Unified framework for mapping shape and stability of pendant drops including the effect of contact angle hysteresis

Kumar, Alok; Gunjan, Madhu Ranjan; Jakhar, Karan; Thakur, Atul; Raj, Rishi

doi:10.1016/j.colsurfa.2020.124619

Cited by 12 publications

(5 citation statements)

References 43 publications

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“…One hydrophobic (θc=100°) and one hydrophilic (θc=50°) substrates are considered, and pendant, sessile and spherical-cap shaped drops are assumed to evaporate under both modes. Figure 3 shows the shape and the stability map (see [12] for a clear explanation) of sessile and pendant drops, respectively, and the paths followed by drops on hydrophobic and hydrophilic substrates are reported for both evaporation modes (thick black lines).…”

Section: Resultsmentioning

confidence: 99%

“…Differently from sessile drops, pendant drops become unstable when their size increases, falling from the substrate, a fact that limits the size of the drops. The shape of a drop in contact with a solid surface has been deeply studied since the pioneering work of [11] and a copious literature on this subject is available (see for example [12] and the cited literature therein).…”

Section: Introductionmentioning

confidence: 99%

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Gravity induced shape effects on the time-dependent evaporation of pendant drops

Tonini,

Cossali

2024

J. Phys.: Conf. Ser.

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The paper presents a method to model the time-dependent evaporation of pendant drops taking into account the effect of drop deformation induced by gravity. The model is based on the solution to the time-dependent drop mass and energy conservation equations, where the mass and energy fluxes through the gas mixture are numerically evaluated for a range of Bond numbers and contact angles. The evaporation characteristics of pendant and sessile drops on hydrophobic and hydrophilic substrates are compared in terms of evaporation times and evaporative cooling, for both constant contact angle and constant contact radius modes.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gravity induced shape effects on the time-dependent evaporation of pendant drops

Tonini,

Cossali

2024

J. Phys.: Conf. Ser.

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“…It is evident from the snapshots in Figure b,c that pendant droplet transportation on the MRSS occurs smoothly using the moving magnetic field. It is worth mentioning that a pendant droplet remains stable up to a certain maximum volume, beyond which it becomes unstable and detaches from the surface. , Thus, magnet-assisted transportation of pendant droplets will have important implications for applications related to no-loss droplet transportation, droplet coalescence, detachment, and microreactors. The experimental video corresponding to the manipulation of the pendant drops can be found in the Supporting Information (Movie S2).…”

Section: Results and Discussionmentioning

confidence: 99%

Directional Manipulation of Drops and Solids on a Magneto-Responsive Slippery Surface

Banerjee,

Gunjan,

Mitra

2024

Langmuir

Self Cite

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The cloaking of the droplet and solid spheres by a thin ferrofluid layer forms a ferrofluid-wetting ridge, enabling the magnet-assisted directional manipulation of droplets and solid spheres on the magneto-responsive slippery surface. Understanding the interplay of various forces governing motion unravels the manipulation mechanism. The transportation characteristics of droplets and solid spheres on such surfaces enable their controlled manipulation in multiple applications. Here, we prepare magnetoresponsive slippery surfaces by using superhydrophobic coatings on glass slides, creating a porous network and impregnating them with ferrofluid. Using a permanent magnet (and its translation) in the proximity of these surfaces, we manipulate the motion of liquid drops and solid spheres. Upon dispensing the droplet on the magneto-responsive slippery surface, the droplet is cloaked by a thin ferrofluid layer and forms a ferrofluid wetting ridge. Incorporating the magnetic field creates a magnetic-nanoparticle-rich zone surrounding the ferrofluid ridge. Thereafter, the motion of the magnet gives rise to the movement of the droplet. We found that the interplay of the magnetic force and viscous drag leads to the magnetic manipulation of droplets in a controlled fashion up to a certain magnet speed. Increasing the magnet speed further results in the uncontrolled motion of the droplet, where the droplet cannot follow the magnet trajectory. Moreover, we delineate multifunctional droplet manipulations, such as trapping, pendant droplet manipulation, coalescence, and microchemical reactions, which have wide engineering applications.

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“…Silicon oil (10 mPa•s at 20 ℃) and alcohol (99.8% pure) were used because they could completely wet the nozzle, making the experiments more convenient without considering the effect of the contact angle. 16,20,21 A high-speed camera (Phantom V2512, USA) with a telephoto lens was used to capture the detailed dynamics of the droplet formation. A light-emitting diode (LED) lamp was used as the background light.…”

Section: Methodsmentioning

confidence: 99%

Droplet formation on an inclined needle

Wang

Lin

et al. 2022

Preprint

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An experimental study of droplet formation on an inclined stainless-steel needle is presented. The detailed dynamics of the droplet formation is captured with the help of a high-speed camera. Droplet diameter is found to depend on both the needle diameter and the tilt angle. For the vertical condition, the droplet diameter increases with the needle diameter. A semiempirical model is built to elucidate this trend based on the force balance between gravity, capillary, and Laplace forces. For the inclined condition, the droplet diameter increases with the tilt angle. Effect of the tilt angle on the droplet diameter is attributed to the variation of the capillary force between the droplet and the inclined needle. Variation of the tilt angle plays a similar role to the variation of the needle diameter, which can be used to adjust the droplet diameter in practice.

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Unified framework for mapping shape and stability of pendant drops including the effect of contact angle hysteresis

Cited by 12 publications

References 43 publications

Gravity induced shape effects on the time-dependent evaporation of pendant drops

Gravity induced shape effects on the time-dependent evaporation of pendant drops

Directional Manipulation of Drops and Solids on a Magneto-Responsive Slippery Surface

Droplet formation on an inclined needle

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