Localization and length-scale doubling in disordered films on soft substrates

Wrinkling and folding are examined experimentally for three distinct types of disordered films on polydimethylsiloxane (PDMS) substrates; diblock copolymers, glassy polymers, and single-wall carbon nanotubes. All three of these systems exhibit localization and length-scale doubling at small strains, and we qualitatively account for these observations with a simple physical argument related to the width of the stress correlation function and the interaction of localization sites. Our results have relevance to wrinkling and folding in a diverse array of disordered films on soft substrates, and the insights offered here should help guide the development of theoretical models for the influence of structural disorder on thin-film wrinkling instabilities.