Science in China Series E: Technological Sciences © 2008 SCIENCE IN CHINA PRESS Springer Received October 15, 2007; accepted January 15, 2008; published online September 11, 2008 doi: 10.1007/s11431-008-0118-5 † Corresponding author (email: junsun@mail.xjtu.edu.cn) Supported by the National Basic Research Program of China (Grant No. 2004CB619303), the 111 Project of China (Grant No. B06025), and the Science and Technology Key Project from Ministry of Education of China (Grant Nos. 02182, 03182) Sci China Ser E-Tech Sci | Nov. 2008 | vol. 51 | no. 11 | 1971-1979 www.scichina.com tech.scichina.com www.springerlink.com Ductility of metal thin films in flexible electronics NIU RongMei, LIU Gang, DING XiangDong & SUN Jun † State Key Laboratory for Mechanical Behavior of Materials and School of Materials Science & Engineering, Xi’an Jiaotong University, Xi’an 710049, China Flexible, large area electronics using various organic and inorganic materials are beginning to show great promise. During manufacture and service, large deforma- tion of these hybrid materials will pose significant challenges in terms of high performance and reliability. A deep understanding of the ductility or flexibility of macroelectronics becomes one of the major issues that must be addressed ur- gently. This paper describes the current level of understanding on the thin-film ductility, both free-standing and substrate-supported, and relevant influencing factors. thin films, deformation, flexible electronics In recent years, remarkable progress on enlarging system scale has given rise to a nascent field known as macroelectronics [1,2] . The most visible example of macroelectronics at present is flat-panel displays, which have been rapidly replacing cathode-ray tubes as the monitors of choice for computers and televisions since 2000. The commercial success of flat-panel display opens an era of large area electronics, and other emerging applications, such as rollable display [3] , printable thin-film solar cell [4] and electronic skin [5] , demonstrate further desirable attributes for macro- electronic systems, including flexibility, portability and low-cost. Accordingly, a growing trend is to fabricate macroelectronic products directly on flexible substrates, such as polymers. The flat-panel displays made on thin polymer substrates are rugged, lightweight and can be rolled up― they will be portable. For example, the world’s first prototype of a rollable electronic reader, which can unfold to a 5-inch display and roll back into a pocket-size (100 mm×60 mm×20 mm) device. Flexible electronics have the opportunity not only to revolutionize an industry but also to create entirely new ones [1] . Notwithstanding the advances in device performance, there are traditional materials challenges in the enabling structures that must be addressed. Flexible electronics are mostly made of elec- tronic thin films (metals, dielectrics and semiconductors) on compliant substrates. For example, in