Soft Growing Robots

Soft robotics is a specialized subfield of robotics focused on constructing robots using soft and compliant materials, akin to those found in living organisms. In the IRiS Lab, we have been actively researching eversion-based soft growing robots, inspired by the tip growth mechanisms of vines and plant roots. Unlike conventional robots that move via surface contact, soft growing robots achieve locomotion by continuously everting at the tip. Powered by air or water pressure, this tip extension enables navigation through highly constrained environments. These robots offer significant advantages for exploration: they can access gaps narrower than their own diameter, traverse slippery or adhesive surfaces, and achieve vertical movement due to their lightweight structure. Such features make them exceptionally well-suited for navigating complex and unstructured environments.

Our research primarily focuses on the hardware development of these robots. In particular, we are investigating design strategies to maintain a functional and accessible inner channel for tool deployment and sensor insertion, enabling multifunctional task execution during growth. We are also developing reliable retraction mechanisms for repeatability and exploring alternative materials to improve performance, durability, and task-specific adaptability. These efforts support a wide range of potential applications, including medical procedures, industrial inspections, search and rescue operations, and subsurface excavation.

Application

Vine Colonoscopy (Soft Growing Endoscope)

Associated Papers

  • Kim, N. G., Park, S., Seo, D., Lee, S., Yoon, H., Kim, J., & Ryu, J. H. (2026). A soft growing robotic endoscope for painless and strain-free insertion. Soft Robotics, 13(1), 5-18.

Search & Rescue

Associated Papers

  • S. -G. Jeong et al., “A Tip Mount for Transporting Sensors and Tools using Soft Growing Robots,” 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
  • Lee, S., Kim, N. G., Seo, D., Park, S., & Ryu, J. H. (2025, May). Helical Structured Soft Growing Robot for Hazardous Gas Suction in Inaccessible Environments. In 2025 IEEE International Conference on Robotics and Automation (ICRA) (pp. 12907-12913). IEEE.

ETC

Associated Papers

  • Han, G., Seo, D., Ryu, JH. et al. RootBot: root-inspired soft-growing robot for high-curvature directional excavation. Acta Geotech. 19, 1365–1377 (2024).
  • Kim, N. G., Heap, W. E., Qin, Y., Yao, E. B., Ryu, J. H., & Okamura, A. M. (2025). Self-Wearing Adaptive Garments via Soft Robotic Unfurling. IEEE Robotics and Automation Letters, 11(1), 802-809.
  • Park, S., Kim, N. G., Seo, D., Lee, S., & Ryu, J. H. Bistable Steering Mechanism for Enhanced Control in Soft Toroidal Robots. Soft Robotics, 21695172261438632.

Fundamental Problem Solving

Steering & Shape Locking

To navigate highly curved or cluttered environments, soft growing robots must go beyond passive deformation and actively steer their growth direction. Our lab focuses on developing steering strategies that preserve the robot’s soft and extensible body while enabling precise and repeatable directional control. One approach involves active tip bending, where we design a compact steering module that integrates a rolling contact joint and a twisted string actuator (TSA) at the robot’s tip. This mechanism enables high-curvature turns by locally bending the tip, allowing the robot to make consecutive directional changes without affecting the rest of the body—a crucial feature for navigating tight or branched spaces. Another approach explores whole-body steering by using external magnetic fields. By embedding a permanent magnet near the robot’s tip, we can steer the robot by inducing smooth body-wide curvature from the outside. This method minimizes internal actuation complexity and is particularly effective in delicate or unstructured environments where physical contact should be avoided. In addition, we have investigated how material-level properties can be exploited to enhance steering performance. Specifically, we utilize hyperelastic materials with shape-locking characteristics to achieve stable, high-curvature configurations without requiring external constraints or additional hardware. This approach enables wrinkle-free curve formation, reduced tail tension, and improved steerability while maintaining the robot’s soft and compliant nature.

Associated Papers

  • D. -G. Lee, N. G. Kim and J. -H. Ryu, “High-Curvature Consecutive Tip Steering of a Soft Growing Robot for Improved Target Reachability,” 2023 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).
  • Nam Gyun Kim, Nikita J. Greenidge, Joshua Davy, Shinwoo Park, James H. Chandler, Jee-Hwan Ryu, and Pietro Valdastri, “External Steering of Vine Robots via Magnetic Actuation” Soft Robotics (2025)
  • Kim, Nam Gyun, and Jee-Hwan Ryu. “A soft growing robot using hyperelastic material.” Advanced Intelligent Systems 5.2 (2023)

Tip Mount & Inner Channel

Ensuring a stable and accessible inner channel is essential for soft growing robots to deploy tools, transmit sensory data, and perform complex tasks during growth. However, the eversion-based locomotion of these robots makes it challenging to maintain such a channel without disrupting their soft, compliant structure. One approach we pursue is a structural stabilization method using subvines—small inflatable tubes embedded within the robot body that grow simultaneously with the main membrane. These subvines preserve the geometry of the inner channel under variable pressure conditions, enabling continuous access for tools and components without interference from the actuation pressure. Another approach focuses on a feeding-stacking mechanism based on origami-inspired designs, which allows internal components—such as cameras or manipulators—to be independently advanced and positioned at the tip. This design decouples the internal payload movement from the robot’s body growth, enabling precise control of tool positioning even in cluttered or tortuous environments.

Associated Papers

  • Seo, Dongoh, Nam Gyun Kim, and Jee-Hwan Ryu. “Inflatable-Structure-Based Working-Channel Securing Mechanism for Soft Growing Robots.” IEEE Robotics and Automation Letters (2024).
  • J. -h. Kim, J. Jang, S. -m. Lee, S. -G. Jeong, Y. -J. Kim and J. -H. Ryu, “Origami-inspired New Material Feeding Mechanism for Soft Growing Robots to Keep the Camera Stay at the Tip by Securing its Path.” IEEE Robotics and Automation Letters (2021).
  • S. -G. Jeong et al., “A Tip Mount for Transporting Sensors and Tools using Soft Growing Robots,” 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
  • Lee, S., Kim, N. G., Park, S., Lee, D. Y., & Ryu, J. H. (2026). Origami-Based Inner Channel Securing Mechanism for Soft Growing Robots. IEEE Robotics and Automation Letters, 11(5), 5970-5977.

Retraction

Retraction is essential for the practical deployment and reuse of soft growing robots, yet conventional approaches often rely on rigid components or complex actuation systems that undermine the robot’s soft, compliant nature. Our lab addresses this challenge by developing fully soft retraction mechanisms that enable fast and reliable reversal of robot growth—without additional hardware at the tip or along the body. Leveraging the robot’s existing pneumatic infrastructure, our method allows the robot to retract swiftly while avoiding buckling, preserving the integrity of both the outer membrane and the internal channel. Unlike conventional methods that require heavy driving fluids or mechanical constraints, our approach maintains compatibility with mounted sensors, steering modules, and other application-specific features. By ensuring minimal hardware complexity and high operational reliability, our retraction strategy supports real-world deployment scenarios where reversibility, compactness, and speed are essential—from pipeline exploration to medical retrieval tasks.

Associated Papers

  • N. G. Kim, D. Seo, S. Park and J. -H. Ryu, “Self-Retractable Soft Growing Robots for Reliable and Fast Retraction While Preserving Their Inherent Advantages.” IEEE Robotics and Automation Letters (2024).