Visualization of convective mixing in microchannel by fluorescence imaging

A two-dimensional temperature measurement technique was developed using fluorescence in order to investigate convective mixing phenomena in a microspace. The present study focused on the spatial and temperature resolution using a fluorescence dye, i.e., Ru(bpy)₃²⁺, whose flutrescence intensity is strongly dependent on temperature, yielding a precise measurement in the microspace. The temperature resolution obtained from this study showed ±0.26 K in the range from 297 K to 334 K 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 using the replica molding technique. Velocity measurements in the junction area of the microchannel were performed by a micro-resolution particle image velocimetry. It was observed that the conduction heat flux was 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 have an ability to visualize and to investigate mass and thermal diffusion in the microchannel, which will contribute significantly to develop the microdevices.