Visualization of Convective Mixing in Microchannel by Fluorescence Imaging

Two-dimensional temperature measurement techniques were developed using fluorescence in order to investigate convective mixing phenomena in microspace. The present study focused on the spatial and temperature resolution using a fluorescence dye, i.e., Ru(bpy)₃²⁺, whose fluorescence intensity is strongly dependent on temperature, yielding a precise measurement in microspace. The temperature resolution obtained from this study showed ±0.26K in the range from 293K to 334K at the spatial resolution of 5×5 μm The present work utilized a T-shaped microchannel with two inlets, which was fabricated with silicone elastamer, i.e., polydimethylsiloxane (PDMS) using the replica molding technique. Velocity measurements in the junction area of the microchannel were performed by a micro-resolution particle image velocimetry. It is observed that the conduction heat flux is more dominant than the convection heat flux when two fluids, at different temperature merged together in the junction area. The measurement techniques in microspace accomplished in the present study has an ability to visualize and to investigate mass and thermal diffusion in the microchannel, which will be contribute significantly to develop the microdevices.