Deterministic Switching of Hierarchy during Wrinkling in Quasi‐Planar Bilayers

Saha, Sourabh K.; Culpepper, Martin L.

doi:10.1002/adem.201600048

Cited by 5 publications

(5 citation statements)

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“…Among the structures used to study the wettability of anisotropic surface, wrinkled structures are the most common. [ 64–66 ] Previous works have studied the wettability of wrinkled surfaces from both theoretical [ 67,68 ] and experimental [ 69–72 ] perspectives. For the rigid wrinkled surface, once the surface is prepared, its wettability is difficult to change.…”

Section: Introductionmentioning

confidence: 99%

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Chai

Tian

et al. 2020

Adv Materials Inter

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Dynamical regulation to unidirectional wetting has received considerable attention in recent years due to its important role in flexible electronics, microfluidics, drug transportation, and so forth. It is of great significance to prepare a surface which allows the droplet to spread directionally on it with the length of droplet reversibly fluctuated within a broad range under external stimulation. In this paper, a double‐gradient wrinkled structure is prepared by constructing the structure‐gradient pillar arrays on a mechanics‐adjusted wrinkled surface and subsequently making chemical gradient by oxygen plasma treatment. Under the synergistic effect of the structural gradient, chemical gradient, and wrinkled structure, the droplet can undergo unidirectional spreading and realize dynamic regulation of the spreading length on the flexible structure. This will provide a propagable method for the regulation of surface wetting.

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Section: Introductionmentioning

confidence: 99%

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Chai

Tian

et al. 2020

Adv Materials Inter

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“…Among the structures used to study the wettability of soft materials, wrinkled structures are the most common. − With regard to theoretical research concerning wrinkled surfaces, Liu et al approximated a sine wave structure to study the relationship between the wrinkled size and surface wettability . This theory was further extended to the analysis of the influence of different structures on wettability .…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Study of Reversible and Stable Wetting States of a Hierarchically Wrinkled Surface Tuned by Mechanical Strain

et al. 2019

Langmuir

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The wetting behavior of hierarchically wrinkled surfaces has attracted great interest because of its broad application in flexible electronic, microfluidic chip, and biomedicine. However, theoretical studies concerning the relationship between the apparent contact angle and mechanical strain applied on the soft and flexible surface with a hierarchically wrinkled structure are still limited. We established a theoretical framework to describe and understand how prestrain and applied dynamic strain reversibly tune the wettability of the hierarchically wrinkled surface. More specifically, a direct relationship between the mechanical strain and contact angle was built through reversible tuning of the amplitude and the wavelength of the wrinkled structures caused by mechanical strain, which allowed for more precise adjustment of surface wettability. To verify the accuracy of the theoretical relationship between the contact angle and mechanical strain, a soft surface with a hierarchically wrinkled structure was prepared by combining wrinkled microstructures and strip ones. The results showed that the experimental contact angles were in agreement with the theoretical ones within a limited error range. This will be helpful for further investigation on the wettability of hierarchically wrinkled surfaces.

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“…The prepatterned region was fabricated by replicating a pre-existing wrinkled surface on top of PDMS during the curing process [25]. Wrinkled patterns were fabricated by (i) uniaxially stretching the PDMS base on a custom tensile stage [13], (ii) generating a thin glassy layer on top of the prestretched base by exposing it to air plasma [25,26], and (iii) releasing the stretch in the base layer to generate uniaxial compressive strain in the glassy thin film. As the entire bilayer was subjected to the same stretch and was exposed to air plasma at once, the two regions differ only in the presence or absence of the prepatterns.…”

Section: Physical Demonstrationmentioning

confidence: 99%

“…Modeling of wrinkle formation in prepatterned bilayers was performed on the perturbed mesh via a single-step nonlinear analysis. The perturbed mesh was generated from the prepattern geometry using a custom mesh-perturbation toolbox described in detail elsewhere [25,29].…”

Section: Finite Element Modelingmentioning

confidence: 99%

“…However, this concern can be overcome by the mode lock-in phenomenon that occurs during compression of prepatterned bilayers [29]. We have recently identified that the emergence of the hierarchical mode is preceded by a mode locked state wherein the prepattern mode persists [25,29]. When the prepattern period is "substantially similar" to the natural period, it is possible for the single-period mode to persist beyond the period doubling onset strain, as illustrated in Fig.…”

Section: Increase In Aspect Ratiomentioning

confidence: 99%

See 1 more Smart Citation

Geometric Prepatterning-Based Tuning of the Period Doubling Onset Strain During Thin-Film Wrinkling

Saha

2017

Journal of Applied Mechanics

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Wrinkling of thin films is an easy-to-implement and low-cost technique to fabricate stretch-tunable periodic micro and nanoscale structures. However, the tunability of such structures is often limited by the emergence of an undesirable period-doubled mode at high strains. Predictively tuning the onset strain for period doubling via existing techniques requires one to have extensive knowledge about the nonlinear pattern formation behavior. Herein, a geometric prepatterning-based technique is introduced that can be implemented even with limited system knowledge to predictively delay period doubling. The technique comprises prepatterning the film/base bilayer with a sinusoidal pattern that has the same period as the natural period of the system. This technique has been verified via physical and computational experiments on the polydimethylsiloxane (PDMS)/glass bilayer system. It is observed that the onset strain can be increased from the typical value of 20% for flat films to greater than 30% with a modest prepattern aspect ratio (2·amplitude/period) of 0.15. In addition, finite element simulations reveal that (i) the onset strain increases with increasing prepattern amplitude and (ii) the delaying effect can be captured entirely by the prepattern geometry. Therefore, one can implement this technique even with limited system knowledge, such as material properties or film thickness, by simply replicating pre-existing wrinkled patterns to generate prepatterned bilayers. Thus, geometric prepatterning is a practical scheme to increase the operating range of stretch-tunable wrinkle-based devices by at least 50%.

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Deterministic Switching of Hierarchy during Wrinkling in Quasi‐Planar Bilayers

Abstract: A u t h o r M a n u s c r i p t A u t h o r M a n u s c r i p t A u t h o r M a n u s c r i p t A u t h o r M a n u s c r i p t A u t h o r M a n u s c r i p t

Cited by 5 publications

References 29 publications

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Theoretical and Experimental Study of Reversible and Stable Wetting States of a Hierarchically Wrinkled Surface Tuned by Mechanical Strain

Geometric Prepatterning-Based Tuning of the Period Doubling Onset Strain During Thin-Film Wrinkling

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