Pinning forces of sliding drops at defects

Saal, Alexander; Straub, Benedikt B.; Butt, Hans Juergen; Berger, Rüdiger

doi:10.1209/0295-5075/ac7acf

Cited by 8 publications

(9 citation statements)

References 29 publications

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“…The drop length and width change significantly at the onset of sliding 41,42 and while interacting with topographic and chemical defects. 39,43,44 Rearranging eqn (1) and (4) allows us to omit drop width from the expression and provides an expression for the surface charge density:here all the parameters on the right hand side of the equation can be quantified using our in-house developed eDoFFI. The k is a numerical constant and is typically in the range of 0.7–1.…”

Section: Resultsmentioning

confidence: 99%

Slide electrification of drops at low velocities

Hinduja,

Butt,

Berger

2024

Soft Matter

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Section: Resultsmentioning

confidence: 99%

Slide electrification of drops at low velocities

Hinduja,

Butt,

Berger

2024

Soft Matter

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“…Several studies focused on the pinning forces resulting from a single defect, such as a stripe-like defect and a round defect . Here, the hydrophilic–hydrophobic junction has a significant impact on the sliding behavior of droplets.…”

Section: Resultsmentioning

confidence: 99%

Sliding Behavior of Droplets on a Tilted Substrate with a Chemical Step

Li,

Liu,

et al. 2023

Langmuir

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Controlling and predicting the motion of droplets on a heterogeneous substrate have received widespread attention. In this paper, we numerically simulate the droplet sliding through a “chemical step”, that is, different wetting properties at two sides of the step, on a tilted substrate by the multiphase lattice Boltzmann method (LBM). Three kinds of equilibrium statuses are reproduced by observing the deformation of the droplet and the velocities of the front contact line. This study shows the droplet obtains a driving force to break through the step by deformation in the initial stage that the droplet is blocked. The droplet spreads to two sides along the step when the front end is blocked and is stretched after the front end is passed over the step. The lengths of the lateral spreading and the longitudinal stretching and the time required to pass over the step depend on the strength of the step. In the sliding process, the kinetic energy is converted into surface energy as the droplet is blocked, and the gravitational potential energy is converted into surface and kinetic energy following the droplet passes over the step. If the droplet can slide through the step, the more strength in the step, the more the gravitational potential energy is converted, and the more the surface energy increases. When the strength of the step is small, unbalanced Young’s force hinders the contact line moving forward after the central part of the front end of the droplet breaks through the step. While the velocity of droplet sliding slows down with the increasing strength of the step, the unbalanced Young’s force pushes the contact line forward against the resistance. These observations throw insight into the dynamics of the droplets sliding on a heterogeneous surface, which may facilitate potential applications like microfluidics and liquid transportation.

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“…As substrates, 170 μm thick precision glass coverslips were used (Carl Roth no. 1.5H) . Water, ethanol, and acetone were used to clean the coverslips.…”

Section: Methodsmentioning

confidence: 99%

“…1.5H). 36 Water, ethanol, and acetone were used to clean the coverslips. To prepare topographic defects, we used photolithography (masks provided by DeltaMask).…”

Section: Methodsmentioning

confidence: 99%

Deep Learning to Analyze Sliding Drops

Shumaly

Darvish

et al. 2023

Langmuir

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State-of-the-art contact angle measurements usually involve image analysis of sessile drops. The drops are symmetric and images can be taken at high resolution. The analysis of videos of drops sliding down a tilted plate is hampered due to the low resolution of the cutout area where the drop is visible. The challenge is to analyze all video images automatically, while the drops are not symmetric anymore and contact angles change while sliding down the tilted plate. To increase the accuracy of contact angles, we present a 4-segment super-resolution optimized-fitting (4S-SROF) method. We developed a deep learning-based super-resolution model with an upscale ratio of 3; i.e., the trained model is able to enlarge drop images 9 times accurately (PSNR = 36.39). In addition, a systematic experiment using synthetic images was conducted to determine the best parameters for polynomial fitting of contact angles. Our method improved the accuracy by 21% for contact angles lower than 90°and by 33% for contact angles higher than 90°.

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Pinning forces of sliding drops at defects

Cited by 8 publications

References 29 publications

Slide electrification of drops at low velocities

Slide electrification of drops at low velocities

Sliding Behavior of Droplets on a Tilted Substrate with a Chemical Step

Deep Learning to Analyze Sliding Drops

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