Catheter-Based Microrotary Motor Enabled by Ferrofluid for Microendoscope Applications

This paper reports the first microrotary motor enabled with a novel ferrofluid-based levitation mechanism 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. Two types of micromotors with 1.6-mm and 500-μm-sized rotors are designed, fabricated, and tested. The fabricated prototypes of the motors are successfully operated to rotate the prism mirrors integrated with the motors, with revolution rates as high as 1875 and 1500 r/min for the 1.6-mm and 500-μm rotor types, respectively. Thermal behaviors of the devices are also characterized and reported. The experimental results demonstrate the effectiveness of the motor design and indicate high potential for side-viewing microendoscopic applications.