Robust integrity of graphene in heavily stretched copper composites

Copper (Cu) is widely used in the electrical industry due to its excellent conductivity, but its mechanical performance often limits its application in next-generation power devices. Graphene has emerged as a promising second-phase additive to enhance the mechanical properties of Cu while maintaining high conductivity. However, a fundamental challenge remains: how does graphene behave under extreme tensile deformation, such as during wire fabrication?

A research team led by Prof. Kaihui Liu at Peking University proposes a “strain-slip” mechanism that explains how graphene maintains structural integrity when integrated into Cu matrices and subjected to stretching. Using a model system of monolayer graphene grown on single-crystal Cu foils, the team conducted systematic optical imaging, Raman spectroscopy, and Kelvin probe force microscopy during tensile testing.

Their experiments revealed that graphene deforms with the Cu substrate up to a critical strain, after which it undergoes relative slippage along the Cu surface. Despite the stretching, no significant fracture or delamination of graphene was observed. Raman vector decomposition confirmed that the actual strain within the graphene layer is much smaller than that in the Cu matrix, owing to pre-existing wrinkles and compressive strain. The calculated interfacial shear stress (∼1.8 MPa) is five orders of magnitude lower than graphene’s intrinsic strength, confirming its mechanical resilience.

Furthermore, the team fabricated meter-long Gr/Cu wires and evaluated their electrical and mechanical performance. The annealed Gr/Cu wires exhibited a remarkable conductivity of 102.2% IACS, while the unannealed Gr/Cu wires demonstrated a 12.9% increase in tensile strength compared to pure Cu wires, highlighting graphene’s dual role as both a conductor and a mechanical reinforcer.

This study provides direct experimental and theoretical evidence for a “strain-slip” protection mechanism in Gr/Cu composites. It offers a new design paradigm for integrating graphene into stretchable electronic systems and developing high-performance, durable conductive wires for power transmission, flexible electronics, and beyond.

Other contributors include Chong Zhao, Yu Wang, Wanting Sun, Qianyi Liu, Min Ding, Jijun Wang, Qingqiu Cheng, Ying Fu from Songshan Lake Materials Laboratory in Dongguan, China; Muhong Wu from Beihang University in Beijing, China and Zhibin Zhang, Menze Zhao from the School of Physics at Peking University in Beijing, China.

This work was supported by Guangdong Major Project of Basic and Applied Basic Research (2021B0301030002), the National Natural Science Foundation of China (52172035, 52025023, 52021006, 52402043 and T2188101, U24A20285), China Postdoctoral Science Foundation (2023M730103), the National Key R&D Program of China (2021YFA1400502).

About the Authors

Kaihui Liu is a Boya Distinguished Professor at Peking University and Director of the Institute of Condensed Matter and Materials Physics. His research focuses on materials physics and spectroscopic physics. In recent years, he has published as corresponding author in Science (3 papers), Nature (3 papers), Nature sub-journals (23 papers), and Physical Review Letters (3 papers). Prof. Liu has received many prestigious awards, including the National Science Fund for Distinguished Young Scholars, the XPLORER PRIZE, the First Prize of Beijing Natural Science Award and the Hu Gangfu Award of the Chinese Physical Society. His research achievements have been recognized among China’s Top 10 Scientific and Technological Advances (2020), Top 10 Semiconductor Research Advances in China (2020, 2024), and Major Scientific and Technological Achievements of the Zhongguancun Forum (2024, 2025).

Research group website: http://liugroup.pku.edu.cn/chs_home.html

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.