A novel miniaturized fold-enabled soft growing robot for navigation in confined environments

Soft growing robots offer unique advantages in confined spaces due to their inherent compliance. However, in small-scale applications, the miniaturization of end-effectors and steering mechanisms poses major obstacles, impeding the synchronized extension of sensors and actuators and limiting effective directional control and flexibility. In addition, the high pressure required for growth introduces significant challenges for both actuation and control. To tackle these limitations, we propose the concept of fold-enabled growth and develop prototypes soft growing robots based on this approach. Fold-enabled growth is a mechanism that facilitates robotic extension through the deployment of pre-folded material. The prototype features two implementations that store the folded material at the robot’s base and tip, respectively, thereby minimizing structural dimensions and enabling seamless integration of sensors. They employ pre-bending in combination with pneumatic artificial muscles and tendon actuation to navigate confined spaces. This design integrates environment-driven navigation with active steering strategies, greatly enhancing the robot’s compliance and adaptability in confined environments. Compared to traditional eversion-based growth, our approach achieves extension by stretching folded materials, thereby substantially reducing growth pressure and enabling sensors and actuators to remain consistently at the tip without additional hardware. Experimental validations in narrow conduits and maze environments demonstrate the effectiveness of the proposed robots. This study presents a novel and practical approach for deploying small-scale soft growing robots in constrained and unstructured environments.