Ferrofluid-assisted micro rotary motor for minimally invasive endoscopy applications

This paper reports a micro rotary motor that is enabled with magnetic fluid called ferrofluid used as an extremely simple, miniaturized bearing material for microendoscopy applications. The ferrofluid bearing is magnetically sustained on the permanent magnet rotor that is levitated by the bearing layer inside a tubular substrate, an endoscope catheter. The levitated rotor is electromagnetically driven by two photo-defined meander-type coils formed around the outer walls of the catheter that enables 90°-step angular actuation of the rotor. The fabricated prototype with the rotor coupled with a 1-mm-sized prism mirror is revealed to provide both step-wise and continuous rotations with revolution rates up to 1875 rpm, verifying the effectiveness of the bearing and motor mechanism. The prototype device is operated to demonstrate its ability of endoscopic imaging in an experimental model.