Wrinkling and folding of thin films by viscous stress

Abstract

We examine the buckling of a thin elastic film floating on a viscous liquid layer which is itself supported on a prestretched rubber sheet. Releasing the prestretch in the rubber induces a viscous stress in the liquid, which in turn induces a compressive stress in the elastic film, leading to buckling. Unlike many previous studies on wrinkling of floating films, the buckling process in the present study is dominated by viscous effects whereas gravitational effects are negligible. An approximate shear lag model predicts the evolution of the stress profile in the unbuckled film that depends on three parameters: the rate at which the prestretch is released, the thickness of the liquid layer, and the length of the elastic film. A linear perturbation analysis is developed to predict the wavelength of wrinkles. Numerical simulations are conducted to predict nonlinear evolution of the wrinkle wavelength and amplitude. Experiments using elastic polymer films and viscous polymer liquids show trends that are qualitatively consistent with the predictions although quantitatively, the experimentally-observed wrinkle wavelengths are longer than predicted. Although this article is focused only on small-strain wrinkling behavior, we show that application of large nominal strains (on the order of 100%) leads to sharply localized folds. Thus this approach may be useful for developing buckled features with high aspect ratio on surfaces.

Strained Epitaxy of Monolayer Transition Metal Dichalcogenides for Wrinkle Arrays

“…The periodic delamination forms the wrinkle array with a wavelength that is only dependent on the intrinsic properties of substrate and film (Young’s modulus and Poisson’s ratio). , In short, the increased strain rate leads to an increase in the instability of buckling. The above phenomena provide an analogy for the case of prestretched rubber where the slow release rate does not result in evident buckling while the high release rate induces severe buckles . Besides, it is found that the monolayer/bilayer WS 2 flakes transferred on quartz are easily fractured by the same quenching process (Figure S3).…”

“…The above phenomena provide an analogy for the case of prestretched rubber where the slow release rate does not result in evident buckling while the high release rate induces severe buckles. 44 Besides, it is found that the monolayer/bilayer WS a The TEC mismatch between quartz and TMDCs can be regarded as uniaxial along the y-axis since their TECs are very close along the zaxis. transferred on quartz are easily fractured by the same quenching process (Figure S3).…”

Wrinkling dynamics of fluctuating vesicles in time-dependent viscous flow

“…For a biophysically motivated choice of thermal fluctuations and sufficiently strong flows, we find excellent agreement with two-dimensional cross-sections of vesicles in experiments of Kantsler et al 6 . We also believe that our work could aid in understanding the effects that fluctuations could play in other related problems involving, for example, microtubules 45,46 and thin films 47 .…”

Drop Spreading and Confinement in Swelling-Driven Folding of Thin Films

“…The signature feature of such folding is a high degree of localization, i.e., some regions of the film show high localized curvature and large out-of-plane deflection, whereas the rest of the film remains conformal with the flat substrate. Such folding is distinct from folds that form when a stiff film supported by a liquid or soft solid is subjected to severe compression. − In those cases, initial compression induces roughly sinusoidal wrinkles. Further compression causes some wrinkles to grow into localized folds while the rest of the film reverts to becoming flat.…”