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Rate-dependent interface capture beyond the coffee-ring effect.

Li Y, Yang Q, Li M, Song Y - Sci Rep (2016)

Bottom Line: The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication.Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly.As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences (ICCAS), Beijing Engineering Research Center of Nanomaterials for Green Printing Technology, Beijing National Laboratory for Molecular Sciences (BNLMS), Beijing, 100190, P. R. China.

ABSTRACT
The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication. Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly. As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition. This simple, robust drying regime will provide a versatile strategy to control the droplet deposition morphology, and a novel direction of interface assembling for fabricating superlattices and high quality photonic crystal patterns.

No MeSH data available.


Related in: MedlinePlus

The suppressed coffee ring effect with increasing evaporation rate.(a,b) Images and morphology profiles of the final deposition by drying at room temperature (a, T = 25 °C) and high temperature (b, T = 75 °C) with constant humidity (50%). Most of the particles deposit at drop edge forming ring-like fashion when drying at slow evaporation rate. In contrast, a uniform deposition is formed with only a tiny part of the particle deposited on edge when drying at high temperature. (c) The cross section area proportion (S/Stotal) of ring region decreases as that of the center region arises when the evaporation temperature rises, indicating the gradually suppression of coffee-ring effect. (d) Highly ordered assembling of the monodispersed particles. The scale bar, 0.5 mm in (a,b), 1 μm in (d).
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f1: The suppressed coffee ring effect with increasing evaporation rate.(a,b) Images and morphology profiles of the final deposition by drying at room temperature (a, T = 25 °C) and high temperature (b, T = 75 °C) with constant humidity (50%). Most of the particles deposit at drop edge forming ring-like fashion when drying at slow evaporation rate. In contrast, a uniform deposition is formed with only a tiny part of the particle deposited on edge when drying at high temperature. (c) The cross section area proportion (S/Stotal) of ring region decreases as that of the center region arises when the evaporation temperature rises, indicating the gradually suppression of coffee-ring effect. (d) Highly ordered assembling of the monodispersed particles. The scale bar, 0.5 mm in (a,b), 1 μm in (d).

Mentions: The evaporation of solvent brings about not only the concentration of solute, but also the spatial redistribution of the dispersed phase123456. Drying of droplet is actually a complex, non-equilibrium and difficult-to-control process4, despite the controlling the deposition morphology of droplet has significant influence on printing78, biology pattern91011 self-assembling812 and other solution-based devices fabrication13141516. When a drop of coffee dries on a substrate, it often leaves a ring-like stain, known as the coffee-ring effect1. This ubiquitous phenomenon appears when the drop contact line remains pinned during the drying process; the suspended particles tend to accumulate at the drop edge for capillary outflow to replenish the local rapid solvent loss. Further studies on this nonuniform redistribution process indicate that inner flows, including capillary flow2 and Marangoni flow31117, dynamics of the three-phase contact line678131819, and particle-particle/particle-interface interaction4202122 will influence the final particle distribution. However, to study the initial mechanism of a drying droplet, much of the physics of the coffee-ring effect is demonstrated by drying the aqueous droplet in an open space at room temperature. In this condition, the distinct evaporation difference between drop edge and drop center is hard to avoid, droplet usually dries at relatively slow evaporation rate that most of the suspended particles are transported to drop edge by the strong capillary outflow (Fig. 1a).


Rate-dependent interface capture beyond the coffee-ring effect.

Li Y, Yang Q, Li M, Song Y - Sci Rep (2016)

The suppressed coffee ring effect with increasing evaporation rate.(a,b) Images and morphology profiles of the final deposition by drying at room temperature (a, T = 25 °C) and high temperature (b, T = 75 °C) with constant humidity (50%). Most of the particles deposit at drop edge forming ring-like fashion when drying at slow evaporation rate. In contrast, a uniform deposition is formed with only a tiny part of the particle deposited on edge when drying at high temperature. (c) The cross section area proportion (S/Stotal) of ring region decreases as that of the center region arises when the evaporation temperature rises, indicating the gradually suppression of coffee-ring effect. (d) Highly ordered assembling of the monodispersed particles. The scale bar, 0.5 mm in (a,b), 1 μm in (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835725&req=5

f1: The suppressed coffee ring effect with increasing evaporation rate.(a,b) Images and morphology profiles of the final deposition by drying at room temperature (a, T = 25 °C) and high temperature (b, T = 75 °C) with constant humidity (50%). Most of the particles deposit at drop edge forming ring-like fashion when drying at slow evaporation rate. In contrast, a uniform deposition is formed with only a tiny part of the particle deposited on edge when drying at high temperature. (c) The cross section area proportion (S/Stotal) of ring region decreases as that of the center region arises when the evaporation temperature rises, indicating the gradually suppression of coffee-ring effect. (d) Highly ordered assembling of the monodispersed particles. The scale bar, 0.5 mm in (a,b), 1 μm in (d).
Mentions: The evaporation of solvent brings about not only the concentration of solute, but also the spatial redistribution of the dispersed phase123456. Drying of droplet is actually a complex, non-equilibrium and difficult-to-control process4, despite the controlling the deposition morphology of droplet has significant influence on printing78, biology pattern91011 self-assembling812 and other solution-based devices fabrication13141516. When a drop of coffee dries on a substrate, it often leaves a ring-like stain, known as the coffee-ring effect1. This ubiquitous phenomenon appears when the drop contact line remains pinned during the drying process; the suspended particles tend to accumulate at the drop edge for capillary outflow to replenish the local rapid solvent loss. Further studies on this nonuniform redistribution process indicate that inner flows, including capillary flow2 and Marangoni flow31117, dynamics of the three-phase contact line678131819, and particle-particle/particle-interface interaction4202122 will influence the final particle distribution. However, to study the initial mechanism of a drying droplet, much of the physics of the coffee-ring effect is demonstrated by drying the aqueous droplet in an open space at room temperature. In this condition, the distinct evaporation difference between drop edge and drop center is hard to avoid, droplet usually dries at relatively slow evaporation rate that most of the suspended particles are transported to drop edge by the strong capillary outflow (Fig. 1a).

Bottom Line: The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication.Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly.As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences (ICCAS), Beijing Engineering Research Center of Nanomaterials for Green Printing Technology, Beijing National Laboratory for Molecular Sciences (BNLMS), Beijing, 100190, P. R. China.

ABSTRACT
The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication. Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly. As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition. This simple, robust drying regime will provide a versatile strategy to control the droplet deposition morphology, and a novel direction of interface assembling for fabricating superlattices and high quality photonic crystal patterns.

No MeSH data available.


Related in: MedlinePlus