Instability and dewetting of ultrathin solid viscoelastic films on homogeneous and heterogeneous substrates

Patra, Ajoy and Bandyopadhyay, Dipankar and Tomar, Gaurav and Sharma, Ashutosh and Biswas, Gautam (2011) Instability and dewetting of ultrathin solid viscoelastic films on homogeneous and heterogeneous substrates. In: Journal of Chemical Physics, 134 (6).

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Abstract

Instability and dewetting engendered by the van der Waals force in soft thin (<100 nm) linear viscoelastic solid (e. g., elastomeric gel) films on uniform and patterned surfaces are explored. Linear stability analysis shows that, although the elasticity of the film controls the onset of instability and the corresponding critical wavelength, the dominant length-scale remains invariant with the elastic modulus of the film. The unstable modes are found to be long-wave, for which a nonlinear long-wave analysis and simulations are performed to uncover the dynamics and morphology of dewetting. The stored elastic energy slows down the temporal growth of instability significantly. The simulations also show that a thermodynamically stable film with zero-frequency elasticity can be made unstable in the presence of physico-chemical defects on the substrate and can follow an entirely different pathway with far fewer holes as compared to the viscous films. Further, the elastic restoring force can retard the growth of a depression adjacent to the hole-rim and thus suppress the formation of satellite holes bordering the primary holes. These findings are in contrast to the dewetting of viscoelastic liquid films where nonzero frequency elasticity accelerates the film rupture and promotes the secondary instabilities. Thus, the zero-frequency elasticity can play a major role in imposing a better-defined long-range order to the dewetted structures by arresting the secondary instabilities. (C) 2011 American Institute of Physics. doi: 10.1063/1.3554748]

Item Type:	Journal Article
Publication:	Journal of Chemical Physics
Publisher:	American Institute of Physics
Additional Information:	Copyright of this article belongs to American Institute of Physics.
Keywords:	elasticity, liquid films;stability;van der Waals forces; viscoelasticity;wetting
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	07 Apr 2011 08:21
Last Modified:	07 Apr 2011 08:21
URI:	http://eprints.iisc.ac.in/id/eprint/36018

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