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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.


Surface assembling evolution by rate-dependent interface interception.(a) Absent surface accumulation at low evaporation temperature. (b) A few isolated particle islands appear on surface when drying at relative high temperature (40 °C). As the evaporation rate is still slow, most islands disappeared at the late evaporation stage, leaving part of bare substrate. (c) With further temperature increasing (60 °C), particle islands arise soon and quickly integrate together, forming a continuous particle layer on the whole drop surface. (d) Real-time reflection spectra of the surface assembling in (c). The blue shift of surface color origins from the shrinkage of particle interspace when the drop surface varies from sphere cap to flat (inset in d). All the snapshots are captured on region about 1 mm at drop apex (inset in a). The scale bar, 150 μm in (a–c).
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f3: Surface assembling evolution by rate-dependent interface interception.(a) Absent surface accumulation at low evaporation temperature. (b) A few isolated particle islands appear on surface when drying at relative high temperature (40 °C). As the evaporation rate is still slow, most islands disappeared at the late evaporation stage, leaving part of bare substrate. (c) With further temperature increasing (60 °C), particle islands arise soon and quickly integrate together, forming a continuous particle layer on the whole drop surface. (d) Real-time reflection spectra of the surface assembling in (c). The blue shift of surface color origins from the shrinkage of particle interspace when the drop surface varies from sphere cap to flat (inset in d). All the snapshots are captured on region about 1 mm at drop apex (inset in a). The scale bar, 150 μm in (a–c).

Mentions: Snapshots of region at drop apex (Fig. 3a inset) confirm this surface capture phenomenon. No visible particles assemble on drop surface when drying at low temperature because of slow evaporation rate (Fig. 3a, 30 °C), instead most particles are transported to contact line (Mov. S1). As the evaporation temperature rising, the air-liquid interface descends sharply and a few particle islands come into view (Fig. 3b). However, the interface-descending rate is still too slow to form larger domains, much less incorporate the isolate islands together to form a continuous particle layer. In addition, due to the insufficient particle supply and spontaneous desorption from high concentration near surface to bulk, the formed islands disappear at later stage of evaporation because of the weak interaction between isotropic spherical particles and air-liquid interface435 fail to fix the captured particles firmly. Therefore, coffee-ring effect still dominates the particle redistribution process. However, as the temperature rises further, interface-descending rate becomes large enough to form a continuous particle layer (Fig. 3c). The interface capture effect is so strong that the formed islands integrate quickly and cover the whole drop surface. This quasi-solid layer retains until the end of drying and directly deposits at center.


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

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

Surface assembling evolution by rate-dependent interface interception.(a) Absent surface accumulation at low evaporation temperature. (b) A few isolated particle islands appear on surface when drying at relative high temperature (40 °C). As the evaporation rate is still slow, most islands disappeared at the late evaporation stage, leaving part of bare substrate. (c) With further temperature increasing (60 °C), particle islands arise soon and quickly integrate together, forming a continuous particle layer on the whole drop surface. (d) Real-time reflection spectra of the surface assembling in (c). The blue shift of surface color origins from the shrinkage of particle interspace when the drop surface varies from sphere cap to flat (inset in d). All the snapshots are captured on region about 1 mm at drop apex (inset in a). The scale bar, 150 μm in (a–c).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Surface assembling evolution by rate-dependent interface interception.(a) Absent surface accumulation at low evaporation temperature. (b) A few isolated particle islands appear on surface when drying at relative high temperature (40 °C). As the evaporation rate is still slow, most islands disappeared at the late evaporation stage, leaving part of bare substrate. (c) With further temperature increasing (60 °C), particle islands arise soon and quickly integrate together, forming a continuous particle layer on the whole drop surface. (d) Real-time reflection spectra of the surface assembling in (c). The blue shift of surface color origins from the shrinkage of particle interspace when the drop surface varies from sphere cap to flat (inset in d). All the snapshots are captured on region about 1 mm at drop apex (inset in a). The scale bar, 150 μm in (a–c).
Mentions: Snapshots of region at drop apex (Fig. 3a inset) confirm this surface capture phenomenon. No visible particles assemble on drop surface when drying at low temperature because of slow evaporation rate (Fig. 3a, 30 °C), instead most particles are transported to contact line (Mov. S1). As the evaporation temperature rising, the air-liquid interface descends sharply and a few particle islands come into view (Fig. 3b). However, the interface-descending rate is still too slow to form larger domains, much less incorporate the isolate islands together to form a continuous particle layer. In addition, due to the insufficient particle supply and spontaneous desorption from high concentration near surface to bulk, the formed islands disappear at later stage of evaporation because of the weak interaction between isotropic spherical particles and air-liquid interface435 fail to fix the captured particles firmly. Therefore, coffee-ring effect still dominates the particle redistribution process. However, as the temperature rises further, interface-descending rate becomes large enough to form a continuous particle layer (Fig. 3c). The interface capture effect is so strong that the formed islands integrate quickly and cover the whole drop surface. This quasi-solid layer retains until the end of drying and directly deposits at center.

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.