Time correlated fluorescence characterization of an asymmetrically focused flow in a microfluidic device

In this study, we explore and model the behavior of a prototype microfluidic device which employs two non-mixing fluids (sheath and inlet fluids) displaying an asymmetric focused flow, in the presence of a fluorescent dye. Fluorescence correlation spectroscopy is employed, allowing the precise measure of flow speeds across the channels and of the concentration profile of the central focused flux along the flow direction. The system is modeled via a standard Navier–Stokes finite-element approach, coupled to convection–diffusion equations for the solute. Simulations reproduce accurately the shape, the position, and the width of the velocity and concentration profiles along the central channel and across the transversal and vertical sections of the microfluidic device. The observed asymmetric flow with respect to the center of the channel is reproduced numerically with an error in the position determination smaller than 1%.