Zheng Xiaodong, Feng Shizhe, Tsang Chi Shing, Thi Quoc Huy, Han Wei, Wong Lok Wing, Liu Haijun, Lee Chun-Sing, Lau Shu Ping, Ly Thuc Hue, Xu Zhiping, Zhao Jiong
Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China.
Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology, School of Materials Science and Engineering, Hebei University of Technology, Tianjin, China.
Nat Mater. 2025 Apr 1. doi: 10.1038/s41563-025-02193-y.
Material fractures are typically irreversible, marking a one-time event leading to failure. Great efforts have been made to enhance both strength and fracture toughness of bulk materials for engineering applications, such as by introducing self-recovery and secondary breaking behaviours. In low-dimensional structures, two-dimensional materials often exhibit exceptional strength but accompanied by extreme brittleness. Here we discover that the toughness of two-dimensional materials can be enhanced without sacrificing strength-by simply twisting the layers. Through in situ scanning transmission electron microscopy, supported by nanoindentation and theoretical analysis, we reveal that twisted bilayer structures enable sequential fracture events: initial cracks heal to form stable grain boundaries, which then shield subsequent fracture tips from stress concentration. This process consumes additional energy compared with conventional fracture, with toughness enhancement tunable through twist angle adjustment. The intrinsic toughening mechanism via twisting, along with the emerging electronic properties of twistronics that are currently attracting substantial attention, presents an exciting opportunity for future devices.
材料断裂通常是不可逆的，标志着导致失效的一次性事件。人们已经做出了巨大努力来提高用于工程应用的块状材料的强度和断裂韧性，例如通过引入自修复和二次断裂行为。在低维结构中，二维材料通常表现出非凡的强度，但伴随着极高的脆性。在这里，我们发现二维材料的韧性可以在不牺牲强度的情况下得到增强——只需扭转这些层即可。通过原位扫描透射电子显微镜，并辅以纳米压痕和理论分析，我们揭示了扭曲的双层结构能够实现连续的断裂事件：初始裂纹愈合形成稳定的晶界，然后这些晶界会保护后续的断裂尖端免受应力集中的影响。与传统断裂相比，这个过程消耗了额外的能量，通过调整扭转角度可以调节韧性增强效果。通过扭转实现的固有增韧机制，以及目前正吸引大量关注的新兴的扭曲电子学的电子特性，为未来的器件提供了一个令人兴奋的机会。
