Recyclable, weldable, mechanically durable, and programmable liquid metal-elastomer composites

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2021-05, Vol.9 (17), p.1953-1965
• Main Authors: Chen, Guokang, Deng, Xiaobo, Zhu, Lifei, Handschuh-Wang, Stephan, Gan, Tiansheng, Wang, Ben, Wu, Qixing, Fang, Hui, Ren, Nailin, Zhou, Xuechang
• Format: Article
• Language: English
• Subjects: Actuators; Automation; Composite materials; Conductors; Crosslinking; Elastomers; Electronics; Fabrication; Flexible components; High temperature; Liquid metals; Manufacturing engineering; Mechanical properties; Polymers; Polyurethane; Polyurethane resins; Recyclability; Robotics; Tensile strain; Wearable technology
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta11403k

Liquid metal (LM)-based elastomers have received growing interest for a wide range of applications spanning from soft robotics to flexible electronics. However, the fabrication of multifunctional LM-based elastomers, in particular, featuring recyclability and transience while simultaneously offering excellent mechanical performance and stability, remains a challenge. Herein, we report a strategy for the fabrication of durable and recyclable multifunctional LM elastomer composites, which consist of LM droplets as functional fillers and Diels-Alder (DA) bond crosslinked polyurethane (PU) networks as the polymer matrix. The composite shows good mechanical properties and can be spatially tuned from an electrical insulator to a conductor through a so-called "mechano-training" process. The mechano-trained composite exhibits extraordinarily stable electrical performance even after 10 000 stretching-releasing cycles at 100% tensile strain. The DA bond-crosslinked network endows the composite with good self-healing properties, high freedom in (re)programming of 3D shapes, and favorable transience. Moreover, spatially thermal and photothermal heating enables the repair/welding of broken circuits or programming of intricate shapes. Besides, the composite can be swiftly destructed by dissolution at an elevated temperature while the valuable LM can be retrieved at a yield of 89%. The multifunctionality, good mechanical and electrical performance, and in particular transience render this composite an environmentally friendly material for flexible transient electronics, actuators, and wearable devices. Diels-Alder (DA) bond crosslinked polyurethane (PU) networks are utilized as a matrix to fabricate multifunctional liquid metal (LM)-elastomer composites.