光誘起局所粘性分布下におけるマイクロ流動構造の解明(流体工学,流体機械)

抄録

In microfluidic device such as lab-on-a-chip, flow behavior of liquid is governed by its property, especially by viscosity, due to increasing surface-to-volume ratio. Therefore, an appropriate control on the viscosity can be an effective fluid handling method unique for the microdevice. The aim of the present study is an investigation of the effect of inhomogeneous viscosity on the microflow structure. This study relies on the photothermal technique to induce the local viscosity distribution in the flow field in a microchannel. Optically-induced temperature rise causes corresponding distribution of the viscosity owing to the inherent temperature dependence. We have developed an experimental system to perform the local heating into the microflow and to measure the temperature and velocity fields. Micro-LIF (laser-induced fluorescence) and micro-PIV (particle image velocimetry) are used for the temperature and velocity measurement, respectively. As the results, flow velocity is locally increased at a high temperature area heated by the focused laser beam. Around the hot region, accompanying flow is observed. This change in the flow behavior is attributed to the local reduction of the liquid viscosity. The agreement between the experimental results and the numerical simulation considering the temperature-dependent property elucidated that the primary factor to induce the flow structure variation in microchannel was the local nonuniformity of the viscosity.