Sun, Jeong-Yun Xia, Shuman Moon, Myoung-Woon Oh, Kyu Hwan Kim, Kyung-Suk 2024-01-20T15:02:24Z 2024-01-20T15:02:24Z 2021-09-05 2012-04-08 1364-5021 https://pubs.kist.re.kr/handle/201004/129339 We present the mechanics of folding surface-layer wrinkles on a soft substrate, i.e. inter-touching of neighbouring wrinkle surfaces without forming a cusp. Upon laterally compressing a stiff layer attached on a finite-elastic substrate, certain material nonlinearities trigger a number of bifurcation processes to form multi-mode wrinkle clusters. Some of these clusters eventually develop into folded wrinkles. The first bifurcation of the multi-mode wrinkles is investigated by a perturbation analysis of the surface-layer buckling on a pre-stretched neo-Hookean substrate. The post-buckling equilibrium configurations of the wrinkles are then trailed experimentally and computationally until the wrinkles are folded. The folding process is observed at various stages of wrinkling, by sectioning 20-80nm thick gold films deposited on a polydimethylsiloxane substrate at a stretch ratio of 2.1. Comparison between the experimental observation and the finite-element analysis shows that the Ogden model deformation of the substrate coupled with asymmetric bending of the film predicts the folding process closely. In contrast, if the bending stiffness of the film is symmetric or the substrate follows the neo-Hookean behaviour, then the wrinkles are hardly folded. The wrinkle folding is applicable to construction of long parallel nano/micro-channels and control of exposing functional surface areas. English ROYAL SOC COMPLIANT SUBSTRATE LARGE-DEFORMATION FILMS SKINS INSTABILITY ELASTICITY ADHESION PATTERNS POLYMER SOLIDS Folding wrinkles of a thin stiff layer on a soft substrate Article 10.1098/rspa.2011.0567 1 PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, v.468, no.2140, pp.932 - 953 PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 468 2140 932 953 scie scopus 000300820800002 2-s2.0-84859567018 Multidisciplinary Sciences Science & Technology - Other Topics Article COMPLIANT SUBSTRATE LARGE-DEFORMATION FILMS SKINS INSTABILITY ELASTICITY ADHESION PATTERNS POLYMER SOLIDS wrinkle folding nonlinear deformation bifurcation post-buckling equilibrium gold film PDMS