Measuring Diffusion and Quenching in Microchannels

Abstract

Two-inlet microfluidic channels were fabricated using polydimethylsiloxane, and laminar fluid flow within them was visualised under epi-illumination using an inverted microscope. Analyte diffusion occurred across the channel width, and its concentration profile was extracted and analysed by a custom-written Java plugin within ImageJ to give the diffusion coefficient and quenching constant of various analytes. The measurements quantified extents of wall hindrance and the Butterfly Effect occurring in the microchannel, due to the presence of parabolic velocity profiles during flow. This analysis method is inexpensive, expedient, requires only small analyte volumes, and can be used to complement existing means of diffusion measurements requiring more elaborate equipment.