Magnetic responsive brushes under flow in narrow slits: external field control of brush structure and flowing particle mixture separation

In the present work magnetic brushes under flow conditions and confined inside narrow slits have been studied using Langevin dynamics simulations. It has been observed that the structural properties of these confined magnetic brushes can be tuned via the application of an external magnetic field, and this control can be exerted with a relative low content of magnetic colloidal particles in the filaments that form the brushes (20% in the present study). The potential of these brushes to perform a separation process of a size-bidisperse mixture of free non-magnetic colloidal particles flowing through the slit has been also explored. Numerical results show that it is possible to induce a two-fold effect on the bidisperse particle flow: a lateral separation of the two types of flowing colloidal particles and an enhancement of the differences in their velocities. These two features are key elements sought in separation processes and could be very relevant in the design of new chromatographic columns and microfluid separation devices.