Self-pinning of a nanosuspension droplet: Molecular dynamics simulations

Abstract

Results are presented from molecular dynamics simulations of Pb(l) nanodroplets containing dispersed Cu nanoparticles (NPs) and spreading on solid surfaces. Three-dimensional simulations are employed throughout, but droplet spreading and pinning are reduced to two-dimensional processes by modeling cylindrical NPs in cylindrical droplets; NPs have radius R_{NP}≅3nm while droplets have initial R_{0}≅42nm. At low particle loading explored here, NPs in sufficient proximity to the initial solid-droplet interface are drawn into advancing contact lines; entrained NPs eventually bind with the underlying substrate. For relatively low advancing contact angle θ_{adv}, self-pinning on entrained NPs occurs; for higher θ_{adv}, depinning is observed. Self-pinning and depinning cases are compared and forces on NPs at the contact line are computed during a depinning event. Though significant flow in the droplet occurs in close proximity to the particle during depinning, resultant forces are relatively low. Instead, forces due to liquid atoms confined between the particles and substrate dominate the forces on NPs; that is, for the NP size studied here, forces are interface dominated. For pinning cases, a precursor wetting film advances ahead of the pinned contact line but at a significantly slower rate than for a pure droplet. This is because the precursor film is a bilayer of liquid atoms on the substrate surface but it is instead a monolayer film as it crosses over pinning particles; thus, mass delivery to the bilayer structure is impeded.

Self-Propulsion and Shape Restoration of Aqueous Drops on Sulfobetaine Silane Surfaces

“…However, the contact line motion stops and the wetting area remains unchanged as shown in Figure . This phenomenon is referred to as self-pinning on a total wetting surface due to solute addition …”

“…This phenomenon is referred to as self-pinning on a total wetting surface due to solute addition. 50 According to the behavior of spontaneous spreading of a pure water drop on the SBSi surface, one has a positive spreading coefficient defined 27 as S = γ sg − (γ sl + γ lg ). Here γ sg , γ sl , and γ lg represent the interfacial tension between solid−gas, solid−liquid, and liquid−gas phases, respectively.…”

Joint effect of advection, diffusion, and capillary attraction on the spatial structure of particle depositions from evaporating droplets

“…There are several discrete models, which explicitly describe the dynamics of each particular particle. These models are usually based on Monte Carlo or molecular dynamics methods [33,41,[43][44][45][46][47]. Some Monte Carlo based models are lattice models [48][49][50], and some are not [27,51,52].…”

Surfactant Control of Coffee Ring Formation in Carbon Nanotube Suspensions

“…This accumulation of particles at the contact line could also be physically responsible for the midway pinning event. 7,59,60 Finally, Figure 2D shows the evaporation data from a typical coffee ring deposit produced in this research. As expected, the CCR evaporation mode dominates this profile with the contact area remaining constant as evaporation proceeds.…”