Research Development of Multiple Valuable Imaging in Micro-Thermofluid Devices

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Rapid technological progress has required reliable measurement techniques for velocity and temperature in microspace, particularly in the biological or electrochemical engineering. This paper focuses on how to accomplish quantitative measurement techniques applicable to investigating thermofluid dynamics in a microchannel that is utilized in lab-on-a-chip and μTAS. Micro-resolution particle image velocimetry (micro-PIV) is one of promising techniques to measure fluid velocities in a microchannel using a time-averaging method in order to eliminate the effect of Brownian motion of sub-micron tracer particles on velocity detection, however, this technique has no ability to detect an unsteady flow that is frequently observed in microfluidic devices. A spatial averaged time-resolved particle tracking velocimetry method was proposed to measure velocity fields in a pulsating flow considering Brownian motion. Temperature measurements of a fluid flow in a microchannel were performed utilizing fluorescence, because the fluorescent intensity is strongly dependent on temperature. Using this temperature measurement system and micro-PIV it was found that the heat flux due to conduction is approximately fifty times that due to convection in a microchannel, therefore one has to consider the heat conduction in the design processes of microfluidic devices.