Faculty, Staff and Student Publications

Language

English

Publication Date

10-8-2024

Journal

Proceedings of the National Academy of Sciences of the United States of America

DOI

10.1073/pnas.2412288121

PMID

39348536

PMCID

PMC11474079

PubMedCentral® Posted Date

9-30-2024

PubMedCentral® Full Text Version

Post-print

Abstract

Biomimetic actuation technologies with high muscle strokes, cycle rates, and work capacities are necessary for robotic systems. We present a muscle type that operates based on changes in muscle stiffness caused by volume expansion. This muscle is created by coiling a mechanically strong braid, in which an elastomer hollow tube is adhesively attached inside. We show that the muscle reversibly contracts by 47.3% when driven by an oscillating input air pressure of 120 kilopascals at 10 Hz. It generates a maximum power density of 3.0 W/g and demonstrates a mechanical contractile efficiency of 74%. The muscle's low-pressure operation allowed for portable, thermal pneumatical actuation. Moreover, the muscle demonstrated bipolar actuation, wherein internal pressure leads to muscle length expansion if the initial muscle length is compressed and contraction if the muscle is not compressed. Modeling indicates that muscle expansion significantly alters its stiffness, which causes muscle actuation. We demonstrate the utility of BCMs for fast running and climbing robots.

Keywords

Robotics, Muscle Contraction, Biomimetics, Muscle, Skeletal, Biomechanical Phenomena, Humans, Muscles, artificial muscle, thermal-pneumatic, variable stiffness, soft robotics

Published Open-Access

yes

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