Microchannel Induced Surface Bulging of a Soft Elastomeric Layer

Majumder, Abhijit; Tiwari, Anurag Kumar; Korada, Krishnarao; Ghatak, Ajoy

doi:10.1201/b12181-25

Cited by 7 publications

(9 citation statements)

References 20 publications

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“…It is further proposed that a long wavelength instability can affect the mode of fracture as well as the adhesive strength of a soft adhesive confined between two rigid substrates in nontrivial ways. The normal components of the strain and stress are given in equations 14 and 15 respectively: (14) (15) Now setting the stresses tangential to the surface of the ball to zero, i.e.…”

Section: Discussionmentioning

confidence: 99%

Direct Measurement of the Surface Tension of a Soft Elastic Hydrogel: Exploration of Elastocapillary Instability in Adhesion

Chakrabarti

Chaudhury

2013

Langmuir

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An adhesively stressed thin film of a soft hydrogel confined between two rigid flat substrates auto-roughens with its dominant wavelength () exhibiting pronounced dependence on the film thickness (H). A linear stability analysis confirmed that this long wavelength instability (~7H) is due to an elasto-capillary effect, the implementation of which required direct measurements of the surface tension and the elasticity of the gel. The surface tension of the gel was estimated from the fundamental spherical harmonic of a hemispherical cap of the gel that was excited by an external noise. The shear modulus () of the gel was determined from its resonant shear mode in a confined geometry. During the course of this study, it was found that a high density steel ball submerges itself inside the gel by balancing its excess weight with the accumulated strain induced elastic force that allows another estimation of its elastic modulus. The large ratio (1.8 mm) of the surface tension to its elasticity ascertains the role of elasto-capillarity in the adhesion induced pattern formation with such gels. Experimental results are in accord with a linear stability analysis that predicts that the rescaled wavelength 27 . 0

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Section: Discussionmentioning

confidence: 99%

Direct Measurement of the Surface Tension of a Soft Elastic Hydrogel: Exploration of Elastocapillary Instability in Adhesion

Chakrabarti

Chaudhury

2013

Langmuir

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“…In such cases, a large length scale emerges from the competition between gravity and capillarity that rules the range of interaction between particles dispersed on a liquid surface when the Bond number of the system is comparable to or greater than unity. Co-operative effects of surface tension and elasticity give rise to a plethora of other interesting phenomena [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] .…”

Section: Introductionmentioning

confidence: 99%

Surface Folding-Induced Attraction and Motion of Particles in a Soft Elastic Gel: Cooperative Effects of Surface Tension, Elasticity, and Gravity

Chakrabarti

Chaudhury

2013

Langmuir

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ABSTRACT:We report, for the first time, some experimental observations regarding a new type of long range interaction between rigid particles that prevails when they are suspended in an ultrasoft elastic gel. A denser particle submerges itself to a considerable depth inside the gel and becomes elasto-buoyant by balancing its weight against the elastic force exerted by the surrounding medium. By virtue of a large elasto-capillary length, the surface of the gel wraps around the particle and closes to create a line singularity connecting the particle to the free surface of the gel. Substantial amount of tensile strain is thus developed in the gel network parallel to the free surface that penetrates to a significant depth inside the gel. The field of this tensile strain is rather long range owing to a large gravito-elastic correlation length and strong enough to pull two submerged particles into contact. The particles move towards each other with an effective force following an inverse linear distance law. When more monomers or dimers of the particles are released inside the gel, they orient rather freely inside the capsules they are in, and attract each other to form close packed clusters. Eventually, these clusters themselves interact and coalesce. This is an emergent phenomenon in which the gravity, the capillarity and the elasticity work in tandem to create a long range interaction. We also present the results of a related experiment, in which a particle suspended inside a thickness graded gel moves accompanied by the continuous folding and the relaxation of the gel's surface.

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“…For example, an incompressible elastic film, embedded with liquid-filled microstructures, bulges out considerably because of wetting (22,23). The deflection of a flat, thin, circular elastomeric film of thickness t in contact with a liquid drop of radius c gets amplified by geometric ratio (24) ðc=tÞ: δ ∼ ðσ=μÞðc=tÞ; here σ denotes the summation of bulk and surface stresses present in the film.…”

Section: Significancementioning

confidence: 99%

Estimation of solid–liquid interfacial tension using curved surface of a soft solid

Mondal

Phukan

Ghatak

2015

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

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Unlike liquids, for crystalline solids the surface tension is known to be different from the surface energy. However, the same cannot be said conclusively for amorphous materials like soft cross-linked elastomers. To resolve this issue we have introduced here a direct method for measuring solid-liquid interfacial tension by using the curved surface of a solid. In essence, we have used the inner surface of tiny cylindrical channels embedded inside a soft elastomeric film for sensing the effect of the interfacial tension. When a liquid is inserted into the channel, because of wetting-induced alteration in interfacial tension, its thin wall deflects considerably; the deflection is measured with an optical profilometer and analyzed using the Föppl-von Kármán equation. We have used several liquids and cross-linked poly(dimethylsiloxane) as the solid to show that the estimated values of the solid-liquid interfacial tension matches with the corresponding solid-liquid interfacial energy reasonably well.soft solid | surface tension | surface energy | bulging | wetting S urface energy of a material is the energy required to create a unit area of new surface by the process of division, whereas surface tension is the isotropic surface stress associated with its deformation. For liquid, these two quantities are numerically equal because, when a liquid surface is deformed, the separation distances between molecules at the surface do not necessarily alter as molecules can move from the bulk to a deforming surface. It is generally not so for a solid, as it has been argued (1-3) that a solid surface consists of a constant number of atoms, so the work done to alter the separation distance between atoms at the surface is expected to depend on this distance itself. As a result, work of deformation is not necessarily the same as the thermodynamic work required to create a new surface. It is not clear, however, if this picture is true for all kinds of solids. For crystal surfaces the question is somewhat resolved as it has been shown both experimentally and theoretically (2, 4) that surface free energy is a function of area itself and therefore the surface tension is expected to be different from surface energy. However, for amorphous materials, like polymeric solids and cross-linked elastomers, the issue remains unresolved because, for these materials, the molecules can have local mobility which allows them to show liquid-like behavior, e.g., surface reconstruction in response to external cues (5, 6). It has not been possible, however, to state anything conclusively because for most solids surface tension has not been measured accurately. The difficulty arises because, when a solid deforms due to the application of external forces, the internal stresses at the bulk of it far exceed that at the surface (7), which prevents the estimation of surface tension. Even when the sole effect of surface tension is considered, for most solids it remains almost immeasurable as the deformation due to surface tension remains significantly small.In ...

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Microchannel Induced Surface Bulging of a Soft Elastomeric Layer

Cited by 7 publications

References 20 publications

Direct Measurement of the Surface Tension of a Soft Elastic Hydrogel: Exploration of Elastocapillary Instability in Adhesion

Direct Measurement of the Surface Tension of a Soft Elastic Hydrogel: Exploration of Elastocapillary Instability in Adhesion

Surface Folding-Induced Attraction and Motion of Particles in a Soft Elastic Gel: Cooperative Effects of Surface Tension, Elasticity, and Gravity

Estimation of solid–liquid interfacial tension using curved surface of a soft solid

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