Viscous Force Retards Initial Droplet Spreading

Shi, Lichun; Liu, Yang; Lu, Hongyu; Meng, Yonggang; Hu, Guoqing; Tian, Yu

doi:10.1021/acs.jpcc.7b06124

Cited by 15 publications

(4 citation statements)

References 33 publications

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“…While the spreading of spherical droplets has been extensively investigated via experiments, ,, theory, − and computational methods, , the spreading of filaments has received little attention. One exception is the work by Starov et al, which developed a theoretical model for the spreading of a 2D symmetric cylindrical filament in the capillary and gravitational spreading limits.…”

Section: Introductionmentioning

confidence: 99%

Predicting the Dynamics and Steady-State Shape of Cylindrical Newtonian Filaments on Solid Substrates

2023

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The spreading of liquid filaments on solid surfaces is of paramount importance to a wide range of applications including ink-jet printing, coating, and direct ink writing (DIW). However, there is a considerable lack of experimental, numerical, and theoretical studies on the spreading of filaments on solid substrates. In this work, we studied the dynamics of spreading of Newtonian filaments via experiment, numerical simulations, and theoretical analysis. More specifically, we used a novel experimental setup to validate a 2D moving mesh computational fluid dynamics (CFD) model. The CFD model is used to determine the effect of processing and fluid parameters on the dynamics of filament spreading. We experimentally showed that for a Newtonian filament, the same spreading dynamics and final shape are obtained when the initial radius is constant, independent of the magnitude in printing parameters. In other words, the only important parameter on the spreading of filaments is the initial filament radius. Using a numerical model, we showed that the initial filament radius manifests itself in two important dimensionless parameters, Bond number, Bo, and viscous timescale, τμ. Furthermore, the results clearly show that the dynamics of spreading are governed by the static advancing contact angle, θs. These three parameters determine a master spreading curve that can be used to predict the spreading of cylindrical filaments on flat substrates. Finally, we developed a theoretical model that was parameterized using experimental data to correlate the steady-state shape of filaments with Bo and θs. These results are particularly applicable for predicting and controlling the dynamics of filaments in DIW and other extrusion-based processes.

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Section: Introductionmentioning

confidence: 99%

Predicting the Dynamics and Steady-State Shape of Cylindrical Newtonian Filaments on Solid Substrates

2023

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“…Figure 5b shows the droplet shape and the droplet resistance at different times. A high-speed camera (NAC HX-6) with a frame rate of 10 000 frames/s was used to capture the spreading of the droplet (initial radius R ≈ 1.12 mm) 37 and to obtain the spreading radius. As the spreading radius increased, the droplet began to deform at the top and propagated rapidly to the bottom.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Measuring the Adhesion Force and the Spreading Radius between Droplets and a Solid Surface during Short-Time Spreading

et al. 2023

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When a droplet contacts a solid surface, the liquid spreads over the solid surface to minimize the total surface energy. This phenomenon is widespread in industrial production and nature, so research on droplet spreading is of great significance. Here, the adhesion force and the spreading radius during droplet spreading can be quantified using a highly sensitive photoelectric method. It is possible to study droplet spreading from two dimensions at the microscale. The adhesion force is measured by an optical lever, and the spreading radius is measured by an ultrafast electrical method. The measurement method allows the force resolution and the space−time resolution to reach the nanonewton lever and the nanosecond lever, respectively. We obtain the maximum spreading radius and the maximum adhesion force during short-time spreading through our technique. Moreover, we numerically simulate the droplet spreading process through the lattice Boltzmann solver and confirm the observed results. This study provides a new experimental technique for studying droplet spreading dynamics from multiple perspectives, which can deepen our understanding of droplet spreading and provide guidance for the development of new techniques.

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“…In general, the larger the value of

, the longer it takes to reach the equilibrium state of spreading, and vice versa. These indicated that the early spreading stage, t < 10 ms, of oil droplets was quite short, which was dominated by the inertial force [ 26 , 43 , 47 , 48 ]. In the intermediate stage of spreading (10 ms ≤ t < 100 ms), the temporal evolution of dynamic contact angle could be well described by a simple scaling law of

, and the spreading exponent (−0.28) was close to −0.3 (

) obtained based on the HD model, which suggested that the spreading of the oleic acid droplet on the Teflon in air during the intermediate spreading process was dominated by the viscous dissipation due to viscous flow in the core of the droplet [ 27 , 30 ].…”

Section: Resultsmentioning

confidence: 99%

“…Starov et al [ 24 ] and Lee et al [ 25 ] considered the spreading behavior of surfactant solution droplets over various substrates from both theoretical and experimental points of view, and suggested that the transfer of surfactant molecules from the water droplet onto the hydrophobic surface changed the wetting characteristics in front of the droplet on the TPCL. Shi et al [ 26 ] performed an interesting experiment to study the spreading behavior of a conducted droplet on two glass plates coated with a conductive indium tin oxide (ITO) thin film within several milliseconds, and found that the spreading process in this time scale could be separated into two stages: a fast-inertial stage and a subsequent slow-viscous stage.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study on the Spreading Behavior of Oil Droplets over Teflon Substrates in Different Media Environments

Wang

Cao

2022

Polymers

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This paper comparatively investigated the spreading process of an oil droplet on the surface of highly hydrophobic solid (Teflon) in air and water media using a high-speed imaging technology, and analyzed their differences in spreading behavior from the perspective of empirical relations and energy conservation. Furthermore, the classical HD and MKT wetting models were applied to describe the oil droplet spreading dynamics to reveal the spreading mechanism of oil droplets on the Teflon in different media environments. Results showed that the entire spreading process of oil droplets on Teflon in air could be separated into three stages: the early linear fast spreading stage following θ(t)=θ0+kt , the intermediate exponential slow spreading stage obeying θ(t)=bt−3α, and the late spreading stage described by θ(t)=θeq+a×exp(−t/T). However, the dynamics behavior of dynamic contact angle during the oil droplet spreading on Teflon in water could be well described by these expressions, θ(t)=θ0+kt and θ(t)=θeq+a×exp(−t/T). Clearly, a significant difference in the oil droplet spreading behavior in air and water media was found, and the absence of the intermediate exponential spreading stage in the oil–water–Teflon system could be attributed to the difference in the dissipated energy of the system because the dissipation energy in the oil–water–solid system included not only the viscous dissipation energy of the boundary layer of oil droplet, but also that of the surrounding water which was not included in the dissipation energy of the oil–air–solid system. Moreover, the quantitative analysis of wetting models suggested that the MKT model could reasonably describe the late spreading dynamics of oil droplets (low TPCL velocities), while the HD model may be more suitable for describing the oil droplet spreading dynamics at the early and intermediate spreading stages (high TPCL velocities).

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Viscous Force Retards Initial Droplet Spreading

Cited by 15 publications

References 33 publications

Predicting the Dynamics and Steady-State Shape of Cylindrical Newtonian Filaments on Solid Substrates

Predicting the Dynamics and Steady-State Shape of Cylindrical Newtonian Filaments on Solid Substrates

Measuring the Adhesion Force and the Spreading Radius between Droplets and a Solid Surface during Short-Time Spreading

Comparative Study on the Spreading Behavior of Oil Droplets over Teflon Substrates in Different Media Environments

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