  Efficient drug delivery is a major challenge in modern medicine and
pharmaceutical research. Micrometer-scale robots have recently been proposed as
a promising venue to amplify precision of drug administration. Remotely
controlled microrobots sufficiently small to navigate through microvascular
networks can reach any part of the human body, yet real-time tracking is
crucial for providing precise guidance and verifying successful arrival at the
target. In vivo deep-tissue monitoring of individual microrobots is currently
hampered by the lack of sensitivity and/or spatio-temporal resolution of
commonly used clinical imaging modalities. We synthesized biocompatible and
biodegradable copper phosphate micro-flowers loaded with indocyanine green and
iron oxide nanoparticles to enable in vivo individual detection with
localization optoacoustic tomography. We demonstrate magnetic actuation and
optoacoustic tracking of these decorated micro-flowers at a per-particle level.
Functional super-resolution imaging achieved via tracking intravenously
injected particles provides a means of identifying microvascular targets and
quantifying blood flow, while the versatile carrying capacity can be further
exploited for transporting multiple types of drug formulations.
