Developing medical microrobots that can be remotely steered inside the body by an external operator while the robot semi-autonomously responds to physiologically relevant chemical and biological stimuli presents multi-dimensional challenges concerning design, fabrication process, and encoding functional capabilities. Integration of 3D microprinting strategies with tailor-made stimuli-responsive materials can enable responsive and functional medical microrobots. In this direction, we have explored the potential of the two-photon absorption-based 3D microprinting for controlled photopolymerization, which enables both space and time control over the 3D fabric of a microstructured material. We have developed various synthetic and bio-derived material compositions compatible with 3D microprinting [ ]. Introduction of chemical versatility to the 3D-printed microrobot bodies would allow further functionalities to be encoded, leading to novel design opportunities for microrobots. To prove the concept, we showed the first 3D bullet-shaped bubble-propelled micromotor, with compartmentalized placement of the catalyst and effect. Next, we applied this fabrication method to develop a microrobotic cell delivery platform for therapeutic stem cells where the cellular fate is controlled by the reconstructed niche within the cell transporter [ ]. Also, we have developed mobile microrobots exhibiting one-way and two-way shape-memory behaviors by responding to various external and local stimuli: metastatic biomarkers, magnetic fields, temperature, pH, and calcium ions [ ].
3D printing has provided us with design leverage for optimized structures and material compositions to improve biocompatibility by minimizing unintended interactions with the live environment. Our conclusions enabled by the systematic investigations of structure and material-based microrobotic design parameters pave the way for multifunctional, biocompatible, and personalized microrobots for medical applications.