Submillimeter Magnetic Microrobot Tracking Using an Integrated Ultrasound and Photoacoustic Imaging System

This paper presents the proof-of-concept study on a non-invasive tracking of submillimeter sized micro-robotic objects by using combined ultrasound and photoacoustic imaging. Tracking one single microscale untethered magnetic microrobot through the integrated ultrasound and photoacoustic (USPA) imaging will allow for accurate real-time controlling the manipulation of the microrobot in optically non-transparent biological tissues. In this work, the magnetic microrobot prototypes are made from photoresist mixed with nickel particles. Single microrobot agent is set in a fluid environment bounded by an opaque phantom. The experimental results prove that the current microrobot prototypes smaller than 100 mu m can be detected by USPA imaging through 15 mm thick opaque phantom, both statically and in a motion of speed approximately 1.5 mm/s. The further investigation of this concept will advance the integration of both non-invasive magnetic manipulation and USPA tracking of the microrobot, targeting the real biomedical applications in the tiny enclosed workspaces.