Reversionary rotation of actuated particles for microfluidic near-surface mixing

The off-axis motion of particles actuated by axial magnetic or gravitational forces is studied in fluidic channels. Single actuated superparamagnetic micro-particles starting from channel walls travel towards the channel center and show unforeseen reversionary rotation phenomena. Different stages of co- and counter-rotation are observed in both micro- and macro-scale experiments and are analyzed by means of numerical fluid-dynamics models. The related microfluidic near-surface mixing performance of the rotating actuated particles is discussed.