Manipulation of magnetocapillary flow of ferrofluid in a microchannel

We report the influence of stationary and moving permanent magnets on the magnetocapillary flow of ferrofluid in a microchannel. With the stationary magnet placed at the microchannel exit, a sudden increase in the meniscus velocity was observed when the ferrofluid meniscus comes under the influence of the magnet. In case of the moving magnet, for a fixed initial magnet location, the meniscus velocity remains constant when the meniscus is closer to the magnet and is directly proportional to the magnet velocity. For a given magnet velocity, irrespective of the initial location of the magnet, a fixed steady state meniscus velocity is achieved. We demonstrated forward motion, stopping and reverse motion of the ferrofluid meniscus by controlling the motion of the magnet, which could find applications in biological and chemical analysis.