Growing robot design

Growing robot design and application

Growing robots (or vine robots) that achieve locomotion by extending from their tip, are inherently compliant and can safely navigate through constrained environments that prove challenging for traditional robots. However, there remain many challenges with functionalizing these robots, including integrating a working channel, creating steering mechanisms, enabling retraction, and miniaturization.

Recent relevant papers:

S. Kim and T.K. Morimoto. "Kinked Air Channel Enables Retraction of Small-scale Soft Everting Robots," In IEEE 8th International Conference on Soft Robotics (RoboSoft), 2025.

A. Giri, C. Girerd, J. Cervera-Torralba, M.T. Tolley, T.K. Morimoto. "InchIGRAB: An Inchworm-Inspired Guided Retraction and Bending Device for Vine Robots during Colonoscopy". IEEE/ASME Transactions on Mechatronics (2025).

J. Davy, N. Greenidge, S. Kim, L.J. Tinsley, P. Lloyd, J.H. Chandler, R.A. Harris, T.K. Morimoto, and P. Valdastri. "Vine Robots with Magnetic Skin for Surgical Navigations." IEEE Robotics and Automation Letters (2024).

C. Girerd, A. Alvarez, E.W. Hawkes, and T.K. Morimoto. "Material Scrunching Enables Working Channels in Miniaturized Vine-Inspired Robots." IEEE Transactions on Robotics, 2024.

Retraction of small-scale everting robots

Retraction of soft everting robots via material inversion enables minimal interaction between the robot and the environment, as well as repeated growth and retraction for navigating through complex paths. However, existing retraction strategies are limited to larger-scale robots and often require integration of rigid components. In this work, we present a retraction mechanism for millimeter-scale, soft everting robots enabled by a kinked air channel. The flat air channel is attached to the robot body and kinked at the tip. This kink blocks the air flowing through the channel, allowing the pressure to effectively apply a retraction force at the tip for buckling-free retraction. We developed and validated a model by characterizing the robot at various scales and studying the effectiveness of the kinked air channel for retraction. We demonstrated the robot's retraction capability in several challenging environments, highlighting the benefits of the small size and softness of the retraction mechanism.

Miniaturization of growing robots via material scrunching

A key requirement for many applications of these robots is a working channel—a hollow tube through the core of the robot for passing tools, sensors, fluids, etc. While working channels have been proposed in a few vine robots, it remains an open challenge to create miniaturized vine robots (diameter <1 cm) with working channels that enable continuous access through the core. We analyze the growth models of current vine robot designs and show that the working channel greatly increases required pressure to grow at small scales due to internal friction. Based on this insight, we propose the concept of storing scrunched material at the tip of the vine robot to circumvent this frictional force. We validate our models and demonstrate this concept via prototypes down to diameter of 2.3 mm. Overall, this work enables the creation of miniaturized vine robots with working channels, which significantly enhances their practicality and potential for impact in applications such as minimally invasive surgery.

InchIGRAB: An Inchworm-Inspired Guided Retraction and Bending Device

We introduce a novel soft robotic system for colonoscopy that consists of an inchworm-inspired device --- the InchIGRAB --- nested within a vine robot. The InchIGRAB is designed to enable steering of the vine robot along curved paths, as well as to enable controlled retraction of the vine robot after it reaches its target.

Growing robots with magnetic skin

We considered the external manipulation of growing robots through the utilization of magnetically active materials embedded within the vine robot’s skin. This results in a completely flexible, steerable, growing structure that can be actuated via the application of external magnetic fields and field gradients. We explore the principles of magnetically-guided vine robots and provide empirical evidence highlighting the efficacy of our proposed magnetic steering methodology. Due to the inverted internal structure, careful design of the magnetization direction of the robot has to be considered. We propose an orthogonal magnetization strategy that successfully preserves a net positive magnetization. We demonstrate the ability of our robots to navigate complex environments and steer around large obstacles in a shear free manner via the simultaneous control of both the magnetic field and the growing pressure.

VINE Catheter

We are developing a novel tip-extending catheter that grows through vessels in a manner analogous to how plants grow, termed Vascular Internal Navigation by Extension (VINE). The VINE catheter efficiently navigates tight turns and extreme angles due to its low bending stiffness and lack of sliding friction with vessel walls. Further, the soft, growing construction of VINE catheters results in reduced force on the leading edge, potentially reducing the risk of arterial injury compared to standard push-catheters.

Recent relevant papers:

M. Li, R. Obregon, J.J. Heit, A. Norbash, E.W. Hawkes, T.K. Morimoto. "VINE Catheter for Endovascular Surgery." IEEE Transactions on Medical Robotics and Bionics 3.2 (2021): 384-391.

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