Surface forces action in a vicinity of three phase contact line and other current problems in kinetics of wetting and spreading

Starov, Victor

doi:10.1016/j.cis.2010.02.002

Cited by 41 publications

(45 citation statements)

References 44 publications

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“…This equation represents the so-called Derjaguin-Frumkin equation (Starov et al 2007), relating the Young angle to the microscopic forces close to the contact line: γ cos θ Y = γ cos θ µ + φ µ (h = 0), where θ µ represents the microscopic angle at the contact line and we have used h x | x0 = tan θ µ and Young equation γ sg − γ sl = γ cos θ Y (Yeh et al 1999;Starov et al 2007;Starov 2010). The above two constraints on continuity of the energy and the augmented Young equation lead to h x (x 0 ) = 0, or θ µ = 0.…”

Section: Introductionmentioning

confidence: 99%

Thin films in partial wetting: stability, dewetting and coarsening

et al. 2018

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A uniform nanometric thin liquid film on a solid substrate can become unstable due to the action of van der Waals (vdW) forces. The instability leads to dewetting of the uniform film and the formation of drops. To minimize the total free energy of the system, these drops coarsen over time until one single drop remains. Here, using a thermodynamically consistent framework, we derive a new model for thin films in partial wetting with a free energy that resembles the Cahn–Hilliard form with a height-dependent surface tension that leads to a generalized disjoining pressure, and revisit the dewetting problem. Using both linear stability analysis and nonlinear simulations we show that the new model predicts a slightly smaller critical instability wavelength and a significantly (up to six-fold) faster growth rate than the classical model in the spinodal regime; this faster growth rate brings the theoretical predictions closer to published experimental observations. During coarsening at intermediate times, the dynamics become self-similar and model-independent; we therefore observe the same scalings in both the classical (with and without thermal noise) and new models. Both models also lead to a mean-field Lifshitz–Slyozov–Wagner (LSW)-type droplet-size distribution at intermediate times for small drop sizes. We, however, observe a skewed drop-size distribution for larger drops in the new model; while the tail of the distribution follows a Smoluchowski equation, it is not associated with a coalescence-dominated coarsening, calling into question the association made in some earlier experiments. Our observations point to the importance of the height dependence of surface tension in the early and late stages of dewetting of nanometric films and motivate new high-resolution experimental observations to guide the development of improved models of interfacial flows at the nanoscale.

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Section: Introductionmentioning

confidence: 99%

Thin films in partial wetting: stability, dewetting and coarsening

et al. 2018

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“…We recently presented static equilibrium computations of droplets with multiple contact lines, wetting geometrically patterned solid surfaces [29][30][31] . According to our approach, the liquid/ambient (LA) and the liquid/solid interfaces are treated in a unified context (one equation for both interfaces) by: a) employing the Young-Laplace equation 32 augmented with a disjoining (or Derjaguin) pressure term 33,34 , which accounts for the micro-scale liquid/solid interactions, and b) parameterizing the liquid surface in terms of its arc-length of the effectively onedimensional droplet profile.…”

Section: Introductionmentioning

confidence: 99%

Droplet spreading on rough surfaces: Tackling the contact line boundary condition

et al. 2016

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The complicated dynamics of the contact line of a moving droplet on a solid substrate often hamper the efficient modeling of microfluidic systems. In particular, the selection of the effective boundary conditions, specifying the contact line motion, is a controversial issue since the microscopic physics that gives rise to this displacement is still unknown. Here, a sharp interface, continuum-level, novel modeling approach, accounting for liquid/solid micro-scale interactions assembled in a disjoining pressure term, is presented. By following a unified conception (the model applies both to the liquid/solid and the liquid/ambient interfaces), the friction forces at the contact line, arXiv:1601.06540v1 [cond-mat.soft]

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“…In addition, the exponents 1 C and 2 C control the range of the molecular interactions (large 1 C and 2 C reduce the range within which these interactions are active. The distance, δ , between the liquid and the solid surface determines whether the disjoining pressure is attractive (modeling van der Waals interactions, for relatively large δ ) or repulsive (modeling steric forces and electrostatic interactions determined by an overlapping of the electrical double layers, for small δ ) [28]. In the case of a perfectly flat solid surface, the distance, δ , is defined as the vertical distance of the liquid surface from the solid boundary.…”

Section: Problem Formulationmentioning

confidence: 99%

Effect of substrate topography, material wettability and dielectric thickness on reversible electrowetting

Chamakos

Karapetsas

Papathanasiou

2018

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Recent experiments by Kavousanakis et al., Langmuir, 2018 [1], showed that reversible electrowetting on superhydrophobic surfaces can be achieved by using a thick solid dielectric layer (e.g. tens of micrometers). It has also been shown, through equilibrium (static) computations, that when the dielectric layer is thick enough the electrostatic pressure is smoothly distributed along the droplet surface, thus the irreversible Cassie to Wenzel wetting transitions can be prevented. In the present work we perform more realistic, dynamic simulations of the electrostatically-induced spreading on superhydrophobic surfaces. To this end, we employ an efficient numerical scheme which enables us to fully take into account the topography of the solid substrate. We investigate in detail the role of the various characteristics of the substrate (i.e. the dielectric thickness, geometry and material wettability) and present relevant flow maps for the resulting wetting states. Through our dynamic simulations, we identify the conditions under which it is possible to achieve reversible electrowetting. We have found that not only the collapse (Cassie-Baxter to Wenzel) transitions but also the contact angle hysteresis of the substrate significantly affects the reversibility.

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Surface forces action in a vicinity of three phase contact line and other current problems in kinetics of wetting and spreading

Abstract: Citation: STAROV, V., 2010. Surface forces action in a vicinity of three phase contact line and other current problems in kinetics of wetting and spreading.

Cited by 41 publications

References 44 publications

Thin films in partial wetting: stability, dewetting and coarsening

Thin films in partial wetting: stability, dewetting and coarsening

Droplet spreading on rough surfaces: Tackling the contact line boundary condition

Effect of substrate topography, material wettability and dielectric thickness on reversible electrowetting

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