Regime dynamics of droplet behavior in hydrophilic contraction microchannel

Abstract

The droplet-based microfluidics technology achieves precise control over the behavior of droplets by designing the microchannel, controlling the flow, and managing the interactions of liquids. In this study, three-dimensional (3D) numerical simulations were conducted to investigate the behavior of droplets in a hydrophilic microchannel. With a hydrophilic microchannel, both wetting characteristics and microchannel geometry play a significant role in influencing the motion and behavior of droplets. The research introduces various droplet behavior regimes influenced by the contact angle (θ), capillary number (Ca), and viscosity ratio (λ), demonstrating that the influence of the hydrophilic microchannel occurs only at low capillary numbers. A predictive model for the critical capillary number to transition between contact and non-contact behaviors with the microchannel surface is proposed, described as follows: \(Ca>f\left(\lambda \right)({a}_{1}C+{a}_{2})\). This research provides valuable insights for liquid-phase system analysis devices that can analyze and manipulate fluids in a hydrophilic microchannel.