Calculating the volume of elongated bubbles and droplets in microchannels from a top view image

Musterd, Michiel; Steijn, Volkert van; Kleijn, Chris R.; Kreutzer, Michiel T.

doi:10.1039/c4ra15163a

Cited by 54 publications

(47 citation statements)

References 32 publications

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“…From there, they can be tilted back and forth between horizontal and critical point without shape hysteresis. Although this behavior is more subtle for 3D droplets (see below), we have also observed it in experiments [15]. This absence of a hysteresis loop implies no dissipation: indeed, the quasistatic deformation of the droplet analyzed here ignores viscous dissipation and a stationary contact line does not dissipate energy [16].…”

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confidence: 56%

Droplets on Inclined Plates: Local and Global Hysteresis of Pinned Capillary Surfaces

et al. 2014

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Local contact line pinning prevents droplets from rearranging to minimal global energy, and models for droplets without pinning cannot predict their shape. We show that experiments are much better described by a theory, developed herein, that does account for the constrained contact line motion, using as an example droplets on tilted plates. We map out their shapes in suitable phase spaces. For 2D droplets, the critical point of maximum tilt depends on the hysteresis range and Bond number. In 3D, it also depends on the initial width, highlighting the importance of the deposition history. The diverse and complex shapes of raindrops on a window strikingly illustrate the difficulty in understanding shapes of droplets under the influence of surface tension and gravity. Early theoretical work by Laplace, Young, and Gauss [1] showed that at equilibrium, a droplet touches a solid surface at a unique angle, the Young contact angle θ Y . In practice, however, the contact angle of static droplets often deviates from the Young angle, because the contact line gets pinned on physical or chemical defects before it has equilibrated to the lowest energy [2]. This results in a net force at the contact line, which can, akin to friction, balance gravity or shear in static droplets or slow down moving droplets. The range over which the angle can vary is bracketed by a receding angle θ r and an advancing angle θ a , as has been observed for stationary droplets and moving droplets alike [3]. They depend on the density of surface defects [4] and are often treated as constants for a given liquid-substrate combination, although it is observed and understood that these parameters are in fact asymptotes for vanishing defect size relative to droplet size [5]. Contact lines with angles in the hysteresis range ½θ r ; θ a do not move, and this explains qualitatively why droplets can remain stuck. These immobile drops are not only fascinating to observe; the minimal force to set them in motion is highly relevant technically, e.g., for condensers, pesticide spraying and water-repelling surfaces [6].

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confidence: 56%

Droplets on Inclined Plates: Local and Global Hysteresis of Pinned Capillary Surfaces

et al. 2014

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“…We ignore the effect of the third dimension, which plays a role in the shape of interface. As we show in the Appendix, the contact angle observed from the microscope images is dependent on the position inside the triangular pattern, probably because of the curvature effects in the third dimension [31,32]. However, such effects have been currently ignored in the model since we assume θ to be independent of the third dimension.…”

Section: Resultsmentioning

confidence: 99%

“…We observe that θ flat is relatively constant across different patterns. In contrast, the contact angle within the triangular pattern walls θ left and θ right is larger than θ flat due to the effect of third dimension [20,31,32]. Moreover, θ left and θ right are observed to be dependent on the pattern geometry, and thus we chose θ = θ flat .…”

Section: Experimental Measurement Of Contact Anglesmentioning

confidence: 99%

Controlled liquid entrapment over patterned sidewalls in confined geometries

2017

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Liquid entrapment over patterned surfaces has applications in diagnostics, oil recovery, and printing processes. Here we study the process of oil displacement upon sequential injection of water over a photopatterned structure in a confined geometry. By varying the amplitude and frequency of triangular and sinusoidal patterns, we are able to completely remove oil or trap oil in varying amounts. We present a theoretical model based on geometrical arguments that successfully predicts the criterion for liquid entrapment and provides insights into the parameters that govern the physical process.

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“…This contact angle can be seen as counterintuitive because our glass channel has a hydrophilic wetting property. However, we believe this acute oil in water contact angle is because of (1) the presence of a thin layer of oil precoating the channel surface [41,42] and (2) a trapezoidal cross section from anisotropic etching of the glass channel [43]. We also perform the reverse-flow case, i.e., water displacement with oil for four different flow conditions, and obtain a consistent value of 95°subtended by the water with the channel sidewalls.…”

Section: Contact Angle (β) Of Oil In Water With Sidewallsmentioning

confidence: 88%

Creating Isolated Liquid Compartments Using Photopatterned Obstacles in Microfluidics

et al. 2017

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We propose a method to trap liquid (both oil and water) in a microchannel by sequentially injecting oil and water (or vice versa) over photopatterned obstacles with controlled wetting properties. We present a simple geometrical model to understand the liquid-entrapment process and predict the evolution of the water/oil interface over an obstacle. Our analysis provides an analytic solution that can successfully predict useful properties such as angular position of pinch-off and the amount of captured liquid. We show that we are able to obtain a liquid bridge over two circular obstacles, and we are also able to predict the condition for the formation of a bridge. We further demonstrate the effect of the obstacle shape and how a sudden change in gradient results in larger liquid entrapment. We also demonstrate the ability to entrap isolated liquid chambers for parallel experimentation.

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Calculating the volume of elongated bubbles and droplets in microchannels from a top view image

Abstract: We present a theoretical model to calculate the volume of bubbles and droplets in segmented microflows from given dimensions of the microchannel and measured lengths of bubbles and droplets.

Cited by 54 publications

References 32 publications

Droplets on Inclined Plates: Local and Global Hysteresis of Pinned Capillary Surfaces

Droplets on Inclined Plates: Local and Global Hysteresis of Pinned Capillary Surfaces

Controlled liquid entrapment over patterned sidewalls in confined geometries

Creating Isolated Liquid Compartments Using Photopatterned Obstacles in Microfluidics

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