The origin of contraction of twisted polymer fiber muscles: whether the cause is entropic elasticity or thermal expansion

Daisuke Kimura, Toshihira Irisawa, Kentaro Takagi, Kenji Tahara, Daichi Sakurai, Haruhiko Watanabe, Wataru Takarada, Masatoshi Shioya

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


In recent years, polymer fiber actuators obtained by twisting polymer fibers have attracted much attention. These actuators actuate due to the reversible axial thermal contraction and radial thermal expansion of untwisted fibers. In this study, thermal contraction of the two polyamides, PA6 and PA610, fibers were investigated. The fiber length of both fibers changed reversibly in response to temperature change, but there was no initial load dependence on the amount of contraction. These results indicate that this thermal contraction is not due to the entropic elasticity effect seen in rubber. In addition, the thermal contraction was larger for PA610, which has a larger thermal expansion coefficient in the amorphous state. This suggests that the thermal expansion of the amorphous state was converted by its fiber structure into expansion in the diameter direction and contraction in the fiber axial direction [Kimura et al., Sens. Actuators B Chem., 2021].

Original languageEnglish
Title of host publicationElectroactive Polymer Actuators and Devices (EAPAD) XXIV
EditorsIain A. Anderson, John D. W. Madden, Herbert R. Shea
ISBN (Electronic)9781510649590
Publication statusPublished - 2022
EventElectroactive Polymer Actuators and Devices (EAPAD) XXIV 2022 - Long Beach, United States
Duration: Apr 6 2022Apr 11 2022

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceElectroactive Polymer Actuators and Devices (EAPAD) XXIV 2022
Country/TerritoryUnited States
CityLong Beach

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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