An empirical model for lateral flow in horizontally stratified flows

Lateral flow in microfluidic channels are of utmost importance. They are the main mechanism and/or challenge in many microfluidic applications. Despite this, there is a dearth of design rule of thumbs or mathematical models to predict the characteristics of the lateral flow. The lateral flow can be either caused by channel geometry or flowing fluid inhomogeneity. The aim of the present study is to provide a much-needed model for fluid inhomogeneity-induced lateral flow in the form of an empirical dimensionless model. The model is based on a numerical model which is in turn validated by experiments. The experiments are carried out by fabricating a microfluidic chip and observing the 3D structure of the flow under fluorescent confocal microscope. Based on the results, it is found that a single model, based on Grashof and Reynolds numbers, is capable of modeling the lateral flow due to fluid inhomogeneity regardless of the inhomogeneous property. The empirical model is capable of predicting the rotation caused by the lateral flow within 10% and is valid in lateral flows caused by either, diffusion or density inhomogeneity in the supplied liquid. The results provided here can be used with ease to improve the design of microfluidic devices dealing with lateral flow, density disparity, mixing, and chemical reaction.

Automated summary

Lateral flow is crucial in microfluidic applications, but there is a lack of design rules or mathematical models to predict its characteristics. This study provides an empirical dimensionless model for lateral flow induced by fluid inhomogeneity and validates it through experiments. The model accurately predicts the rotation caused by lateral flow and is applicable to various types of fluid inhomogeneity. The results can be used to improve the design of microfluidic devices dealing with lateral flow, density disparity, mixing, and chemical reaction.