Non-invasive Photoacoustic Imaging of Magnetic Microrobot through Deep Non-Transparent Tissue

This paper presents the proof-of-concept study on a non-invasive microrobot technology that incorporates the frontier submillimeter magnetic microrobot with the burgeoning photoacoustic imaging. Tracking one single untethered magnetic microrobot through the integrated ultrasound and photoacoustic (USPA) imaging will allow for real non-invasive microrobot operation in the non-transparent biological tissues. In this preliminary work, the magnetic microrobot prototypes are made from photoresist mixed with nickel particles. Single microrobot agent is set in fluid environment bounded by non-transparent phantom. The experimental results prove that the current microrobot prototypes down to smaller than $100 \mu m$ can be detected by USPA imaging through $25 mm$ thick opaque phantom, both statically and in a motion of speed approximately $1.2 {mm/s}$. 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 workspace.