Analysis of single droplet dynamics on striped surface domains using a lattice Boltzmann method

Abstract

In this paper, the behavior of a micron-scale fluid droplet on a heterogeneous surface is investigated using a two-phase lattice Boltzmann method (LBM). The two-phase LBM permits the simulation of the time dependent three-dimensional motion of a liquid droplet on solid surface patterned with hydrophobic and hydrophilic strips. A nearest-neighbor molecular interaction force is used to model the adhesive forces between the fluid and solid walls. The solid heterogeneous wall is a uniform hydrophilic substrate painted with hydrophobic strips. The model is validated by demonstrating the consistency of the simulation results with an exact solution for capillary rise and through qualitative comparison of computed dynamic contact line behavior with experimentally measured surface properties and observed surface shapes of a droplet on a heterogeneous surface. The dependence of spreading behavior on wettability, the width of hydrophobic strip, initial location of the droplet relative to the strips, and gravity is investigated. A decrease in contact angle of the liquid on a hydrophilic surface may lead to breakup of the droplet for certain substrate patterns. The simulations suggest that the present lattice Boltzmann (LB) model can be used as a reliable way to study fluidic control on heterogeneous surfaces and other wetting related subjects.

Lattice Boltzmann method for microfluidics: models and applications

“…Different signs (positive or negative) of this controlling parameter are required to model wetting and nonwetting surfaces. This is also true for other LBM multiphase models (Chang and Alexander 2006). However, physically there is no such a clear boundary for surface wettability, as demonstrated by experimental observations (Gao and McCarthy 2008) and MD simulations (Nijmeijer et al 1990;Bertrand et al 2009).…”

Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications

“…There also exists a number of studies where the LB method is used to study wetting of droplets on a flat surface with heterogeneous wetting conditions (Dupuis and Yeomans 2004;Chang and Alexander 2006;Yan and Zu 2007;Huang et al 2008) or the capillary rise between parallel plates (Wolf et al 2010). In some references, the codes are validated by applying them to test problems with known analytical solution.…”

Thermal vibrational convection in a two-phase stratified liquid

“…Additional details concerning modeling two-phase fluids using the lattice Boltzmann method are found in Ref. 10. In the TLBM the fluid motion is computed using a two-particle distribution function approach proposed by He et al [11,12].…”

“…In the TLBM the fluid motion is computed using a two-particle distribution function approach proposed by He et al [11,12]. The two distribution functions satisfy the following equations for distribution functions ( , , ) t ξ r e and ( , , ) f t φ r e where e is a so-called microscopic velocity [8][9][10]11], r is the position and t is time.…”