Tracking of a Magnetically Navigated Millirobot With a Magnetic-Field Camera

A significant progress has been made in the development of magnetic micromanipulation for minimally invasive surgery. The development of systems to localize millimeter-sized robots during magnetic manipulation without line-of-sight detection remains, however, a challenging task. In this study, we focused on the development of a tracking system aiming to fill this gap. A robot, which consists of a cylindrical magnet of 1-mm diameter, is localized using a 2-D array of 3-D magnetoresistive sensors. The system, also called magnetic-field camera (MFC), provides tracking of the robot with a refresh rate of 2 Hz. The developed tracking algorithm reaches a mean absolute error (MAE) for the position and the orientation of, respectively, 0.56 mm and 5.13° in 2-D. This system can be added to the existing magnetic manipulation systems (MMSs) allowing closed-loop control of the navigation. The performances of the MFC are not affected by an exposure to strong magnetic fields. Exposures up to 3 T have been validated. Increasing the integrability of the MFC into MMSs. The presented tracking system makes it possible to target applications, such as minimally invasive eye surgery or drug delivery. The high spatial and magnetic resolutions allow the tracking of magnetic particles, down to 200-
$\mu \text{m}$
diameter, when placed close to the surface. The system could also be suitable for the localization of small objects for 2-D biomanipulation.