Magnetic Resonance Guided Navigation of Untethered Microgrippers.

Microsurgical tools offer a path to less invasive clinical procedures with improved access, reduced trauma, and better recovery outcomes. There are a variety of rigid and flexible endoscopic devices that have significantly advanced diagnostics and microsurgery. However, they rely on wires or tethers for guidance and operation of small end-effector tools. While untethered physiologically responsive microgrippers have been previously shown to excise tissue from deep gastrointestinal locations in animal models, there are challenges associated with guiding them along paths and moving them to specific locations. In this communication, the magnetic dipole moment of untethered thermally responsive grippers is optimized for efficient coupling to external magnetic resonance (MR) fields. Gripper encapsulation in a millimeter sized wax pellet reduces the friction with the surrounding tissue and MR Navigation (MRN) of a 700 µm sized microgripper is realized within narrow channels in tissue phantoms and in an ex vivo porcine esophagus. The results show convincing proof-of-concept evidence that it is possible to sequentially image, move, and guide a submillimeter functional microsurgical tool in tissue conduits using a commercial preclinical MR system, and when combined with prior demonstrations of physiologically responsive in vivo biopsy are an important step towards the clinical translation of untethered microtools.