Mobile microrobots have transformative potential in healthcare, enabling active medical interventions like targeted drug delivery and microsurgical tasks in hard-to-reach areas. However, achieving precise control and high-resolution imaging of cell-sized microrobots within the in-vivo vascular system remains a major barrier to clinical application. To address this, we propose using optoacoustic imaging for noninvasive, real-time detection and tracking of circulating microrobots.

In our work, we developed nickel-based spherical Janus microrobots, enhanced with gold conjugation to increase their near-infrared optoacoustic visibility. These cell-sized microrobots, available in diameters of 5, 10, and 20 micrometers, have been successfully detected in ex vivo tissue and in the blood-rich environment of murine cerebral vasculature. We demonstrated real-time 3D tracking and magnetic manipulation of the microrobots, setting the groundwork for safe, controlled use in clinically relevant intravascular environments [A].

This study also presents macrophage-based microrobots combining magnetic Janus particles with FePt nanofilms for actuation and bacterial lipopolysaccharides to stimulate tumor-targeting responses. These biohybrid microrobots, steered magnetically and tracked via optoacoustic imaging [B], show strong antitumor capabilities. In lab tests, they were directed toward tumor spheroids in soft-tissue-mimicking phantoms, significantly reducing tumor viability.

Additionally, we integrated a hybrid optoacoustic and focused ultrasound system to enable simultaneous imaging and actuation, achieving real-time 3D tracking and manipulation of particles within live mouse vasculature [C]. This approach validates the potential of combining imaging and actuation in a single platform for precise medical interventions, paving the way for diverse future applications in cancer treatment and minimally invasive surgery.