Abstract
Electrothermal sheath-run artificial muscles hold great promise for various applications. Their sheath expands and softens when subjected to Joule heat generated by high currents, effectively releasing the stored torsional energy within the core fiber. This phenomenon significantly enhances actuation performance. In this study, an artificial muscle composed of pre-twisted carbon nanotube (CNT) fiber encased in polydimethylsiloxane (PDMS) sheath was prepared. Under a 50-mA current at a frequency of 0.25 Hz, it demonstrated a 13.28% contraction stroke and 9.82 MPa contraction stress, with a power density of 3.8 W g−1. Notably, thanks to its non-coiled structure, CNT fiber@PDMS can operate at speeds of up to 42% s−1, and be applied to switches and biomimetic arms. Interestingly, we observed improved actuation performance even with relatively weak currents that were insufficient to induce the expansion and softening of the PDMS sheath typically required for actuation. To explain this phenomenon, a mechanism involving the densification of the CNT fiber by the PDMS sheath was proposed. When electrified, the CNT fiber initiates Ampere attraction forces among its internal CNTs, generating actuation. Simultaneously, the curing process of the PDMS sheath induces radial compressive stresses, reducing the spacing between CNTs and thereby increasing the Ampere attraction force. We substantiated this mechanism through investigations into actuation behavior at different temperatures, internal microstructure, and the mechanical and electrical properties of the CNT fiber@PDMS, ultimately providing a comprehensive analysis of energy changes throughout the actuation process.
摘要
电热驱动的鞘状人工肌肉已经展示出广阔的应用前景. 当受到 高电流产生的焦耳热影响时, 它们的鞘层会膨胀和软化, 有效地释放芯 部纤维内储存的扭转能量, 这种现象显著地提高了驱动性能. 本工作制 备了一种包裹在聚二甲基硅氧烷(PDMS)鞘层中的预捻碳纳米管(CNT) 人工肌肉纤维. 施加频率为0.25 Hz的50 mA电流, 其可以产生13.28%的 收缩变形和9.82 MPa的收缩应力, 功率密度为3.8 W g−1. 得益于非螺旋 结构, CNT纤维@PDMS的运行速率可达42% s−1, 我们据此开发了快速 运行的开关和仿生臂. 有趣的是, 我们观察到即使在较弱的电流不足以 诱导驱动所需的PDMS鞘层膨胀和软化的情况下, CNT纤维@PDMS的 驱动性能也有所改善. 为了解释这一现象, 我们提出了一种鞘层致密化 机制. 当电流通入CNT纤维时, 其内部CNTs间产生的安培吸引力也会 引发驱动, PDMS鞘层在固化过程中产生沿CNT纤维径向分布的收缩应 力, 会使CNTs间距减小, 从而提升安培吸引力. 我们通过检测CNT纤维@PDMS在不同温度下的驱动行为、内部微观结构、力学和电学性能 的变化证实了这种致密化机制的存在, 并分析了整个驱动过程中能量的变化.
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Acknowledgements
This work was supported by the National Key Research and Development Program of China (2020YFB1312900) and the National Natural Science Foundation of China (21975281).
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Author contributions Zhao Z conducted the methodology, preparation, testing, and original draft writing. Zhu S focused on the mechanism investigation. Yang G handled experimental details. Dong X was involved in supervision, conceptualization, and writing and editing. Di J contributed to research ideas and revision of the manuscript. Qi M performed validation. Huang H conducted oxygen plasma modification. All authors participated in the article, and gave approval to the submitted version.
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Supplementary information Experimental details and supporting data are available in the online version of the paper.
Zenghui Zhao obtained his Master’s degree in materials science from Dalian University of Technology in 2022 and continued to pursue a doctoral degree under the guidance of Professor Xufeng Dong. His research interest is the application of carbon nanotube fibers in the field of artificial muscles.
Xufeng Dong is a professor at the School of Materials Science and Engineering, Dalian University of Technology. He obtained his Bachelor’s, Master’s and doctor’s degrees from Harbin Institute of Technology in 2003, 2005, and 2009, respectively. His research interests mainly focus on smart materials and biomedical materials.
Jiangtao Di is currently a professor at Suzhou Institute of Nanotechnology, Chinese Academy of Sciences. He graduated from Jiangsu University of Science and Technology with a Bachelor’s degree in applied chemistry in 2008 and from the University of the Chinese Academy of Sciences with a Doctor’s degree in physical chemistry in 2013. From 2013 to 2016, he served as an associate professor at the University of Texas at Dallas, and in 2016, he joined Suzhou Institute of Nanotechnology, Chinese Academy of Sciences. His research interests focus on the physical chemistry of smart materials and highly conductive materials.
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Zhao, Z., Zhu, S., Yang, G. et al. Enhancement actuation mechanism for the sheath-run artificial muscle fiber under weak current. Sci. China Mater. 66, 4794–4802 (2023). https://doi.org/10.1007/s40843-023-2618-5
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DOI: https://doi.org/10.1007/s40843-023-2618-5