The fantastic voyage of microrobots towards medical applications

The controlled and targeted delivery of pharmaceutical agents and therapies are major challenges in pharmacology and medicine. To date pharmaceutical agents are given systemically undermining their effectiveness and leading to side- and off-target effects. Even though passive targeting by the use of antibody-conjugated micro- and nanoparticles can increase the agglomeration of different drugs and therapeutic at their target side, still there is a lot of uptake in other organs such as the liver or spleen. Also, physical therapies like radiation therapy suffer from low specificity to the actual therapeutic target. Therefore, active delivery approaches are needed to overcome current limitations of many pharmaceutical agents and therapies. In the last decade microrobots with a size below 20 µm have advanced as possible next generation active delivery systems. A versatile set of possible applications for microrobots ranging from drug delivery, theragnostic, and active contrast agents to tools for physical therapies has been demonstrated. Due to miniaturization-limitations typical design principles for robots do not apply for microrobots. With state-of-the-art electronic systems no on-board computation can be implemented into cell-sized robots. Consequently, new design paradigms and solutions for on-board actuation, powering, sensing, computing and communication need to be identified.