An Implantable Variable Length Actuator for Modulating in Vivo Musculo-Tendon Force in a Bipedal Animal Model

Sean Thomas, Ravin Joshi, Bo Cheng, Huanyu Cheng, Michael C. Aynardi, Gregory S. Sawicki, Jonas Rubenson

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Mobility, a critical factor in quality of life, is often rehabilitated using simplistic solutions, such as walkers. Exoskeletons (wearable robotics) offer a more sophisticated rehabilitation approach. However, non-adherence to externally worn mobility aids limits their efficacy. Here, we present the concept of a fully implantable assistive limb actuator that overcomes non-adherence constraints, and which can provide high-precision assistive force. In a bipedal animal model (fowl), we have developed a variable length isometric actuator (measuring φ9 x 30 mm) that is able to be directly implanted within the leg via a bone anchor and tendon fixation, replacing the lateral gastrocnemius muscle belly. The actuator is able to generate isometric force similar to the in vivo force of the native muscle, designed to generate assistive torque at the ankle and reduce muscular demand at no additional energy cost. The device has a stroke of 10 mm that operates up to 770 mm/s (77 stroke lengths/s), capable of acting as a clutch (disengaging when needed) and with a tunable slack length to modulate the timing and level of assistive force during gait. Surgical techniques to attach the actuator to the biological system, the Achilles tendon and tibia, have been established and validated using survival surgeries and cadaveric specimens.

Original languageEnglish (US)
Title of host publication2023 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2023
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781665491907
StatePublished - 2023
Event2023 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2023 - Detroit, United States
Duration: Oct 1 2023Oct 5 2023

Publication series

NameIEEE International Conference on Intelligent Robots and Systems
ISSN (Print)2153-0858
ISSN (Electronic)2153-0866


Conference2023 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2023
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Software
  • Computer Vision and Pattern Recognition
  • Computer Science Applications

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