Condensation of droplets on nanopillared hydrophobic substrates

Abstract

Using the constrained lattice density functional theory, we investigated the mechanism of droplet condensation, including droplet nucleation and growth, on nanopillared substrates. We find that similar to a macroscopic droplet on such a substrate, the critical nucleus also exhibits either the Wenzel or Cassie wetting state, depending on both the pillar height and the interpillar spacing. Our calculations show that there exists a critical value of the interpillar spacing, above which the critical nucleus is always in the Wenzel state and the pillared substrate always promotes the nucleation as compared to the smooth substrate, regardless of the pillar height. Below the critical interpillar spacing, however, the pillars always inhibit the nucleation, and the wetting state of the critical nucleus depends on the pillar height. Furthermore, our results demonstrate that the wetting state of the critical nuclei is not necessarily the wetting state of the formed microdroplets: droplets originated from the critical nuclei in the Wenzel state may change into the Cassie state spontaneously during the droplet growth process if the pillar height is greater than a critical value.

Mechanism of two-step vapour–crystal nucleation in a pore

“…Heterogeneous nucleation of liquids and crystals has been studied both theoretically and in simulation for a variety of geometries such as nucleation on planar walls [7,8] and in slit pores [9][10][11][12], on cylinders [13][14][15], patches [16,17], patterned templates [18][19][20][21], spheres [22][23][24] and in pores [25][26][27][28]. Experimental studies include colloidal crystallisation on patterned templates [4,29,30] and spherical impurities [31,32].…”

A review of recent theoretical and computational studies on pinned surface nanobubbles

“…The lattice density functional theory (LDFT) [51][52][53][54][55][56][57] based on a simple cubic lattice gas model provides a very simple but efficient method to investigate the behavior of simple fluids at a molecular level, and has been widely used to study the capillary condensation and evaporation [51][52][53][54][55] , the vapor-liquid nucleation [58][59][60][61][62] , the water bridges [63] and the wetting of solid surface [64,65] . In these years, LDFT has also been used to study the pinned surface nanobubbles [34,[66][67][68][69][70] .…”

Constrained lattice density functional theory and its applications on vapor–liquid nucleations

“…Therefore, CLDFT was proposed to obtain the nucleus morphology and nucleation barrier [24][25][26][27]. This method introduces an appropriate constraint into classical LDFT to achieve a transition state, and its validity has been proved by recent investigations [28,29].…”