Abstract: Embodiments herein include a scanning apparatus for detecting target particles present within a ferrofluid, where the scanning apparatus can be used in a microfluidic system. The methods and structures described herein also include, for example, a scanning device comprising an optical system, a first magnet disposed on a first side of the optical system, where the first magnet can be non-rotatable, a second magnet disposed on a second side of the optical system, opposite the first magnet, where the second magnet can be rotatable, and a lever arm coupled to the second magnet, where the lever is capable of rotating the second magnet.