Transport of loaded and unloaded microcarriers in a colloidal magnetic shift register.

We demonstrate the dispersion free digital transport of emulsion droplets and biological cells in an aqueous solution using paramagnetic colloidal particles above a uniaxial magnetic garnet film. Magnetic modulations above the stripe domain pattern induce a step-wise transport of paramagnetic particles dispersed in water and deposited on the surface of the film. Capillary or hydrodynamic interactions are then used to couple the cargo to the paramagnetic beads. We achieve full control of the cargo motion up to velocities in the 100 microm/s range.