This article presents strategies for the passive path and morphological adaptation of a plant-inspired growing robot that can build its own body by an additive manufacturing process. By exploiting the soft state of the thermoplastic material used by the robot to build its structure, we analyzed the ability of the robot to change its direction of growth without the need for specific cognition and control processes. Obstacle avoidance is computed by the mechanics from the body-environment interaction. The robot can passively adapt its body to flat obstacles with an inclination of up to 50° with resulting reaction forces of up to ∼10 N. The robot also successfully performs penetration and body adaptation (with 30° obstacle inclination) in artificial soil and in a rough unstructured environment. This approach is founded on observing plant roots and how they move and passively adapt to obstacles in soil before they actively respond followed by cell division-based growth.
Keywords: 3D printing; additive manufacturing; biologically inspired robots; growing robots; soft material robotics.