Axial particle displacements in fluid slugs after passing a simple serpentiform microchannel

In this work, we designed a simple microchannel to separate particles in fluids by size. We found that mixtures of polystyrene 2 and 0.5 μm particles in a fluid slug can be differentiated by size after passing a long serpentiform microchannel. In contrast to the tubular pinch effect, which separates the particle in radial direction, we found that the particle suspensions in fluid slugs are displaced along the flow directions. The separation performance increases with the increasing flow velocity. The feature of differentiation along the flow directions in our device leads to the result that the separation process can be easily improved by stretching the slug before cutting the slug into pieces. Furthermore, the alternative air slugs between working fluid slugs can also prevent clogging inside the microchannels.