title: Universality of periodicity as revealed from interlayer-mediated cracks.
abstract: A crack and its propagation is a challenging multiscale materials phenomenon of broad interest, from nanoscience to exogeology. Particularly in fracture mechanics, periodicities are of high scientific interest. However, a full understanding of this phenomenon across various physical scales is lacking. Here, we demonstrate periodic interlayer-mediated thin film crack propagation and discuss the governing conditions resulting in their periodicity as being universal. We show strong confinement of thin film cracks and arbitrary steering of their propagation by inserting a predefined thin interlayer, composed of either a polymer, metal, or even atomically thin graphene, between the substrate and the brittle thin film. The thin interlayer-mediated controllability arises from local modification of the effective mechanical properties of the crack medium. Numerical calculations incorporating basic fracture mechanics principles well model our experimental results. We believe that previous studies of periodic cracks in SiN films, self-de-bonding sol-gel films, and even drying colloidal films, along with this study, share the same physical origins but with differing physical boundary conditions. This finding provides a simple analogy for various periodic crack systems that exist in nature, not only for thin film cracks but also for cracks ranging in scale.
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Myung Rae
authors.initials: MR
authors.lastname: Cho
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Jong Hyun
authors.initials: JH
authors.lastname: Jung
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Min Key
authors.initials: MK
authors.lastname: Seo
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Sung Un
authors.initials: SU
authors.lastname: Cho
authors.affiliation: Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: Young Duck
authors.initials: YD
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.|Institute of Applied Physics (IAP), Seoul National University, Seoul, 08826, South Korea.
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747, South Korea.
authors.forename: Yong Seung
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Pilkwang
authors.initials: P
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: James
authors.initials: J
authors.lastname: Hone
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
authors.forename: Jisoon
authors.initials: J
authors.lastname: Ihm
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.|Institute of Applied Physics (IAP), Seoul National University, Seoul, 08826, South Korea.
authors.forename: Yun Daniel
authors.initials: YD
authors.lastname: Park