Mechanical instability of gels at the phase transition

Tanaka, Toyoichi; Sun, Shao‐Tang; Hirokawa, Yoshitsugu; Katayama, Seiji; Kucera, John Paul; Hirose, Yoshiharu; Amiya, Takayuki

doi:10.1038/325796a0

Cited by 558 publications

(599 citation statements)

References 9 publications

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“…They exist in composite materials 1 , geological strata 2,3 , electronic devices 4 , biological tissues 5,6 and soft actuators 7 . In many cases, stresses arise due to differences in thermal expansion [8][9][10] , chemical reactions 11 , growth 5,12 , swelling 13 , or mechanical pre-strains 14 . Such mismatches may cause buckling instabilities 1, 10,15,16 , which can reduce the strength of structures 1,10,15,16 and lead to debonding of the interfaces 8,9,17 .…”

Section: Introductionmentioning

confidence: 99%

“…These wrinkles have dynamic analogs: Stoneley waves on the interface between two materials 18,[21][22][23] , and Rayleigh waves on the surface of a homogeneous material 21,24,25 . Wrinkles, however, have not been observed on surfaces of homogeneous elastic materials under compression; rather, creases have been observed 13,[26][27][28][29] . A recent theory shows that surface wrinkles and surface creases are two types of instability, and the critical strain for the onset of surface wrinkles is higher than that for the onset of surface creases 30 .…”

Section: Introductionmentioning

confidence: 99%

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Creases on the interface between two soft materials

et al. 2014

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Theory and experiment are presented to show that an interface between two soft materials under compression can form creases, a type of bifurcation distinct from wrinkles.While creases bifurcate from a state of flat interface by a deformation localized in space and large in amplitude, wrinkles bifurcate from a state of flat interface by a deformation nonlocal in space and small in amplitude. The interfacial creases set in at a lower critical compression than interfacial wrinkles, but higher than surface creases. The condition for the onset of interfacial creases is scale-free, and is calculated in terms of elastic moduli, pre-strains and applied strains.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Creases on the interface between two soft materials

et al. 2014

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“…Although mechanical self-assembly provides a low cost route for spontaneous generation of surface patterns, explorations to date have been focused on introducing surface roughness via wrinkling and crumpling instabilities. Here we show that surfaces can be spontaneously patterned with chemical patches with small changes in surface roughness by harnessing a reversible creasing instability (15)(16)(17).…”

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confidence: 99%

Spontaneous wettability patterning via creasing instability

Chen

McKinley

Cohen

2016

Proc. Natl. Acad. Sci. U.S.A.

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Surfaces with patterned wettability contrast are important in industrial applications such as heat transfer, water collection, and particle separation. Traditional methods of fabricating such surfaces rely on microfabrication technologies, which are only applicable to certain substrates and are difficult to scale up and implement on curved surfaces. By taking advantage of a mechanical instability on a polyurethane elastomer film, we show that wettability patterns on both flat and curved surfaces can be generated spontaneously via a simple dip coating process. Variations in dipping time, sample prestress, and chemical treatment enable independent control of domain size (from about 100 to 500 μm), morphology, and wettability contrast, respectively. We characterize the wettability contrast using local surface energy measurements via the sessile droplet technique and tensiometry.wettability contrast | creasing instability | domain size | morphology | curved surfaces S urfaces that juxtapose local hydrophilic areas with hydrophobic areas show superior performance compared with surfaces with homogeneous wettability in many industrial applications including heat transfer (1), water collecting (2-6), particle separation (7), and microfluidics (8). For instance, developing enhanced water-collecting efficiency has been inspired by the Namib desert beetle, which was reported (2) to have hydrophilic bumps on an overall wax-covered hydrophobic surface. Although the hydrophilic bumps reduce the nucleation/coalescence energy of microdroplets, the overall hydrophobic character of the surface facilitates the spontaneous shedding of water droplets when they grow beyond a certain size.To achieve surfaces with wettability patterning, traditional fabrication methods such as photolithography and soft lithography have been used. However, these methods are generally not cost-effective, not readily scaled up, require multiple process steps, and are difficult to implement on curved surfaces (3, 9). Recently, mechanical instabilities have been explored as a facile self-assembly approach to endow surfaces with superhydrophobicity (10-12), superhydrophilicity (13), or anisotropic wettability (14). Although mechanical self-assembly provides a low cost route for spontaneous generation of surface patterns, explorations to date have been focused on introducing surface roughness via wrinkling and crumpling instabilities. Here we show that surfaces can be spontaneously patterned with chemical patches with small changes in surface roughness by harnessing a reversible creasing instability (15-17).A creasing instability develops when a soft polymer network is placed under mechanical compression beyond a certain critical strain, at which point sharp folds spontaneously develop and grow on the deformable free surfaces (18). This process has been linked to the morphology development of the brain (19,20), electric breakdown of dielectric elastomers (21), and has also been harnessed to prepare switchable surfaces actuated by temperature (22) or electric ...

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“…As shown later, many SAP particles induce wrinkling of a sheet-like structure due to rapid swelling, which is different in behavior from previously-reported bulk gel systems. [10][11][12][13] …”

Section: Introductionmentioning

confidence: 99%

Rapid Swelling and Pattern Formation in Hydrogel Particles

Yamaguchi

2014

J. Soc. Rheol., Jpn

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Mechanical instability of gels at the phase transition

Cited by 558 publications

References 9 publications

Creases on the interface between two soft materials

Creases on the interface between two soft materials

Spontaneous wettability patterning via creasing instability

Rapid Swelling and Pattern Formation in Hydrogel Particles

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