A Basic Study of a Straight-Flow Micromixing Device Utilizing a Very Thin Liquid Film

Abstract

Many kinds of passive and active mixers have been studied using micromixing principles, and many of them mainly depend on molecular diffusion as the source of the mixing. Therefore, using a small diffusive distance is a primary method of improving in micromixing. The study of straight-flow micromixing utilizing a gas-liquid free interface in our laboratory confirmed that regional changes in flow direction near the bubble played a definitive role in rapid mixing. To achieve fast mixing using these two effects, we developed a new micromixing device that utilizes a thin liquid film between two static bubbles. The size of the bubbles was larger than that of the channel cross section in a Y-type straight-flow microchannel. In this study, we discuss the formation and behavior of bubbles or liquid films on the basis of the results of bubble forming experiments, as basic research toward developing the new device. We conducted the experiments using several test channels that had different sizes and locations of bubbles, and using CFD (computational fluid dynamics) simulation, we calculated the mixing performance in different designs of the mixing device. As a result, we successfully achieved the formation of static bubbles and thin liquid films under the condition of a low Reynolds number of 0.17. In addition to confirming that our new mixing device can be applied under that condition, we found that it has a stable capability for mixing.