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 μm 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.