Convection and diffusion in a micro-flow injection system

Five micro-structures were used to study the effect of the convection and diffusion behavior (dispersion) of a dye in a micro-flow system. Besides a straight manifold, manifolds with curved bends and manifolds with rectangular bends were constructed. The dispersion resulting from hydrodynamic injection of a dye sample in a micro-flow system was measured for two structures. The detection was done spectrophotometrically. The sample dispersion through the five structures was also investigated with a computational fluid dynamics (CFD) software tool. Both the numerical and experimental results show that a structure with 40 rectangular bends exhibits a slightly larger dispersion compared to a straight channel or a channel with curved or a few rectangular bends. However, the difference in dispersion is minimal. The use of sharp bends to establish a flow system with a certain traveling distance within a small area has minimal effects on the dispersion of a sample under the conditions described in this paper. The general numerical model allows the calculating of the flow profile, pressure distribution and the concentration distribution of the sample, three dimensionally, throughout an arbitrary channel.