Surprising Microbeads Focusing in a Microchannel

― Automatic Alignment of Microbeads into Lines ―

抄録

A surprising microbeads focusing is observed inside a microfluidic channel without using any control device. The beads are aligned into multiple lines parallel to the channel walls in a straight channel when the flow rate reduced from 3 μm/ms to 0.05 μm/ms. Possible causes of such a surprising focusing have been investigated from different viewpoints, and acoustic standing wave turns out to be the most possible reason. A frequency analyzer is utilized for inspecting wave signals in the experimental environment. We found that the linear slider, which is for controlling the flow pressure, generates a sequence of high-frequency signals. The analysis of the focusing and surrounding frequency are discussed.