Non-linear dynamics of a viscoelastic film subjected to a spatially periodic electric field

Karapetsas, George; Bontozoglou, V.

doi:10.1016/j.jnnfm.2014.12.012

Cited by 8 publications

(5 citation statements)

References 48 publications

(72 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The set of algebraic equations is integrated in time with the implicit Euler method. The model has been implemented in COMSOL Multiphysics ® commercial software and has been cross-checked against our in-house FEM solver [73].…”

Section: Numerical Implementationmentioning

confidence: 99%

Efficient modelling of droplet dynamics on complex surfaces

Karapetsas

Chamakos

Papathanasiou

2016

J. Phys.: Condens. Matter

Self Cite

View full text Add to dashboard Cite

This work investigates the dynamics of droplet interaction with smooth or structured solid surfaces using a novel sharp-interface scheme which allows the efficient modelling of multiple dynamic contact lines. The liquid-gas and liquid-solid interfaces are treated in a unified context and the dynamic contact angle emerges simply due to the combined action of the disjoining and capillary pressure, and viscous stresses without the need of an explicit boundary condition or any requirement for the predefinition of the number and position of the contact lines. The latter, as it is shown, renders the model able to handle interfacial flows with topological changes, e.g. in the case of an impinging droplet on a structured surface. Then it is possible to predict, depending on the impact velocity, whether the droplet will fully or partially impregnate the structures of the solid, or will result in a 'fakir', i.e. suspended, state. In the case of a droplet sliding on an inclined substrate, we also demonstrate the built-in capability of our model to provide a prediction for either static or dynamic contact angle hysteresis. We focus our study on hydrophobic surfaces and examine the effect of the geometrical characteristics of the solid surface. It is shown that the presence of air inclusions trapped in the micro-structure of a hydrophobic substrate (Cassie-Baxter state) result in the decrease of contact angle hysteresis and in the increase of the droplet migration velocity in agreement with experimental observations for super-hydrophobic surfaces. Moreover, we perform 3D simulations which are in line with the 2D ones regarding the droplet mobility and also indicate that the contact angle hysteresis may be significantly affected by the directionality of the structures with respect to the droplet motion.

show abstract

Section: Numerical Implementationmentioning

confidence: 99%

Efficient modelling of droplet dynamics on complex surfaces

Karapetsas

Chamakos

Papathanasiou

2016

J. Phys.: Condens. Matter

Self Cite

View full text Add to dashboard Cite

show abstract

“…The influences of some process parameters, such as voltage, air gap, polymer properties, on the polymeric behavior have been well studied. Some conclusions have been revealed as guidance for a faithful structure . It is revealed that the large voltage, the small air gap, and the polymer with a large dielectric permittivity can generate a large L‐DEP pressure to promote the conformal deformation .…”

Section: Introductionmentioning

confidence: 99%

Investigation of the role of template features on the electrically induced structure formation (EISF) for a faithful duplication

et al. 2017

View full text Add to dashboard Cite

Electrically induced structure formation, as a physical approach to fabricate micro/nanostructures, has attracted much attention because of the simple process, low-cost, high-efficiency, and wide applications on electronics, microfluidics, and so forth. Hitherto, the influence of some process parameters, such as voltage, air gap, film thickness, polymer properties, on the polymeric behavior, and the structure formation has been explored, neglecting the effects of the template features, which affect the polymer deformation. Especially for the conductive protrusions directly contacting the polymer, the phenomenon of electric breakdown may occur, leading to a failure of structure formation. The limitation of the research on the template features triggers the necessity to study its influence for a faithful deformation. In this paper, three types of patterned template are studied based on the electric field at the air-polymer interface, consisting of completely conductive template, partially conductive template, and dielectric template. Comprehensive consideration of the electric intensity for a sufficient driving pressure and the leaky current for preventing damaging the polymer, some guiding opinions on the template material and geometry can be provided to design the patterned template for the electrically induced structure formation process with a purpose for a faithful structure.

show abstract

“…Karapetsas & Bontozoglou (2015) carried out 2D numerical calculations for a Newtonian fluid and a viscoelastic polymeric fluid under a patterned mask to find that perturbations grow until they reach the top electrode and viscoelasticity affects their wavelength.…”

Section: Introductionmentioning

confidence: 99%

Two-layer electrified pressure-driven flow in topographically structured channels

Dubrovina

Papageorgiou

2017

J. Fluid Mech.

View full text Add to dashboard Cite

The flow of two stratified viscous immiscible perfect dielectric fluids in a channel with topographically structured walls is investigated. The flow is driven by a stream wise pressure gradient and an electric field across the channel gap. This problem is explored in detail by deriving and studying a nonlinear evolution equation for the interface valid for large amplitude long waves in the Stokes flow regime. For flat walls the electrified flow is long-wave unstable with a critical cut-off wavenumber that increases linearly with the magnitude of the applied voltage. In the nonlinear regime it is found that the presence of pressure-driven flow prevents electrostatically induced interface touchdown that has been observed previously -time modulated nonlinear travelling waves emerge instead. When topography is present, linearly stable uniform flows become non-uniform spatially periodic steady states; a small amplitude asymptotic theory is carried out and compared with computations. In the linearly unstable regime intricate nonlinear structures emerge that depend, among other things, on the magnitude of the wall corrugations. For a low amplitude sinusoidal boundary, time modulated travelling waves are observed that are similar to those found for flat walls but are influenced by the geometry of the wall and slide over it without touching. The flow over a high amplitude sinusoidal pattern is also examined in detail and it is found that for sufficiently large voltages the interface evolves to large amplitude waves that span the channel and are subharmonic relative to the wall. A type of "walking" motion emerges that causes the lower fluid to wash through the troughs and create strong vortices over the peaks of the lower boundary. Nonuniform steady states induced by the topography are calculated numerically for moderate and large values of the flow rate, and their stability is analysed using Floquet theory. The effect of large flow rates is also considered asymptotically to find solutions that compare very well with numerical computations.

show abstract

Non-linear dynamics of a viscoelastic film subjected to a spatially periodic electric field

Cited by 8 publications

References 48 publications

Efficient modelling of droplet dynamics on complex surfaces

Efficient modelling of droplet dynamics on complex surfaces

Investigation of the role of template features on the electrically induced structure formation (EISF) for a faithful duplication

Two-layer electrified pressure-driven flow in topographically structured channels

Contact Info

Product

Resources

About