Height of a liquid drop on a wetting stripe

Malijevský, Alexandr

doi:10.1103/physreve.102.052802

Cited by 4 publications

(3 citation statements)

References 52 publications

(69 reference statements)

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“…Further, as per the local approximation, the interaction potentials and repulsive pressure are functions of the local thickness and curvature of the interface. 27 These assumptions work well for a majority of systems such as the interfacial interaction due to the immersion of thin elastomeric wire into ethanol, 31 the adsorption in capped capillaries, 37 the coffee-ring pattern of suspended nanoparticles in drying droplets, 38 the wetting of a hydrophilic stripe, 39 and the interfacial thermodynamics of drops and bubbles on flat substrates. 40 However, when the interface is not sharp (for instance, a drop of liquid helium on a gold substrate that is coated with a thin cesium layer 41 ), the potential as defined in eq 2 needs to be amended to account for the variable correlations between the two phases.…”

Section: ■ Conclusionmentioning

confidence: 98%

Density Functional Theory Approach to Interpret Elastowetting of Hydrogels

Chakraborty,

Mitra,

Kim

et al. 2024

Langmuir

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Sessile hydrogel drops on rigid surfaces exhibit a wetting/contact morphology intermediate between liquid drops and glass spheres. Using density functional theory, we reveal the contact forces acting between a hydrogel and a rigid glass surface. We show that while transitioning from liquid-like to solid-like hydrogels, there exists a critical hydrogel elasticity that enables a switch from attractive-to-repulsive interaction with the underlying rigid glass surface. Our theoretical model is validated by experimental observations of sessile polyacrylamide hydrogels of varying elasticity on glass surfaces. Further, the proposed model successfully approaches Young's law in the pure liquid limit and work of adhesion in the glassy limit. Lastly, we show a modified contact angle relation, taking into account the hydrogel elasticity to explain the features of a distinct hydrogel foot.

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Section: ■ Conclusionmentioning

confidence: 98%

Density Functional Theory Approach to Interpret Elastowetting of Hydrogels

Chakraborty,

Mitra,

Kim

et al. 2024

Langmuir

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“…We also want to point out, that there are similarities to the filling transitions which are observed if a wall with surface asperities is exposed to vapor and is partially filled by the coexisting liquid phase (see, e.g., Refs. [58][59][60][61]). The correspondence is less obvious in this case, due to different conditions and dependences studied in these investigations.…”

Section: Model Systemmentioning

confidence: 99%

Intrusion of liquids into liquid infused surfaces with nanoscale roughness

Singh¹,

Schimmele²,

Dietrich³

2021

Preprint

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We present a theoretical study of the intrusion of an ambient liquid into the pores of a nanocorrugated wall w. The pores are prefilled with a liquid lubricant which adheres to the walls of the pores more strongly than the ambient liquid does. The two liquids are modeled as a binary liquid mixture of two species of particles, A and B. The mixture can decompose into a liquid rich in A particles, representing the ambient liquid, and another one rich in B particles, representing the liquid lubricant. The wall is taken to attract the B particles more strongly than the A particles.The ratio w-A/w-B of these interaction strengths is changed in order to tune the contact angle θ AB formed by the A-rich/B-rich liquid interface between the two fluids and a planar wall, composed of the same material as the one forming the pores. We use classical density functional theory, in order to capture the effects of microscopic details on the intrusion transition, which occurs as the concentration of the minority component or the pressure in the bulk of the ambient liquid is varied, moving away from bulk liquid-liquid coexistence within the single-phase domain of the A-rich bulk ambient liquid. These liquid structures have been studied as a function of the contact angle θ AB and for various widths and depths of the pores. We also studied the reverse process in which a pore initially filled with the ambient liquid is refilled with the liquid lubricant. The location of the intrusion transition, with respect to its dependence on the contact angle θ AB and the width of the pore, qualitatively follows the corresponding shift of the capillary-coexistence line away from the bulk liquid-liquid coexistence line, as predicted by a macroscopic capillarity model.Quantitatively, the transition found in the microscopic approach occurs somewhat closer to the bulk liquid-liquid coexistence line than predicted by the macroscopic capillarity model. The quantitative discrepancies become larger for narrower cavities. In cases in which the wall is completely wetted by the lubricant (θ AB = 0) and for small contact angles the reverse transition follows the same path as for intrusion; there is no hysteresis. For larger contact angles hysteresis is observed. The width of the hysteresis increases with increasing contact angle. A reverse transition is not found inside the domain within which the ambient liquid forms a single phase in the bulk, once θ AB exceeds a geometry dependent threshold value. According to the macroscopic capillarity theory, for the considered geometry, this is the case for θ AB > 54.7 • . Our computations show, however, that nanoscale effects shift this threshold value to much higher values. This shift increases strongly if the widths of the pores become smaller (below about ten times the diameter of the A and B particles).

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“…While wrinkled substrates without gradients [32][33][34][35][36][37][38][39] and substrates of similar geometries [40][41][42][43][44][45][46] have been studied in different contexts, rugotaxis has remained unexplored. Inspired by the work of Hiltl and Böker [28], we employ theoretical [47,48] and molecular dynamics (MD) [17] modelling to investigate the self-propelled motion of nanodroplets on wrinkled, solid substrates with wavelength gradient characterising the wrinkles.…”

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confidence: 99%

Rugotaxis: Droplet motion without external energy supply

Theodorakis¹,

Егоров²,

Milchev³

2022

EPL

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Nano-patterned substrates offer possibilities for controlling the motion of fluids without external energy supply in novel technologies in microfluidics, coatings,etc. Here, we report on the rugotaxial motion of droplets on wrinkled substrates with gradient in the wavelength of the wrinkles by exploring a broad range of parameters, such as amplitude of the wrinkles, substrate wettability, droplet size and wavelength gradient. Adopting a theoretical and molecular dynamics approach, we determine the Cassie–Baxter and Wenzel states of the droplets, investigate the efficiency of rugotaxis as a function of different parameters, and discuss additional effects, such as pinning. We find that shallow wrinkles characterised by small wavelength gradients, and moderate adhesion of the droplet to the substrate favour the rugotaxis motion with growing droplet size, when pinning is avoided. We also find that the driving force in rugotaxis is the gain in interfacial energy between the droplet and the substrate as the droplet enters regions of denser wrinkles (smaller wavelengths of the wrinkles).

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Height of a liquid drop on a wetting stripe

Cited by 4 publications

References 52 publications

Density Functional Theory Approach to Interpret Elastowetting of Hydrogels

Density Functional Theory Approach to Interpret Elastowetting of Hydrogels

Intrusion of liquids into liquid infused surfaces with nanoscale roughness

Rugotaxis: Droplet motion without external energy supply

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