Abstract:
Dynamic wettability and contact angle hysteresis can be correlated to shed insight onto any solidliquid interaction. Complex fluids are capable of altering the expected hysteresis and dynamic wetting
behavior due to interfacial interactions. We report the effect of capillary number on the dynamic
advancing and receding contact angles of surfactant-based nanocolloidal solutions on hydrophilic,
near hydrophobic, and superhydrophobic surfaces by performing forced wetting and de-wetting
experiments by employing the embedded needle method. A segregated study is performed to infer
the contributing effects of the constituents and effects of particle morphology. The static contact
angle hysteresis is found to be a function of particle and surfactant concentrations and greatly
depends on the nature of the morphology of the particles. An order of estimate of line energy and
a dynamic flow parameter called spreading factor and the transient variations of these parameters
are explored which sheds light on the dynamics of contact line movement and response to perturbation of three-phase contact. The Cox-Voinov-Tanner law was found to hold for hydrophilic and
a weak dependency on superhydrophobic surfaces with capillary number, and even for the complex fluids, with a varying degree of dependency for different fluids. Published by AIP Publishing.
