Numerical Study on Droplet Sliding across Micropillars

Abstract

Droplet sliding on surfaces is an important phenomenon since it widely happens in microfluidic industry. In this article, we simulate droplets sliding across micropillars on smooth substrates to test how the pillars with different intrinsic wettability influence the movement of droplets. The simulation is performed using a particle-based numerical method, many-body dissipative particle dynamics (MDPD). The simulated results show that the heterogeneous area (built by arranged micropillars) can influence the dynamical contact angles significantly. Both the advancing and receding contact angles increase when the droplet front slides on the heterogeneous area, and their difference is also enlarged, thus the contact line may be pinned. The droplet shows a creeping motion style when its front climbs over each pillar. We also find when the droplet enwraps all pillars, the composite liquid/solid surfaces have no effect on the advancing and receding contact angles. The outcomes support the viewpoint that the wettability is a contact-line-based problem instead of a contact-area-based one.

A dissipative particle dynamics method for arbitrarily complex geometries

“…6(a) we observe that the transient velocity profiles are in an excellent agreement with the analytical solution given by Eq. (13), which indicates that the boundary method can provide accurate no-slip boundary condition on the wall surface. Furthermore, Fig.…”

“…To this end, a coarse-graining approach eliminates fast degrees of freedom and drastically simplifies the dynamics on atomistic scales, while providing a cost-effective simulation path to capturing the correct properties of complex fluids at larger spatial and temporal scales beyond the capacity of conventional atomistic simulations [4]. In recent years, with increasing attention on the research of soft matter and biophysics [5], coarse-grained (CG) modeling has become a rapidly expanding methodology especially in the simulations of polymers [6,7,8], colloidal suspensions [9,10,11], interfaces of multiphase fluids [12,13,14], cell dynamics [15,16,17], blood rheology [18,19,20] and biological materials [21,22,23].…”

Nanoparticle-mediated evaporation at liquid–vapor interfaces

“…MDPD is a coarse-grained, particlebased computational method that can effectively simulate multi-phase, multi-component systems on the mesoscale and captures correct hydrodynamic behavior. [25,[36][37][38][39][40][41][42][43] MDPD models a volume of fluid as individual beads, and each bead represents a cluster of molecules. The evolution of the entire system over time is dictated by the motion of beads, which is governed by Newton's…”

Hydrodynamic Interactions and Entanglements of Polymer Solutions in Many-Body Dissipative Particle Dynamics

“…Many-body dissipative particle dynamics [30,32,33,34,41,42] is used to model polymer solutions with volume fractions ranging from 0.008 to 0.7, representing dilute solutions to semidilute solutions. MDPD is a mesoscopic particle-based method that can effectively model multi-phase, multi-component systems and captures correct hydrodynamic behavior [35,39,40,43,44,45,46,47,48,49]. In MDPD, a volume of fluid is modeled by coarse-grained beads, and each bead represents a cluster of molecules.…”

“…A recently developed variation, many-body dissipative particle dynamics (MDPD), further extends DPD’s capabilities to producing the liquid–vapor coexistence and simulating evaporation process [30,31,32,33,34,35], which is a promising step toward modeling solution-based processing of polymeric materials. Despite many successful MDPD simulations [35,36,37,38,39,40], there is no report on the parameterization of MDPD interaction parameters [37,41] for the liquid–vapor coexistent systems. More importantly, a comprehensive study of the conformation and dynamics of polymer chains in solutions is lacking.…”