Self‐structured serrated edges of chemically oxidized poly(dimethylsiloxane) disks

Abstract

Serrated structures on a micrometer scale were spontaneously formed along the edge of a poly(dimethylsiloxane) (PDMS) disk using the following procedure. First, a drop of PDMS prepolymer was placed on a glass slide, followed by vulcanization. Second, the obtained PDMS disk was soaked in a mixture of sulfuric acid and nitric acid to form a serrated structure. Consideration of the mechanism of the structure formation was based on the following results. (1) The acid oxidized the PDMS surface, which was then swollen with the acid mixture or water to form wrinkles. (2) The wrinkle wavelength depended on the thickness of the PDMS film. (3) The thickness of the PDMS disk varied near its edge because the meniscus of the drop of the PDMS prepolymer was retained after the vulcanization. These results suggest that the thickness gradient of the PDMS disk led to the spontaneous formation of a serrated edge structure.

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

“…As stated above, we believe that chemical reactions in solution are advantageous for wrinkling large surfaces of polymeric materials. In our previous articles, we reported that the chemical treatment of PDMS with a mixture of concentrated sulfuric acid and concentrated nitric acid formed wrinkles, even though PDMS is a chemically stable polymer . The infrared spectra of PDMS treated with the acid mixture revealed that the mixture oxidized PDMS and formed siloxane bonds .…”

“…Such homogeneity of irradiation is essential to create regular wrinkles because the wavelength of the wrinkles is determined by the thickness of the stiff, thin film . Consequently, we have studied chemical reactions in solution as an alternative technique for forming stiff, thin surface layers on polymeric materials because homogeneous solutions can easily be obtained by simply stirring the solutions …”

“…19 Consequently, we have studied chemical reactions in solution as an alternative technique for forming stiff, thin surface layers on polymeric materials because homogeneous solutions can easily be obtained by simply stirring the solutions. 20,21 Although forming regular wrinkles on a large area is still challenging, many attractive applications of micro-wrinkles have been proposed during the past decade. For example, superhydrophobic surfaces were obtained using wrinkled PDMS that was treated with oxygen plasma followed by dipcoating with silica nanoparticles.…”

“…In our previous articles, we reported that the chemical treatment of PDMS with a mixture of concentrated sulfuric acid and concentrated nitric acid formed wrinkles, even though PDMS is a chemically stable polymer. 20,21 The infrared spectra of PDMS treated with the acid mixture revealed that the mixture oxidized PDMS and formed siloxane bonds. 20 This method was first proposed by Shih et al, 29 but unfortunately well-ordered wrinkles could not be achieved.…”

Spontaneous formation of interdigitated array pattern in wrinkled gold films deposited on poly(dimethylsiloxane) elastomer

“…35 As material for the stiff, thin films, gold, 37,38 platinum 39 and aluminum 40 can be employed. Silica-like thin films that are formed on the surface of PDMS through exposure to oxygen plasma, 41 ultraviolet light 42,43 or acidic solution [44][45][46][47] are also used. For a soft, thick substrate, PDMS is one of the commonly used materials, probably because a microscopically flat surface is easily obtained by casting a liquid precursor of PDMS on a plate followed by vulcanizing the precursor.…”