Magnetic separation techniques are commonly used to separate biological molecules and micro-organisms from complex fluids. Over the last few decades, however, there have been virtually no monumental advances in the field of magnetic separation. Most work has focused on incremental improvements by using stronger fields and field gradients to achieve more efficient separation. Here the authors describe the development of a fundamentally new and different approach to magnetic separation, which uses a traveling magnetic field wave generated on the surface of a microfluidic device that can transport particles as shown in (A). This traveling wave can be used to tune the mobility of superparamagnetic beads, and in the process separate different types of beads with extremely high resolution as shown by (B). We present experimental results that demonstrate the possibility of implementing effectively “infinite” separability between two marginally different colloidal species. By “infinite” separability, we mean that it is possible to cause certain particles to move across the chip whereas other particles are immobilized. In this manuscript, we show how magnetic beads of different sizes can be separated on the same chip. To our knowledge, there is no existing magnetic separation technique that can separate these highly similar materials with such fine resolution. In addition, we provide a theoretical derivation for the physics of the separation process which can predict the velocity of the bead as a function of the external driving frequency.