Marangoni-driven film climbing on a draining pre-wetted film

Xue, Nan; Pack, Min; Stone, Howard A.

doi:10.1017/jfm.2019.1071

Cited by 8 publications

(7 citation statements)

References 32 publications

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“…However, τ ≥ 60 s, the measured data starts to deviate from Huppert’s solution with ≈25% difference in the film thickness, whereas the data agrees well with our model until the end of the measurement (≈230s). However, when the contact line slips faster after ≈60 s, the drainage length x 0 is significantly influenced by the contact line velocity, thus the film thickness decreases faster due to the dewetting effect as reported previously . Moreover, the curvature of the liquid film transverse to the flow is sufficiently small in our experiments similar to the results reported by Xue and Stone and thus the curvature is ignored as the film thickness is presumably uniform at the center where the drops impact as noted by the parallel lines of the inset figure in Figure (b).…”

Section: Experimental Methodssupporting

confidence: 82%

“…The liquid film thickness was extracted based on the interferometric pattern shift over time where the film thickness difference between two neighboring fringes is λ /(2 n w ), where n w = 1.33 is the refractive index of water. The interferometric patterns formed from the glass slide were neglected due to the small variation of the thickness …”

Section: Experimental Methodsmentioning

confidence: 99%

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Drop Bouncing Dynamics on Ultrathin Films

Tran

Pack

2021

Langmuir

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presented for the various drop impact regimes for the thin (i.e., O(1 μm))and thick (i.e., O(100 μm)) liquid film thickness limits. The incidence of the contact bouncing phenomenon was also characterized and found to be intimately tied to the late-stage gas film failure where a small volume of liquid is deposited onto the liquid film prior to bouncing. This study sheds new light on the bouncing-merging transitions for drops on ultrathin liquid films and gas entrainment dynamics relevant to applications such as precise drop deposition techniques.

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Section: Experimental Methodssupporting

confidence: 82%

Section: Experimental Methodsmentioning

confidence: 99%

Drop Bouncing Dynamics on Ultrathin Films

Tran

Pack

2021

Langmuir

Self Cite

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“…We propose that the Marangoni flow pulls the droplet contact line with a velocity on the order of u x , so that the position x f of the advancing front moves as . As a first approximation, we consider the primary edge of the advancing fluid front as a thin fluid layer of thickness h that is subjected to Marangoni stress in the x -direction and then the fluid velocity at the liquid surface results in , where μ is the fluid viscosity 53 , 60 . One may further assume a nearly constant surface tension difference Δ γ along the flow path, 55 , 60 , and thus the motion equation is written .…”

Section: Resultsmentioning

confidence: 99%

“…As a first approximation, we consider the primary edge of the advancing fluid front as a thin fluid layer of thickness h that is subjected to Marangoni stress in the x -direction and then the fluid velocity at the liquid surface results in , where μ is the fluid viscosity 53 , 60 . One may further assume a nearly constant surface tension difference Δ γ along the flow path, 55 , 60 , and thus the motion equation is written . After integration with the initial condition , t = t 0 , the front position results in , where is here defined as the Marangoni flow coefficient.…”

Section: Resultsmentioning

confidence: 99%

Droplets in underlying chemical communication recreate cell interaction behaviors

2022

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The sensory-motor interaction is a hallmark of living systems. However, developing inanimate systems with “recognize and attack” abilities remains challenging. On the other hand, controlling the inter-droplet dynamics on surfaces is key in microengineering and biomedical applications. We show here that a pair of droplets can become intelligently interactive (chemospecific stimulus-response inter-droplet autonomous operation) when placed on a nanoporous thin film surface. We find an attacker-victim-like non-reciprocal interaction between spatially separated droplets leading to an only-in-one shape instability that triggers a drop projection to selectively couple, resembling cellular phenomenologies such as pseudopod emission and phagocytic-like functions. The nanopore-driven underlying communication and associated chemical activity are the main physical ingredients behind the observed behavior. Our results reveal that basic features found in many living cell types can emerge from a simple two-droplet framework. This work is a promising step towards the design of microfluidic smart robotics and for origin-of-life protocell models.

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“…The plethora of observed coating patterns motivated a great deal of studies aimed at understanding the underlying physical mechanisms (Weinstein & Ruschak 2004). Typical examples include inertia-driven Kapitza waves (Kapitza 1948; Kapitza & Kapitza 1965), Marangoni effects due to gradients in surface tension (Oron 2000; Hosoi & Bush 2001; Scheid 2013; Xue, Pack & Stone 2020) and the formation of drops (Rayleigh 1882; Taylor 1950; Fermigier et al. 1992; Chandrasekhar 2013; Jambon-Puillet et al.…”

Section: Introductionmentioning

confidence: 99%

Gravity-driven coatings on curved substrates: a differential geometry approach

et al. 2022

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Drainage and spreading processes in thin liquid films have received considerable attention in the past decades. Yet, our understanding of three-dimensional cases remains sparse, with only a few studies focusing on flat and axisymmetric substrates. Here, we exploit differential geometry to understand the drainage and spreading of thin films on curved substrates, under the assumption of negligible surface tension and hydrostatic gravity effects. We develop a solution for the drainage on a local maximum of a generic substrate. We then investigate the role of geometry in defining the spatial thickness distribution via an asymptotic expansion in the vicinity of the maximum. Spheroids with a much larger (respectively smaller) height than the equatorial radius are characterized by an increasing (respectively decreasing) coating thickness when moving away from the pole. These thickness variations result from a competition between the variations of the substrate's slope and mean curvature. The coating of a torus presents larger thicknesses and a faster spreading on the inner region than on the outer region, owing to the different curvatures in these two regions. In the case of an ellipsoid with three different axes, spatial modulations in the drainage solution are observed as a consequence of a faster drainage along the short principal axis, faithfully reproduced by a three-dimensional asymptotic solution. Leveraging the conservation of mass, an analytical solution for the average spreading front is obtained. The solutions are in agreement with numerical simulations and experimental measurements obtained from the coating of a curing polymer on diverse substrates.

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Marangoni-driven film climbing on a draining pre-wetted film

Cited by 8 publications

References 32 publications

Drop Bouncing Dynamics on Ultrathin Films

Drop Bouncing Dynamics on Ultrathin Films

Droplets in underlying chemical communication recreate cell interaction behaviors

Gravity-driven coatings on curved substrates: a differential geometry approach

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