Abstract
Thermo-responsive shape memory hydrogels generally achieve shape fixation at low temperatures, and shape recovery at high temperatures. However, these hydro-gels usually suffer from poor mechanical properties. Herein, we present a unique poly(acrylic acid)/calcium acetate shape memory hydrogel with cold-induced shape recovery performances as ultrastrong artificial muscles. Since the acetate groups could form aggregate at high temperatures and thus induce the association of the hydrogel network, the hydrogel can be fixed into a temporary shape upon heating and recover to its original shape in a cold environment. Moreover, a programmable shape recovery process is realized by adjusting the shape fixing time. In addition, the unique shape memory process enables the application demonstration as bio-inspired artificial muscles with an ultrahigh work density of 45.2 kJ m−3, higher than that of biological muscles (∼8 kJ m−3).
摘要
热致响应形状记忆水凝胶通常在低温时固定临时形状, 升高温度回复至初始形状. 然而, 水凝胶高含水量的特点导致其较弱的力学性能, 限制了其广泛应用. 本文介绍了一种具有独特的冷致形状回复功能的聚丙烯酸/乙酸钙水凝胶, 由于乙酸基团在高温下形成聚集体, 进而会导致聚丙烯酸网络的疏水聚集和硬化, 因而水凝胶的临时形状可在70°C时固定, 并在20°C的低温环境回复至初始形状. 同时, 通过调控形状固定时间可以实现分步形状恢复. 这种形状记忆水凝胶可用作人工肌肉, 其做功能力高达45.2 kJ m−3, 远超过一般动物肌肉的做功能力(∼8 kJ m−3).
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (51873223 and 22075154) and the Natural Science Foundation of Zhejiang Province (LY19B040001).
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Author contributions Hua L conducted most of the experiments and drafted the manuscript; Zhao C designed the experiments and drafted the manuscript; Guan X helped with the synthesis of the hydrogel; Lu J conducted the rheology experiments; Zhang J initiated and guided the work and drafted the manuscript. All authors contributed to the discussion and preparation of the manuscript.
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Supplementary information Experimental details and supporting data are available in the online version of the paper.
Luqin Hua received her BSc degree from Ningbo University in 2020. She is now a master candidate at Ningbo University under the supervision of Prof. Chuanzhuang Zhao. Her research interest focuses on shape memory hydrogels and their applications.
Chuanzhuang Zhao received his PhD degree in polymer chemistry and physics from Nankai University in China in 2010. After postdoctoral training at the Institute of Chemistry, Chinese Academy of Sciences, he joined Ningbo University in 2013, and now he is an associate professor. His current research involves the synthetic chemistry and physical chemistry of stimuli-responsive polymers.
Jiawei Zhang received her PhD degree in polymer chemistry and physics from Nankai University in China in 2010, during which she had research training at the University of Montreal (2007–2009, Canada). After postdoctoral training at Tsinghua University, China, she joined Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences in 2013, and now she is a professor of Tiangong University. Her research interest includes smart polymeric hydrogel actuators and shape memory hydrogels.
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Hua, L., Zhao, C., Guan, X. et al. Cold-induced shape memory hydrogels for strong and programmable artificial muscles. Sci. China Mater. 65, 2274–2280 (2022). https://doi.org/10.1007/s40843-021-1971-9
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DOI: https://doi.org/10.1007/s40843-021-1971-9