough, heterogeneous surfaces

Abstract

Publisher Summary This chapter presents a comprehensive study on the thermodynamics of contact angles on general rough, heterogeneous surfaces. Conventionally, contact is defined as the angle formed between a liquid-vapor interface and a liquid-solid interface at the solid-liquid-vapor three-phase contact line. On an ideal solid surface, which is smooth, homogeneous, isotropic, and non-deformable, the contact angle is expressed by the Young equation. The concept of liquid front simplified the thermodynamic treatments of contact angles on rough, heterogeneous surfaces and thus made it possible to model real surfaces. Receding contact angles are poorly reproducible for hydrophilic surfaces but for extremely hydrophobic surfaces, advancing contact angles might have a poor reproducibility. An impurity might cause poor reproducibility for receding contact angles if it is the component with the smallest intrinsic contact angle, but it can make the advancing contact angle. An impurity might not affect contact angle hysteresis if it is the component with an intermediate intrinsic contact angle.