Wang Zhenwu, Lai Yu-Cheng, Chiang Ya-Tang, Scheiger Johannes Martin, Li Shuai, Dong Zheqin, Cai Qianyu, Liu Sida, Hsu Shan-Hui, Chou Chia-Ching, Levkin Pavel A
Institute of Biological and Chemical Systems-Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology(KIT), Hermann-von-Helmholtz-Platz 1, Karlsruhe 76344, Eggenstein-Leopoldshafen, Germany.
Institute of Applied Mechanics, College of Engineering, National Taiwan University, Roosevelt Road No. 1, Sec. 4, Taipei 10617, Taiwan, Republic of China.
ACS Appl Mater Interfaces. 2022 Oct 28. doi: 10.1021/acsami.2c14394.
Ionically conductive elastomers are necessary for realizing human-machine interfaces, bioelectronic applications, or durable wearable sensors. Current design strategies, however, often suffer from solvent leakage and evaporation, or from poor mechanical properties. Here, we report a strategy to fabricate ionic elastomers (IHPs) demonstrating high conductivity (0.04 S m), excellent electrochemical stability (>60,000 cycles), ultra-stretchability (up to 1400%), high toughness (7.16 MJ m), and fast self-healing properties, enabling the restoration of ionic conductivity within seconds, as well as no solvent leakage. The ionic elastomer is composed of in situ formed physically cross-linked poly(2-hydroxyethyl methacrylate) networks and poly(ethylene glycol) (PEG). The long molecular chains of PEG serve as a solvent for dissolving electrolytes, improve its long-term stability, reduce solvent leakage, and ensure the outstanding mechanical properties of the IHP. Surprisingly, the incorporation of ions into PEG simultaneously enhances the strength and toughness of the elastomer. The strengthening and toughening mechanisms were further revealed by molecular simulation. We demonstrate an application of the IHPs as (a) flexible sensors for strain or temperature sensing, (b) skin electrodes for recording electrocardiograms, and (c) a tough and sensing material for pneumatic artificial muscles. The proposed strategy is simple and easily scalable and can further inspire the design of novel ionic elastomers for ionotronics applications.
离子导电弹性体对于实现人机界面、生物电子应用或耐用的可穿戴传感器是必不可少的。然而，目前的设计策略常常存在溶剂泄漏和蒸发问题，或者机械性能较差。在此，我们报告一种制备离子弹性体（IHP）的策略，该离子弹性体具有高导电性（0.04 S m）、优异的电化学稳定性（>60,000次循环）、超拉伸性（高达1400%）、高韧性（7.16 MJ m）以及快速自愈性能，能够在数秒内恢复离子导电性，且无溶剂泄漏。该离子弹性体由原位形成的物理交联聚（甲基丙烯酸2-羟乙酯）网络和聚（乙二醇）（PEG）组成。PEG的长分子链充当溶解电解质的溶剂，提高其长期稳定性，减少溶剂泄漏，并确保IHP具有出色的机械性能。令人惊讶的是，将离子引入PEG同时增强了弹性体的强度和韧性。通过分子模拟进一步揭示了强化和增韧机制。我们展示了IHP作为（a）用于应变或温度传感的柔性传感器、（b）用于记录心电图的皮肤电极以及（c）用于气动人工肌肉的坚韧且可传感材料的应用。所提出的策略简单且易于扩展，能够进一步启发用于离子电子学应用的新型离子弹性体的设计。
