@article{9a692e9ad9044e82895f3d649f091f74,
title = "Electrically controllable twisted-coiled artificial muscle actuators using surface-modified polyester fibers",
abstract = "As a new class of thermally activated actuators based on polymeric fibers, we investigated polyethylene terephthalate (PET) yarns for the development of a twisted-coiled polymer fiber actuator (TCA). The PET yarn TCA exhibited the maximum linear actuation up to 8.9% by external heating at above the glass transition temperature, 160 anddeg;C-180 anddeg;C. The payload of the actuator was successfully correlated with the preload and training-load conditions by an empirical equation. Furthermore, the PET-based TCA was electrically driven by Joule heating after the PET surface was metallization with silver. For the fast and precise control of PET yarn TCA, electroless silver plating was conducted to form electrical conductive layers on the PET fiber surface. The silver plated PET-based TCA was tested by Joule heating and the tensile actuation was increased up to 12.1% (6 V) due to the enhanced surface hardness and slippage of PET fibers. Overall, silver plating of the polymeric yarn provided a fast actuation speed and enhanced actuation performance of the TCA actuator by Joule heating, providing a great potential for being used in artificial muscle for biomimetic machines including robots, industrial actuators and powered exoskeletons.",
keywords = "Joule heating, artificial muscle, electroless silver plating, twisted-coiled fiber actuator (TCA)",
author = "Jungwoo Park and Yoo, {Ji Wang} and Seo, {Hee Won} and Youngkwan Lee and Jonghwan Suhr and Hyungpil Moon and Koo, {Ja Choon} and Choi, {Hyouk Ryeol} and Robert Hunt and Kim, {Kwang Jin} and Kim, {Soo Hyun} and Nam, {Jae Do}",
note = "Funding Information: No difference of depolarization was found between the ceramic and single-crystal YAG for the same Nd{"} concentration. Thermal birefringence in an isotropic material is always given by' even if the beam propagates along any directions, where n, and nt are the radial and the azimuthal refractive indices in a plane perpendicular to the direction of beam propagation, respectively, n0is the initial refractive index, pM and pu are photoelastic coefficients, and e, and e« are strain tensors. Although the symmetry of crystalline YAG is not isotropic but cubic, this result indicates that the thermal birefringence induced in YAG crystal is nearly the same in isotropic materials because the ceramics consist of a lot ofYAG-crystal grains (several tens of microns in diameter) with various directions. Moreover, it was also found that the depolarization became larger in samples with higher Nd{"} concentration even if the same pump power was absorbed. One reason for that is the difference of thermal distribution in the samples. In the case of end pumping, the sample with higher Nd5* concentration localizes the heat near its surface because it has larger absorption coefficient or shorter absorption depth. The localized heat lowers the thermal conductivity, making the temperature even higher and the induced strains larger, vfhkh results in larger thermal birefringence. Another reason is the difference of thermal loading. For a highly Nd{"}-doped sample, in which the interaction between Nd{"} ions is significant, the amount of nonradiative relaxation increases and radiative quantum efficiency gets smaller. Under the condition of no laser extraction, the smaller quantum efficiency causes larger thermal loading, that is, more heat generation in the sample even at the same absorbed power, and this induces larger thermal birefringence. When lasing occurs, on the other hand, thermal birefringence is expected to be greatly reduced because the thermal loading is independent of radiative quantum efficiency. This means that evi operation is preferable for highly Nd{"} -doped ceramics, while Q-switching is not. It is necessary to use Nd:YAG ceramics which have optimal Nd{"} concentrations arid optimal lengths for various applications. This work was partially supported by the Grant-in-Aid for Scientific Research #12792003, from The Ministry of Education, Science, Sports and Culture of lapan. Publisher Copyright: {\textcopyright} 2017 IOP Publishing Ltd.",
year = "2017",
month = feb,
day = "17",
doi = "10.1088/1361-665X/aa5323",
language = "English",
volume = "26",
journal = "Smart Materials and Structures",
issn = "0964-1726",
publisher = "IOP Publishing Ltd.",
number = "3",
}