Design of a Growing Robot Inspired by Plant Growth A novel design concept of expandable robotic arm inspired by plant growth is presented. The robot can construct its own structure by converting a type of fluidized material into a rigid structure at its growing point. The robot can extend its structure in multiple directions, and move through a winding space to reach a point, which is otherwise difficult to access. The robot with the rigid structure can also bear a significant load, has a plate to attach an endeffector, and can transport an object. The robot satisfies three key functional requirements that are characteristic to plant growth. First, the robot is capable of transporting structural materials to its growing point. Second, the robot is capable of transforming the material into a rigid structure. Third, it is capable of steering its growing point so that it is expanded in a desired direction. A proofof concept prototype is then presented that consists of a special sprocket chain that can be switched between flexiblefluidized and rigid states, a winch that can pulltransport the chain, and a steering system to direct the growing direction. Unlike plants, this growing robot can retract its extended body, and can extend in a different direction. The prototype demonstrates that it meets all the functional requirements, and that it can make sharp turns and move through obstacles.

Characterizing Environmental Interactions for Soft Growing Robots Soft, tipextending devices, or xe2x80x9cvine robots,xe2x80x9d are a promising new paradigm for navigating cluttered and confined environments. Because they lengthen from their tips, there is little relative movement of the body with the environment, and the compressible nature of the device allows it to pass through orifices smaller than its diameter. However, the interaction between these devices and the environment is not well characterized. Here we present a comprehensive mathematical model that describes vine robot behavior during environmental interaction that provides a basis from which informed designs can be generated in future works. The model incorporates transverse and axial buckling modes that result from growing into obstacles with varying surface normals, as well as internal pathdependent and independent resistances to growth. Accordingly, the model is able to predict the pressure required to grow through a given environment due to the interaction forces it experiences. We experimentally validate both the individual components and the full model. Finally, we present three design insights from the model and demonstrate how they each improve performance in confined space navigation. Our work helps advance the understanding of tipextending, vine robots through quantifying their interactions with the environment, opening the door for new designs and impactful applications in the realms of healthcare, research, search and rescue, and space exploration.