Abstract
Elephant trunks can rapidly vary their stiffness over a broad range, seamlessly switching between soft states for dexterous operation and rigid states for load-bearing tasks. Despite extensive efforts to mimic this stiffness variability using various approaches, such as jamming structures and phase-change materials, existing bionic robots are limited to narrow tunable stiffness ranges and/or slow switching frequencies. In this work, we present a bionic robotic trunk with a cable-driven tensegrity skeleton, leveraging synergistic and antagonistic muscle-mimicking mechanisms to achieve dynamic stiffness regulation. Through coordinated contraction of motor-actuated cables (i.e., antagonistic action), the robotic trunk achieves a stiffness range of 23.94 to 542.47 N/m and a switching frequency of 1.06 Hz, matching the adaptability of elephant trunks. This rapid and large-scale stiffness variation enables dexterous navigation in unstructured environments and powerful manipulation of heavy objects. Incorporated into an electric wheelchair with the human-machine interface, the robotic trunk assists a post-stroke individual with daily activities, such as opening cabinet doors, retrieving milk from refrigerators, and watering flowers. This work advances bio-inspired robotics and highlights the potential of stiffness-tunable robotic trunks in assistive applications.
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Data availability
The authors declare that the main data supporting the findings of this study are available within the article and Supplementary Information files. All the relevant data is available at https://github.com/DUT-Jay/Data-Scource_BRT.git.
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Acknowledgements
This work is supported by Natural Science Foundation of Liaoning Province Program (No. 2024JH3/50100003 and No. 2025080026-JH3/101), China Postdoctoral Science Foundation (2025M781273), and Postdoctoral Fellowship Program of CPSF (No. GZC20240192).
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Conceptualization: J.Z., X.J., and H.P. Methodology: J.Z., C.Y., H.Y., T.Z., and H.P. Investigation: J.Z., C.Y., P.M., C.H., and X.W. Visualization: J.Z., C.Y., K.L., X.J., and H.P. Funding acquisition: J.Z. and H.P. Supervision: X.J. and H.P. Writing-original draft: J.Z., C.Y., and X.J. Writing—review and editing: J.Z., X.J., and H.P.
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Zhang, J., Yang, C., Yang, H. et al. A bionic robotic trunk with tensegrity-enabled elephant-comparable stiffness variability for assisted daily living. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70380-9
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DOI: https://doi.org/10.1038/s41467-026-70380-9
