A hydrodynamic switch: Microfluidic separation system for magnetic beads

In this work a device for separating small magnetic particles in continuous flow is introduced, consisting of two microfluidic channels that are connected by a junction channel. Applying two different flow rates, particles can be separated combining hydrodynamic and magnetophoretic effects. The two different flow rates introduce an additional degree of freedom that enables the microfluidic geometry to act as a hydrodynamic switch that can overcome diffusive contributions making the device applicable for particles of the size scale below 100 nm. Theoretical predictions based on finite element methods are compared to experimental observations.