Untethered Soft Machines and Robots by Printing Ferromagnetic Domains in Soft Materials

Soft active materials capable of transforming into programmed shapes in a remotely controllable manner can bring promising applications in diverse fields such as soft robotics and biomedicine. Several types of shape-programmable soft matter have been proposed but often limited to simple geometries and thus with limited functionalities. We introduce a method of printing ferromagnetic domains in soft materials to realize highly responsive and fully programmable soft active materials that quickly transform into multiple desired shapes in applied magnetic fields. We also discuss the mechanics of our printed magnetic soft materials and the model-based simulation, which enable us to design complex structures with multiple modes of programmed actuation while guiding the material design for optimal actuation performance. Combined with the flexibility in design and fabrication, the fast and dynamic response of our printed soft machines and robots provides a range of potential applications, especially in biomedical areas where remote actuation of such untethered devices can be useful. To open this new avenue, we present a set of demonstrations that exemplify the concept of untethered soft machines and robots in biomedical applications such as magnetically steered catheters and guidewires.