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A Pneumatic Bending Actuator System Inspired by the Avian Tendon Locking Mechanism

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Part of the Lecture Notes in Computer Science book series (LNAI,volume 14158)


The tendon locking mechanism (TLM) in the avian foot allows birds to perch on a tree or grasp prey for long periods of time with low energy input. In this study, we present a soft robotic pneumatic bending actuator system inspired by the TLM, consisting of three flexible main components. The first component is an index finger-sized soft robotic pneumatic bending actuator (SPA) with a 90° pre-curved shape that stretches in the opposite direction to classical designs when pressurized. The other two components are a tendon that interconnects the SPA’s air chambers and a soft pneumatic tendon sheath (SPTS) that can lock the movement of the tendon. The SPTS requires 160 kPa of pressurized air to release the tendon and locks it through an elastic ligament-based design when actuation stops. The bending actuator can thus be fully stretched with as little as 60 kPa, while generating up to 4.61 ± 0.38 N of block force. This design allows the construction of grippers that can be operated at low air pressure and do not require actuation while gripping and holding objects.


  • Soft robotics
  • Soft machines
  • Biomimetics
  • Additive manufacturing
  • FDM printing

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Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2193/1 – 390951807.

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Correspondence to Peter Kappel .

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Kappel, P., Kürner, L., Speck, T., Tauber, F. (2023). A Pneumatic Bending Actuator System Inspired by the Avian Tendon Locking Mechanism. In: Meder, F., Hunt, A., Margheri, L., Mura, A., Mazzolai, B. (eds) Biomimetic and Biohybrid Systems. Living Machines 2023. Lecture Notes in Computer Science(), vol 14158. Springer, Cham.

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  • Print ISBN: 978-3-031-39503-1

  • Online ISBN: 978-3-031-39504-8

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