Localization in an idealized heterogeneous elastic sheet

Gurmessa, Bekele; Croll, Andrew B.

doi:10.1039/c6sm01848c

Cited by 16 publications

(22 citation statements)

References 45 publications

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“…When the strain was smaller than 20%, the first microwrinkles did not form, and the second microwrinkles appeared only faintly (Figure a). The critical strain for the chiral microbuckling was in the range of 10–15%, which was similar to other cases with uniaxial stretching . Second, the flattening process conducted between two buckling stages was essential for the homogeneous formation of chiral patterns over a large area.…”

Section: Resultssupporting

confidence: 76%

“…The wavelengths of the microwrinkles are shown in Figure with changes in the UV/ozone exposure times. The wavelength was as a function of the thickness of the thin oxide layer, which gradually increased with the UV/ozone exposure . After the first stage of microbuckling (λ 1 ), the wavelength linearly increased from 46.7 ± 1.9 to 81 ± 2.5 µm for an increase from 20 to 40 min (blue squares in Figure ).…”

Section: Resultsmentioning

confidence: 97%

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Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Hwang

Kim

et al. 2019

Adv Funct Materials

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Nano-and microsized chiral materials are receiving significant attention because of their unique characteristics, which include chiroptical activities and enantioselective interactions with living materials. However, the realization of chiral morphologies in such small-scale materials has been an issue because of the complicated fabrication methods and limited material selection. In this study, a facile and reproducible method is developed for fabricating 3D chiral microwrinkles with twisted shapes by asymmetric and biaxial buckling. Soft polydimethylsiloxane (PDMS) substrates are asymmetrically stretched with angled biaxial strains and exposed to UV/ozone to prepare hard silica layers on top of the PDMS substrates to induce microwrinkles. The chiral shapes are controlled by changing the angle (θ) between the two strain axes and the UV/ozone exposure times (t 1 , t 2 ) in each stage of buckling. The 3D chiral microwrinkles are shaped like "fusilli pasta" and occupy an area of 1.5 cm × 1.5 cm. The patterned area can be easily scaled, and no innate chiral biomaterial is necessary. This method could be widely extended to the fabrication of diverse types of chiral materials for advanced optical and bio-applications.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 97%

Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Hwang

Kim

et al. 2019

Adv Funct Materials

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“…[ 18,19 ] Artificial thickness or modulus inhomogeneities of film‐substrate systems are frequently used to induce various complex arrays of localized patterns by mechanical loading. [ 20–22 ]…”

Section: Introductionmentioning

confidence: 99%

“…[ 13–17 ] Our results are also different from the disordered or artificially inhomogeneous systems where the localized patterns cannot evolve into homogeneous structures. [ 18–22 ] Second, complex 2D wrinkle array can be well controlled by independently tuning annealing temperature and mechanical strain. The wrinkle morphologies are different from those induced by traditional biaxial loading.…”

Section: Introductionmentioning

confidence: 99%

Harnessing Heterogeneous Wrinkles in Metal/Polydimethylsiloxane Film System by Combination of Mechanical Loading and Heat Treatment

Shan-xin

et al. 2020

Adv Materials Inter

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dehydration, and atrophy. Controlling wrinkle morphologies including orientation, wavelength, and amplitude is very important and necessary for various practical applications.Generally, the orientation of wrinkles is determined by the stress distribution of the film. Unidirectional strain results in stripe-like wrinkles perpendicular to the strain axis [4,5] while multidirectional strain leads to disordered labyrinth-like or ordered herringbone wrinkles. [6,7] Introduction of film impurity can induce local strain anisotropy and guide wrinkle orientation, achieving highly ordered wrinkle arrays. [8,9] The wavelength of wrinkles depends on the film thickness [10] and the modulus ratio of film to substrate. [11] It can range from submicron to macroscale (kilometers in tectonic plates for instance). The amplitude of wrinkles is directly proportional to the wavelength and the square root of strain. [12,13] The aspect ratio of wrinkle (the ratio of amplitude to wavelength) is merely dependent on the strain. The previous studies showed that the wrinkle amplitude or aspect ratio is usually uniform for a homogeneous sample. [4][5][6][7] As the compression is beyond a critical value (20-30%), the homogeneous wrinkles evolve into localized patterns such as folds, ridges, and delaminations. [13][14][15][16][17] Localized wrinkles can be also observed in disordered or heterogeneous films such as single-wall carbon nanotubes, glassy polymers, and diblock copolymers due to spontaneous strain localization. [18,19] Artificial thickness or modulus inhomogeneities of film-substrate systems are frequently used to induce various complex arrays of localized patterns by mechanical loading. [20][21][22] Although localized patterns in disordered or artificially inhomogeneous systems have been extensively investigated, the formation and evolution of heterogeneous wrinkles (with unequal wavelengths or amplitudes compared with the sinusoidal wrinkles) in a homogeneous system remain unknown up to now. In this study, we report a novel way to tailor the heterogeneous wrinkles in metal/polydimethylsiloxane (PDMS) bilayer system by the combination of mechanical loading and heat treatment. The novelty of this work is concluded as following. First, the heterogeneous wrinkles in this study spontaneously form at small strain condition and evolve into homogeneous structures as the compression increases. This process is in contrast to Spontaneous wrinkled surfaces in nature usually possess unique physical and chemical properties. Inspired by nature and stimulated by practical application, artificial wrinkle patterns have received increasing interest recently. Here, the controllable heterogeneous wrinkles in metal films deposited on polydimethylsiloxane substrates by combination of mechanical loading and heat treatment is reported. It is found that the wrinkles are spontaneously localized at small strain condition due to the uneven distribution of wrinkle amplitudes on the film surface. The morphological features and underlying mechanisms of such wrink...

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“…Defects are experimentally inevitable and likely to affect the formation of wrinkles or localizations. 20,21 Among the limited literatures, intensive studies focused on elastically heterogeneity of thin film including patterned holes 22,23 and rigid elements 24,25 where the wrinkling pattern is disordered in the distance scaling with characteristic wavelength. However, the influence of defects inside the substrate on controlling the surface patterns of bilayer has not received much attention.…”

Section: Introductionmentioning

confidence: 99%

Unconventional localization prior to wrinkles and controllable surface patterns of film/substrate bilayers through patterned cavities

Liao

Chen

Nagakura

et al. 2018

Extreme Mechanics Letters

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A novel bilayer is introduced, consisting of a stiff film adhered to a soft substrate with patterned holes beneath the film/substrate interface. To uncover the transition of surface patterns, twodimensional plane strain simulations are performed on the defected bilayer subjected to uniaxial compression. Although the substrate is considered as the linear elastic material, the presence of defects can directly trigger the formation of locally ridged and then folding configurations from flat surface with a relatively small compressive strain. It is followed by the co-existing phases of folds and wrinkles under further overall compression. This phase transition reverses the traditional transition of wrinkle-to-ridge/fold for defect-free substrates. It's also found that the onset of initial bifurcation is highly dependent on the spatial configuration and geometries of holes, since the interaction of defects allows more strain-relief mechanisms beyond wrinkling. Furthermore, a rich diversity of periodic surface topologies, including overall waves, localizations, saw-like and coexisting features of folds and wrinkles can be obtained by varying the diameter, depth and spacing of holes as well as compressive strain, which provides a potential approach to engineer various surface patterns for applications.

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Localization in an idealized heterogeneous elastic sheet

Cited by 16 publications

References 45 publications

Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Harnessing Heterogeneous Wrinkles in Metal/Polydimethylsiloxane Film System by Combination of Mechanical Loading and Heat Treatment

Unconventional localization prior to wrinkles and controllable surface patterns of film/substrate bilayers through patterned cavities

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