Transformations in Wrinkle Patterns: Cooperation between Nanoscale Cross-Linked Surface Layers and the Submicrometer Bulk in Wafer-Spun, Plasma-Treated Polydimethylsiloxane

Evensen, Harold T.; Jiang, Hongrui; Gotrik, Kevin W.; Dénès, F.; Carpick, Robert W.

doi:10.1021/nl901136u

Cited by 36 publications

(41 citation statements)

References 37 publications

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“…Spontaneous surface wrinkling is formed by the mechanical instabilities of a compressed thin film attached to a soft foundation . One strategy to construct such surface wrinkles is to thermally or mechanically expand a foundation and then deposit a thin layer of stiff materials onto the prestrained foundation, or modify the top skin layer with external sources such as flame, reactive ion etching, plasma, electrochemical polymerization, or UV ozone to increase the modulus of the skin layer. A subsequent release of the prestrained foundation yields compressive strain on the skin layer, resulting in surface wrinkles.…”

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confidence: 99%

Microarchitecture for a Three‐Dimensional Wrinkled Surface Platform

Hakimi

Pérez

et al. 2015

Advanced Materials

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surfaces and may not be applicable to fabrication of 3D wrinkled surfaces. The fi rst strategy may introduce local stress concentrations on 3D surface as the substrate is globally stretched and thus may form undesired wrinkles on the surface. The second one has the potential to create wrinkles on curved surfaces, but it generates wrinkles on the surfaces without 3D spatial control. [ 35,36 ] Methods that can facilely make 3D microstructured surfaces with tunable and controllable wrinkles are still not available, essentially limiting their applications to planar surface. Given the distinctive morphology of wrinkles and its proven functional roles in various 2D applications, creation of artifi cial 3D wrinkled surfaces, mimicking the diverse morphologies of wrinkles on nonplanar surfaces appearing in nature, may offer enhanced surface platforms and extend current 2D applications into a new dimension.Here, we demonstrate the formation of spatially tunable and controllable wrinkles on 2D/3D microstructured surfaces. In this microfabrication, fi rst we use photolithography to create polymeric 3D features with conformal partially-cured-polymer (PCP) layers by applying precisely controlled UV exposure. By projecting UV light via a photomask, we polymerize a prepolymer solution of poly(ethylene glycol) diacrylate (PEG-DA) in between a glass substrate and a PDMS slit channel ( Figure S1, Supporting Information) to create the 2D and 3D surfaces. The initial presence of oxygen in the prepolymer solution inhibits the polymerization until the oxygen is gradually depleted by the UV-initiated free radicals. [ 37 ] Because of the continuous diffusion of oxygen from the surrounding environment via the PDMS while no oxygen has penetrated from the glass, nonuniform polymerization across the channel height occurs and a PCP layer is created. The polymerization starts from the glass side and grows with a partially cured outer layer where the oxygen is being consumed by the UV-initiated free radicals (see the simulation of the polymerization progress in Figure S2, Supporting Information). When the UV is turned off, the polymerization stops and a photomask-defi ned 2D/3D microstructure is formed with a cured-body (foundation) and a PCP layer. This PCP layer is comprised of a semi-crosslinked PEG polymer network and uncured monomers trapped inside the network. The layer thickness is determined by the UV exposure time ( Figure S2, Supporting Information). After applying the photolithography, we gently rinse the sample to remove the uncured monomers, while retain those monomers trapped in the PCP layer. Finally, we treat the sample surface with plasma to create 2D/3D wrinkled microstructures (see Experimental Section). The charged ions of the plasma crosslink the PCP layer and slightly modify its mechanical properties, turning the PCP layer into a thin crust. Moreover, the continuous plasma also expands the thin crust, thus introduces in-plane compressive stresses in the Surface wrinkles are ubiquitous in nature and are used as a strategy ...

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confidence: 99%

Microarchitecture for a Three‐Dimensional Wrinkled Surface Platform

Hakimi

Pérez

et al. 2015

Advanced Materials

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“…As the distance from the center to the edge of the wrinkle structure increases, the random labyrinth structure morphs into a 1D structure. The different morphologies on the same level plane were caused by gradually varying the internal stress along a specific direction 16 . According to the aforementioned pseudo-compressive strain and angular distribution, the compressive stress in a localized IB irradiation-induced wrinkle is affected by the distance from the edge.…”

Section: Resultsmentioning

confidence: 99%

Localized Ion-Beam Irradiation-Induced Wrinkle Patterns

Jeong

Park

Lee

et al. 2015

ACS Appl. Mater. Interfaces

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We observe a localized irradiation-induced wrinkle pattern on poly(dimethylsiloxane) (PDMS) via a long pattern mask. Localized ion-beam irradiation induces an inhomogeneous wrinkle pattern on the treated region. To confirm the inhomogeneity of the entire wrinkle pattern, its morphology was investigated using optical microscopy, which revealed separated regions in the wrinkle pattern. We used atomic force microscopy for quantitative analysis of the wrinkle pattern morphology and analyzed the angular distribution and the direction of compressive stress of the irradiated area. We confirmed the direction of stress release along the distance from the edges, and we achieved control of the orientation of the wrinkle pattern by altering the width of the irradiated area. Investigation of the inhomogeneities in a localized wrinkle formation provides an understanding of the formation mechanism to enhance its performance and application in various fields.

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“…In their work, the Ar plasma fulfilled two functions, (1) it crosslinked the PDMS film and (2) it formed a thin silica surface layer with a higher elastic modulus than that of the remaining polymer. 22 Recently, Lee et al…”

Section: Pegda Wrinklingmentioning

confidence: 99%