An LMPA-based Magnetically-Actuated Growing Robot for Medical Applications

Growing robots are a subset of continuum robots with the main distinctive feature the fact that material is added from the tip instead of from the base. Currently, growing robots rely primarily on material deposition through filament printing or eversion using pneumatic circuits which may be too bulky or unsafe for applications inside the human body. In this paper, a proof of concept for a novel growing robot mechanism is presented. A variable stiffness tube (VST) based on low melting point alloy (LMPA) is developed to act as the growing element and the direction of robot growth can be guided using magnetic fields. A prototype is built to test the concept and is evaluated through experiments. Effects of Joule heating on the temperature within the VST are studied, as well as the stiffness variation of the VST when the LMPA transitions from solid to metal phase. The magnetic interaction is modeled and a system of external system of magnets is developed to achieve wireless guidance of the robot head. The growing mechanism of the robot via magnetic actuation is demonstrated through benchtop experiments where it is guided through straight and curved paths.