Imaging and control of nanomaterial-decorated micromotors

Micro-and nanorobots have the potential to perform non-invasive drug delivery, sensing, and surgery in living organisms with the aid of diverse medical imaging techniques. To perform such actions with microrobots require high spatiotemporal resolution tracking methods with real-time closed-loop feedback. Photoacoustic imaging (PAI) has appeared to be promising for the imaging of microrobots in deep tissue with better contrast. The precise maneuvering and function control of micromotors demands the combination of both deeptissue imaging and their control. Here, we show the motion behavior of the micromotors in a parametric study using closedloop control with optical feedback. We also present different strategies to overcome the current limitations of PAI to track micromotors with improved contrast by the use of dedicated contrast agents (Au nanorods (AuNRs) and Au nanostars (AuNSs)) and the proper selection of the transducer according to the penetration depth, and finally, we discuss the possibility to employ trans-illumination settings.