Abstract
The emergence of liquid metal (LM) emulsion as a soft multifunctional filler brings a new opportunity for fabricating hydrogel-based strain sensors with multifunctional properties. However, the extremely large surface tension and high density of LMs inhibit emulsification. Herein, we demonstrated a strategy for stabilizing LM emulsions using cationic cellulose nanofibers (CCNFs) to encapsulate LM droplets through strong electrostatic attraction with LM. By inducing acrylic acid (AA) polymerization in the presence of a CCNF-stabilized LM emulsion, a conductive hydrogel was prepared with the formation of reversible hydrogen bonds, ionic coordination, and electrostatic interactions among CCNFs, LM droplets, and poly(acrylic acid) (PAA). The hydrogel obtained, named the CCNF-LM-PAA hydrogel, shows good conductivity (1.54 S m−1), remarkable tensile strength and elongation at break, self-adhesiveness, and quick self-healing capability. As a strain-sensing material, the CCNF-LM-PAA hydrogel exhibits a very high sensing sensitivity (gauge factor = 16.2), a low strain detection limit (less than 1%), a short response/recovery time (107/91 ms), and good durability (300 cycles). These results enable the CCNF-LM-PAA hydrogel-based strain sensor to be an excellent wearable device for monitoring various human activities. Therefore, introducing additional electrostatic interactions by using CCNFs to stabilize LM emulsions provides a practical way to enhance the strain-sensing performance of LM emulsion-based hydrogels for assembling self-attached wearable devices.
摘要
作为一种多功能软填料, 液态金属(LM)乳液为制备基于导电水 凝胶的多功能应变传感器带来了新机遇. 然而, 界面张力和密度巨大的 LM难以以稳定乳液的形式存在. 本文中, 我们展示了一种利用阳离子 纤维素纳米纤维(CCNFs)包覆LM液滴来稳定LM乳液的策略. 通过将 CCNF稳定的LM乳液与丙烯酸(AA)混合并引发其原位聚合, 以及在聚 丙烯酸(PAA)、LM液滴和CCNF之间形成可逆的氢键、离子配位键和 静电交联, 制备了一种导电水凝胶CCNF-LM-PAA. 得益于PAA与 CCNF之间形成的可逆氢键、离子配位键和静电结合作用, CCNF-LMPAA 水凝胶具有良好的导电性(1.54 S m−1)、较高的拉伸强度和断裂伸 长率、粘附性和快速自愈合能力. CCNF-LM-PAA水凝胶作为应变传 感材料, 具有超高应变灵敏度(应变系数高达16.2)、低应变检测极限 (˂1%)、短响应/恢复时间(107/91 ms)和良好的耐用性(300次循环). 这 些性能使得基于CCNF-LM-PAA水凝胶的应变传感器能够作为可穿戴 电子器件用于监测各种人体活动. 因此, 利用CCNF稳定LM乳液引入静 电结合作用, 为提高基于LM乳液水凝胶的可穿戴电子器件的应变传感 性能提供了一种实用的方法.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (52172147 and 22006082), the Natural Science Foundation of Shandong Province (ZR2021MC034, ZR2021MB035, and ZR2020MB128), and Shandong Province Key Research and Development Program (2021ZDSYS18).
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Wu S and Wang B carried out the experiments and collected the data. Wu S and Liu W conceived the idea, designed the experiments, analyzed the data and wrote the paper. Liu W supervised the project. Chen D and Ge S provided the methodology. Liu X, Wang H, Song Z, Yu D and Li G analyzed the data and prepared the figures. All authors contributed to the general discussion.
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The authors declare that they have no conflict of interest.
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Supporting data are available in the online version of this paper.
Shihao Wu received his Master’s degree from the State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, China. He received his Bachelor’s degree in bioengineering from Henan University of Science and Technology, China, in 2019. His current research interests focus on cellulose-based flexible electronic devices.
Bingyan Wang is currently a graduate student at the State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, China. She received her Bachelor’s degree in food science and engineering from Shandong University of Technology, China, in 2020. Her current research interests focus on biomaterial-based flexible electronic devices.
Wenxia Liu is currently a professor at the State Key Laboratory of Biobased Materials and Green Papermaking, Qilu University of Technology, China. She received her Bachelor’s and Master’s degrees in pulp and paper engineering from Shaanxi University of Science and Technology, China, in 1985 and 1988, respectively. She joined the Faculty of Pulp and Paper Engineering at Qilu University of Technology in 1988. In 2000, she received her doctoral degree in pulp and paper engineering from Tianjin University of Science and Technology, China. Her research interests focus on paper wet-end chemistry, nanomaterials, and paper and biomass-based flexible materials.
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Highly sensitive and self-healing conductive hydrogels fabricated from cationic cellulose nanofiber-dispersed liquid metal for strain sensors
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Wu, S., Wang, B., Chen, D. et al. Highly sensitive and self-healing conductive hydrogels fabricated from cationic cellulose nanofiber-dispersed liquid metal for strain sensors. Sci. China Mater. 66, 1923–1933 (2023). https://doi.org/10.1007/s40843-022-2328-8
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DOI: https://doi.org/10.1007/s40843-022-2328-8