Curling behavior of free-standing nanofilms driven by surface stress: core–shell model Jiangang Li, Xiao Lei, Jianhua Ding, Zhixiang Gao and Hua Wang Eur. Phys. J. Appl. Phys., 97 (2022) 85 Published online: 02 December 2022 DOI: 10.1051/epjap/2022220185