Evaluation of Wettability of Micro-fabricated Solid Surface Using CFD Simulation

Abstract

We verify applicability of a computational fluid dynamics (CFD) method based on a phase-field model (PFM) to direct numerical simulation of microscopic droplet motion on structured and heterogeneously wettable solid surfaces. Instead of the Cahn–Hilliard equation, the conservative Allen–Cahn (CAC) equation is adopted to calculate the advection and construction of diffusive interfaces. A numerical scheme based on the lattice Boltzmann model is employed to solve the Navier–Stokes equations of fluid coupled with the CAC equation in one-field formulation for an immiscible incompressible isothermal two-phase fluid system with equal densities and viscosities. Droplet motions under external force are simulated on grooved, square-pillar-arrayed, and flat sold surfaces in three dimensions. From the numerical results in qualitative comparison with available experimental data, it is confirmed that the PFM-CFD method can be used to simply evaluate the wettability of micro-fabricated solid surfaces with patterned 3D structures for efficient evaluation and optimal design by analysis of the functions of micro-fluidic devices in various fields of science and engineering.