Electrokinetic Instabilities in Ferrofluid Flows

Instabilities in ferrofluids have so far been reported under the application of a magnetic field, which can be utilized to, for example, mix samples at small Reynolds numbers for microfluidic applications. We present in this work our recent experimental observations of instabilities occurring at the interface of electric field-driven ferrofluid and water co-flows. Such electrokinetic instabilities are produced primarily by the mismatch of electric conductivities of the two fluids. A two-dimensional numerical model is developed to compute the electric, flow and concentration fields, which is able to qualitatively simulate the onset and pattern of electrokinetic instabilities.