Slip-mediated dewetting of polymer microdroplets

McGraw, Joshua D.; Chan, Tak Shing; Maurer, Simon; Salez, Thomas; Benzaquen, Michael; Raphaël, Élie; Brinkmann, Martin; Jacobs, Karin

doi:10.1073/pnas.1513565113

Cited by 30 publications

(35 citation statements)

References 67 publications

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“…The nonsphericity of the droplet increases when the slip length is first decreased from the full slip limit. Further decreasing the slip length, we observe a new feature with respect to previous works (McGraw et al 2016): the non-sphericity reaches a maximum and then starts to decrease. This behavior is demonstrated for different equilibrium contact angles.…”

Section: Introductionsupporting

confidence: 48%

“…In this article, by extending the theoretical work of McGraw et al (2016), we elucidate the transition between the quasistatic and non-quasistatic evolutions of a dewetting droplet. We study the dewetting of a viscous droplet for a wide range of slip lengths and various equilibrium contact angles using the boundary element method.…”

Section: Introductionmentioning

confidence: 97%

“…A recent experimental and theoretical study on dewetting polymer microdroplets (McGraw et al 2016) showed that the transient droplet shape evolution, in the regime where the slip length is comparable to or larger than the typical droplet size, is much richer than one expects under the assumptions of quasistatic profiles and dissipation localized near the contact line. The transient droplet profiles are indeed found to be non-spherical (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Morphological evolution of microscopic dewetting droplets with slip

et al. 2017

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We investigate the dewetting of a droplet on a smooth horizontal solid surface for different slip lengths and equilibrium contact angles. Specifically, we solve for the axisymmetric Stokes flow using the boundary element method with (i) the Navier-slip boundary condition at the solid/liquid boundary and (ii) a time-independent equilibrium contact angle at the contact line. When decreasing the rescaled slip length $\tilde{b}$ with respect to the initial central height of the droplet, the typical non-sphericity of a droplet first increases, reaches a maximum at a characteristic rescaled slip length $\tilde{b}_{m}\approx O(0.1{-}1)$ and then decreases. Regarding different equilibrium contact angles, two universal rescalings are proposed to describe the behaviour of the non-sphericity for rescaled slip lengths larger or smaller than $\tilde{b}_{m}$. Around $\tilde{b}_{m}$, the early time evolution of the profiles at the rim can be described by similarity solutions. The results are explained in terms of the structure of the flow field governed by different dissipation channels: elongational flows for $\tilde{b}\gg \tilde{b}_{m}$, friction at the substrate for $\tilde{b}\approx \tilde{b}_{m}$ and shear flows for $\tilde{b}\ll \tilde{b}_{m}$. Following the changes between these dominant dissipation mechanisms, our study indicates a crossover to the quasistatic regime when $\tilde{b}$ is many orders of magnitude smaller than $\tilde{b}_{m}$.

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Section: Introductionsupporting

confidence: 48%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Morphological evolution of microscopic dewetting droplets with slip

et al. 2017

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“…Spreading of droplets in the partial-wetting regime can therefore serve as an alternative test for the height-dependence of surface tension; we have shown that our new model allows investigations of the spreading process without the need for precursor films (Pahlavan et al 2015). Visualization of the contactline motion at micro/nano-scales (Chen et al 2014;Qian et al 2015;McGraw et al 2016;Deng et al 2016) could therefore lead the way in refining and validating models for interfacial flows.…”

Section: Discussionmentioning

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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“…Hence, one might expect that, all other things equal, dewetting will occur more quickly as the film repellency of the solid is increased, for instance, by increasing θ e . Indeed, the first studies of dewetting reported a typical dewetting speed U / θ 3 e 4 , and subsequent experimental and theoretical studies of dewetting in the presence of a gas phase have either verified or assumed this result [5][6][7][8][9][10][11][12] .…”

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confidence: 99%

A viscous switch for liquid-liquid dewetting

et al. 2020

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The spontaneous dewetting of a liquid film from a solid surface occurs in many important processes, such as printing and microscale patterning. Experience suggests that dewetting occurs faster on surfaces of higher film repellency. Here, we show how, unexpectedly, a surrounding viscous phase can switch the overall dewetting speed so that films retract slower with increasing surface repellency. We present experiments and a hydrodynamic theory covering five decades of the viscosity ratio between the film and the surrounding phase. The timescale of dewetting is controlled by the geometry of the liquid-liquid interface close to the contact line and the viscosity ratio. At small viscosity ratio, dewetting is slower on low filmrepellency surfaces due to a high dissipation at the edge of the receding film. This situation is reversed at high viscosity ratios, leading to a slower dewetting on high film-repellency surfaces due to the increased dissipation of the advancing surrounding phase.

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Slip-mediated dewetting of polymer microdroplets

Cited by 30 publications

References 67 publications

Morphological evolution of microscopic dewetting droplets with slip

Morphological evolution of microscopic dewetting droplets with slip

Thin films in partial wetting: stability, dewetting and coarsening

A viscous switch for liquid-liquid dewetting

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