Kinetic study of a swelling-induced network of folds in a cross-linked PS-PDMS film

Abstract

Constructing a network of folds in a cross-linked PS-PDMS film through combining mesostructural organization of PS-PDMS and solvent-induced mechanical instability.

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

“…Upon evaporation of the solvent, the film deswelled, but the folds did not disappear (Figure b) indicating that reverse sliding is prevented, either by film–substrate adhesion or by film self-adhesion over the self-contacting region along the underside of the fold. Similar folding has been observed in swollen hydrogels, − other polymer films, − in strained, crosslinked polymer brushes, in metal films on solvent-swollen substrates, and in growing bacterial biofilms . 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.…”

“…Accordingly, the gap volume under the debonded film is constrained to be zero, and the strain energy can only be released into a self-contacting fold (Figure b). Despite a number of articles showing the type of folding discussed here, − , buckling subject to the no-gap constraint is not well understood. Here, we present a simplified model for the critical swelling ratio, λ c , needed to initiate folds under the no-gap constraint.…”

“…Thin films under compression can undergo a variety of instabilities including creases, wrinkles, localized folds, ridges, and delamination buckles. − The resulting structures have a wide variety of applications, including microscale patterning, surface property enhancement, and responsive materials . This article is about an unusual type of buckling behavior wherein a film resting on a rigid substrate, upon swelling with a solvent, forms highly localized folds. − The chief concern of this article is to explore finite-size effects, i.e., situations when only a small region of the film is allowed to swell.…”

Effectiveness of organic solvents for recovering collapsed PDMS micropillar arrays

“…Crosslinked PDMS was known to swell in some organic solvents, such as hexanes and toluene. 33,34 The swelling ratio was dened as the length ratio of the PDMS aer swelling to that before swelling. Some laboratories have suggested to use solvents with high swelling ratios to clean up PDMS residues on glass slides.…”

Swelling induced debonding of thin hydrogel films grafted on silicon substrates

“…For hydrogel films strongly anchored to the substrate, these swelling stresses were observed to induce instabilities on the free surface in the form of creases. [6][7][8][9] In situations where the film is not strongly bound to the substrate, swelling stresses can alternately result in delamination followed by large scale folding and blistering of the hydrogel films. Such mechanisms have been reported by Velankar et al 10 for poly(dimethylsiloxane) films swollen with toluene causing growth of sharp folds with a high aspect ratio.…”