title: Indentation of ultrathin elastic films and the emergence of asymptotic isometry.
abstract: We study the indentation of a thin elastic film floating at the surface of a liquid. We focus on the onset of radial wrinkles at a threshold indentation depth and the evolution of the wrinkle pattern as indentation progresses far beyond this threshold. Comparison between experiments on thin polymer films and theoretical calculations shows that the system very quickly reaches the far from threshold regime, in which wrinkles lead to the relaxation of azimuthal compression. Furthermore, when the indentation depth is sufficiently large that the wrinkles cover most of the film, we recognize a novel mechanical response in which the work of indentation is transmitted almost solely to the liquid, rather than to the floating film. We attribute this unique response to a nontrivial isometry attained by the deformed film, and we discuss the scaling laws and the relevance of similar isometries to other systems in which a confined sheet is subjected to weak tensile loads.
authors.affiliation: Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.
authors.forename: Dominic
authors.initials: D
authors.lastname: Vella
authors.affiliation: Physics Department, University of Massachusetts, Amherst, Massachusetts 01003, USA and Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Jiangshui
authors.initials: J
authors.lastname: Huang
authors.affiliation: Physics Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Narayanan
authors.initials: N
authors.lastname: Menon
authors.affiliation: Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Russell
authors.affiliation: Physics Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Benny
authors.initials: B
authors.lastname: Davidovitch