Pressure-driven and other flows in microstructure optical fibres for microfluidics

Abstract

Microfluidics are important micro-scale devices that can be used to manipulate very small volumes of fluids on the order of nano- to femto-liters. The control and sorting of nano-particles is a primary goal using this technology. There is particular interest in the use of microstructure optical fibers for the transfer of fluids, whereby the guided light interacts with a fluid in the region of the air-hole structure. We study the fluid transport capabilities of microstructure fibers with cross sections containing circular or elliptical holes, considering the effects of flow rates, fluid viscosity, and the channel diameter. The role of heat flux is considered in relation to the fluid characteristics. We solve the time-dependent Navier-Stokes equations and the convection-diffusion equation. This work is of importance as one cannot assume that the flow dynamics in microstructure fibres will be the same as conventional micro-fluidic channels. Through the study of the heat transfer, for pressure-driven and other flows and for low Reynolds numbers, we confirm anticipated behaviour of the fluids in the micro-channel structure.