Microfluidic flow actuation using magnetoactive suspensions

The rheological behavior of magnetotactic bacterial suspensions is analyzed using a continuum kinetic theory. In both unbounded and confined geometries, the response of these suspensions under simple external flows can be controlled by applying a magnetic field and hinges in a subtle way on the interplay of magnetic alignment, rotation under shear, and wall-induced accumulation under confinement. By tuning magnetic field strength and direction, the apparent viscosity can either be enhanced or reduced, and the mechanisms for these trends are elucidated. In the absence of any applied flow, we further demonstrate the ability of magnetoactive suspensions to internally drive steady unidirectional flows upon application of a magnetic field, thus suggesting novel avenues for the design of microfluidic pumps and flow actuation devices.