Area‐selective microwrinkle formation on poly(dimethylsiloxane) by treatment with strong acid

Abstract

Microwrinkles were formed by treating poly(dimethylsiloxane) (PDMS) surfaces with a mixture of concentrated sulfuric acid and nitric acid at 80 °C followed by a water rinsing step. The acid treatment oxidized the treated area, which also swelled owing to absorption of water during the rinsing step. This absorption of water induced a compressive stress on the PDMS surface that caused the formation of wrinkles. The appearance of wrinkles was controlled by the time interval between the end of the acid treatment and the beginning of the water rinsing step. Wrinkles were formed when the time interval was shorter than 5 s, as water was absorbed by the hygroscopic acid molecules within the treated surface. For longer time intervals of 300 s, this phenomenon was not observed. Based on these findings, a procedure for forming wrinkles in specific areas was developed by hydrating the chosen areas with wet filter paper cut into specific shapes after the acid treatment. The formation of wrinkles was confined to the area under the piece of paper. The orientation and alignment of the wrinkles at the boundaries were also characterized. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 167–174

Periodic fracture behaviour of nanomembranes

“…1a schematically illustrates our method for creating periodic fractures in a stiff/soft bilayer film, which involves simply peeling a pre-prepared bilayer film from a substrate with a 90° bending angle. The bilayer film generally consists of a stiff top layer and a soft substrate layer, which can be prepared by pasting or depositing a stiff membrane on a soft film 21,22 or directly hardening the surface of the soft film using plasma, 23,24 ions, 25 or strong acid/base 26 treatment. In this chapter, we prepared a bilayer film by treating a poly (dimethylsiloxane) (PDMS) film with oxygen (O 2 ) plasma 23 (see Methods and Materials).…”

Fabrication and Characterisation of Hydrogels with Reversible Wrinkled Surfaces for Limbal Study and Reconstruction

“…This was further supported through the proposition of the mode of action and thickness of stiffening imparted by the different methods of treatment. The acid oxidation was supposed to permeate deeper during acid immersion, imparting an increase in bulk stiffness throughout more of the material [31]. During plasma exposure, only the upper surface was exposed, and it formed a very fine brittle layer, which was found to be prone to cracking [32].…”

Surface Chemical Functionalization of Wrinkled Thiol–Ene Elastomers for Promoting Cellular Alignment

“…Through this approach, topography can be rapidly generated over large surface areas and has led to numerous applications, including optical and photovoltaic coatings, , switchable wetting surfaces, − tunable diffraction gratings, antifouling coatings, substrates for directed cell alignment, − and flexible optoelectronics, , among many others. Despite the versatility of wrinkling, the majority of studies have been limited to poly­(dimethylsiloxane) (PDMS) substrates, ,− which lack facile methods to confine and align wrinkle features. Moreover, control over surface chemistry, an important handle for enhancing material performance, is limited.…”