Modeling Evaporation and Particle Assembly in Colloidal Droplets

Zhao, Menghua

doi:10.1021/acs.langmuir.7b00284

Cited by 31 publications

(27 citation statements)

References 60 publications

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“…A large number of these applications deal with colloidal drops that leave behind a residue once they completely dry out. Common examples include ink-jet printing 1–6 and fabricating ordered microelectronic structures via evaporative self-assembly 7–15 , where the time it takes for the deposit to form is a key design parameter.…”

Section: Introductionmentioning

confidence: 99%

Evaporation of a sessile droplet on a slope

Timm

Dehdashti

Darban

et al. 2019

Sci Rep

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We theoretically examine the drying of a stationary liquid droplet on an inclined surface. Both analytical and numerical approaches are considered, while assuming that the evaporation results from the purely diffusive transport of liquid vapor and that the contact line is a pinned circle. For the purposes of the analytical calculations, we suppose that the effect of gravity relative to the surface tension is weak, i.e. the Bond number (Bo) is small. Then, we express the shape of the drop and the vapor concentration field as perturbation expansions in terms of Bo. When the Bond number is zero, the droplet is unperturbed by the effect of gravity and takes the form of a spherical cap, for which the vapor concentration field is already known. Here, the Young-Laplace equation is solved analytically to calculate the first-order correction to the shape of the drop. Knowing the first-order perturbation to the drop geometry and the zeroth-order distribution of vapor concentration, we obtain the leading-order contribution of gravity to the rate of droplet evaporation by utilizing Green’s second identity. The analytical results are supplemented by numerical calculations, where the droplet shape is first determined by minimizing the Helmholtz free energy and then the evaporation rate is computed by solving Laplace’s equation for the vapor concentration field via a finite-volume method. Perhaps counter-intuitively, we find that even when the droplet deforms noticeably under the influence of gravity, the rate of evaporation remains almost unchanged, as if no gravitational effect is present. Furthermore, comparison between analytical and numerical calculations reveals that considering only the leading-order corrections to the shape of the droplet and vapor concentration distribution provides estimates that are valid well beyond their intended limit of very small Bo.

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Section: Introductionmentioning

confidence: 99%

Evaporation of a sessile droplet on a slope

Timm

Dehdashti

Darban

et al. 2019

Sci Rep

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“…Many of these issues are addressed by using lattice Boltzmann (LB) methods, 16 which model the solvent as a continuum, but the suspended particles are treated explicitly -see for example the LB models for the evaporation of droplets containing suspended particles described in Refs. 17,18. Fully microscopic models based on molecular dynamics (MD) computer simulations, such as those described in Refs.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Density Functional Theory for the Evaporation of Droplets of Nanoparticle Suspension

2017

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We develop a lattice gas model for the drying of droplets of a nanoparticle suspension on a planar surface, using dynamical density functional theory (DDFT) to describe the time evolution of the solvent and nanoparticle density profiles. The DDFT assumes a diffusive dynamics but does not include the advective hydrodynamics of the solvent, so the model is relevant to highly viscous or near to equilibrium systems. Nonetheless, we see an equivalent of the coffee-ring stain effect, but in the present model it occurs for thermodynamic rather the fluid-mechanical reasons. The model incorporates the effect of phase separation and vertical density variations within the droplet and the consequence of these on the nanoparticle deposition pattern on the surface. We show how to include the effect of slip or no-slip at the surface and how this is related to the receding contact angle. We also determine how the equilibrium contact angle depends on the microscopic interaction parameters.

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“…Recently, a two-way coupled LB and Langevin equation approach was developed to capture the Brownian motion of NPs and polymer suspensions in complex flows (Liu et al, 2019). Further, to explore the evaporation-driven assembly of NPs in a drying sessile droplet, Zhao and Yong (2017) developed a hybrid LB-Brownian model and identified the distinct dynamics between the interface-bound and bulk-dispersed NPs.…”

Section: Introductionmentioning

confidence: 99%

Evaporation-driven nanoparticles motion and deposition on a textured surface in the inkjet process

Zhang

Wang

2021

Engineering Applications of Computational Fluid Mechanics

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The evaporation-driven motion and deposition dynamics of nanoparticles (NPs) play significant roles in inkjet-printed structures such as the finger electrodes of solar cells. The objective of the present work is to reveal the mechanisms of NPs motion and distribution on a textured surface in the multidroplets impact, coalescence and evaporation process. However, the complex interplay among NPs, host fluids and textured medium presents great challenges to numerical modeling. In this paper, a hybrid 3D lattice Boltzmann (LB) model coupled with the Langevin equation (LE) model is presented to handle the multi-droplets impact, coalescence, evaporation and NPs motion dynamics. In the droplet evaporation process, two patterns of NPs deposition rate are first identified at the time of maximum spreading width. For simultaneous and successive impact modes, three peaks of deposited NPs are formed adjacent to the droplet centers after drying out. And the quantities of deposited NPs adjacent to the collision region are increased due to enhanced NPs mixing in successive impacts mode. Detailed figures of NPs motion and deposition on a textured surface are offered that provide in-depth insights beneficial for optimizing the inkjet printing process.

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Modeling Evaporation and Particle Assembly in Colloidal Droplets

Cited by 31 publications

References 60 publications

Evaporation of a sessile droplet on a slope

Evaporation of a sessile droplet on a slope

Dynamical Density Functional Theory for the Evaporation of Droplets of Nanoparticle Suspension

Evaporation-driven nanoparticles motion and deposition on a textured surface in the inkjet process

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