Droplet evaporation on porous fabric materials.

Droplet evaporation on porous materials is a complex dynamic that occurs with spontaneous liquid imbibition through pores by capillary action. Here, we explore water dynamics on a porous fabric substrate with in-situ observations of X-ray and optical imaging techniques. We show how spreading and wicking lead to water imbibition through a porous substrate, enhancing the wetted surface area and consequently promoting evaporation.

Evaporation and deposition of inclined colloidal droplets.

Colloidal droplets on flat solid substrates commonly leave symmetric ring-like deposits due to coffee-ring flows during evaporation. On inclined substrates, droplet shapes may become asymmetric by gravity. On this basis, it is not clear how their evaporation dynamics and final deposits are changed depending on inclination.

Evaporation-induced alignment of nanorods in a thin film.

During the solvent evaporation of a thin film, Brownian rod-shaped particles self-assemble into microstructures and their orientation arrangements change while their volume fractions increase. We have studied the phenomena using a simple model which accounts for the anisotropic diffusion and the mean-field interaction of the particles. By numerically solving the Smoluchowski equation under moving boundary conditions, we obtain the spatiotemporal evolution of volume fractions and order parameters.

Surfactant effects on droplet dynamics and deposition patterns: a lattice gas model.

A coarse-grained lattice gas model is developed to study pattern forming processes in drying drops containing surfactant. By performing Monte Carlo simulations of the model, the coupled dynamics of surfactant and liquid evaporation and the resulting oscillatory dynamics at the contact line are elucidated. We show that the coupled drop dynamics and the resulting final deposition patterns can be altered by adsorption kinetics.

Instability deposit patterns in an evaporating droplet.

The characteristics of several patterns left after the evaporation of a particle-laden liquid droplet are investigated by using a coarse-grained lattice model. The model includes both evaporative convection and the Brownian motion of weakly interacting particles. The model is implemented by using a Monte Carlo method to investigate the different deposit patterns near the contact line.