Study on Ice Plug and Ferrofluid Pulled by a Magnet in a Microchannel

The field of microfluidics is fast developing with advances in MEMS, biotechnology and μ-TAS technologies. In various microfluidic devices, controlling the motion of liquid slugs and materials in a microchannel is necessary. In the biotechnology field, freezing of cells in a microchannel and transfer of frozen cells in a micro reactor are required. We previously studied the motion of liquid and air plugs by moving a ferrofluid plug electromagnetically. In this study, we focus on the formation and motion of an ice plug in a microchannel. First, an abrupt change from a supercooled water slug to the ice plug is observed. As the ice plug is heated and a water layer is produced between the tube wall and ice plug, the frozen ice plug is then moved in the microchannel by using a ferrofluid plug. By controlling the driving power exerted on the ferrofluid plug, the motion of the ice plug has been studied.