Micro-ring based manipulation of magnetized particles.

The micromanipulation of untethered magnetic particles facilitates actuation, assembly, and characterization of samples for micro- and nanotechnology applications. Conventionally, macro-scale electromagnets combined with visual servo control are employed to manipulate untethered particles. Here, we propose to employ a micro-ring actuator and a strategy based on parametric excitation for manipulation of magnetized particles against a surface in a liquid medium, which does not require visual feedback. Experimentally, the system has been employed to smoothly manipulate magnetic particles of diameter in the range 30-50 µm to move along predefined trajectories. Subsequently, the particles have been demonstrated to be manipulated into a conventionally inaccessible region beneath the re-entrant walls of a micromachined silicon chip.