Surfactant-Induced Marangoni Eddies Alter the Coffee-Rings of Evaporating Colloidal Drops

Still, Tim; Yunker, Peter; Yodh, Arjun G.

doi:10.1021/la204928m

Cited by 402 publications

(448 citation statements)

References 27 publications

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“…In the case of the experiment employed aqueous suspensions of colloidal polystyrene particles with diameter d= =1330 nm, nearly all particles were deposited in a thin ring and very few particles occupied the center of drop (Still et al, 2012). At the present stage, we are unsure to conclude whether these particles placed at center of droplet are the soot particles (and/or background particles) fed into a CCN chamber.…”

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confidence: 88%

“…known as the "coffee-ring" effect, is formed when the drop edges are pinned and subsequent radial capillary flows from the drop center to its edge carry suspended or dissolved solutes to the perimeter (Still et al, 2012). In the case of the experiment employed aqueous suspensions of colloidal polystyrene particles with diameter d= =1330 nm, nearly all particles were deposited in a thin ring and very few particles occupied the center of drop (Still et al, 2012).…”

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confidence: 99%

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Preliminary Study on the Cloud Condensation Nuclei (CCN) Activation of Soot Particles by a Laboratory-scale Model Experiments

Ma¹,

Kim²

2014

Asian J. Atmos. Environ

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To visually and chemically verify the rainout of soot particles, a model experiment was carried out with the cylindrical chamber (0.2 m (D) and 4 m (H)) installing a cloud drop generator, a hydrotherometer, a particle counter, a drop collector, a diffusing drier, and an artificial soot particle distributer. The processes of the model experiment were as follows; generating artificial cloud droplets (major drop size : 12-14 μm) until supersaturation reach at 0.52%-nebulizing of soot particles (JIS Z 8901) with an average size of 0.5 μm-counting cloud condensation nuclei (CCN) particles and droplets by OPC and the fixation method (Ma et al., 2011;Carter and Hasegawa, 1975), respectively -collecting of individual cloud drops -observation of individual cloud drops by SEMchemical identifying of residual particle in each individual droplet by SEM-EDX. After 10 minutes of the completion of soot particle inject, the number concentrations of PM of all sizes (¤0.3 μm) dramatically decreased. The time required to return to the initial conditions, i.e., the time needed to CCN activation for the fed soot particles was about 40 minutes for the PM sized from 0.3-2.0 μm. The EDX spectra of residual particles left at the center of individual droplet after evaporation suggest that the soot particles seeded into our experimental chamber obviously acted as CCN. The coexistence of soot and mineral particle in single droplet was probably due to the coalescence of droplets (i.e., two droplets embodying different particles (in here, soot and background mineral particles) were coalesced) or the particle capture by a droplet in our CCN chamber.

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confidence: 88%

mentioning

confidence: 99%

Preliminary Study on the Cloud Condensation Nuclei (CCN) Activation of Soot Particles by a Laboratory-scale Model Experiments

Ma¹,

Kim²

2014

Asian J. Atmos. Environ

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“…One method is to change the surface tension using cosolvents [6] or polymers in solution [7] to promote an opposing Marangoni flow. [8] Yunker considered the influence of particle shape on coffee ring formation and predicted that it is suppressed with high aspect ratio particles. [9] However, Dugyala reported a clear ring after drying drops containing rod-like colloids with high aspect ratios; coffee rings have also been reported after the drying of inks containing carbon nanotubes [10] and graphene [11][12][13] contradicting Yunker's model.…”

Section: Inkjet Printingmentioning

confidence: 99%

Controlling Coffee Ring Formation during Drying of Inkjet Printed 2D Inks

Derby

2017

Adv Materials Inter

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There have been several reports of the deposition of graphene dispersions and other 2D materials using inkjet printing. [12,[14][15][16][17][18] Generally, 2D material inks show similar drying behavior to inks made from nanoparticles or nanotubes, i.e. under appropriate drying conditions they show a clear coffee ring with the 2D flakes or 1D tubes arranged at the contact line forming a characteristic ringlike structure. [14,15] Ring formation can be suppressed, for example, by using two solvents [16,17] or adding surfactant and a high boiling point solvent. Recent work by Kim et al. identified both an effect of size and an effect of temperature on the transition to a coffee ring during the drying of suspensions of graphene oxide (GO), [19] with higher drying temperatures suppressing coffee ring formation and a slightly lower critical temperature for ring suppression with inks containing larger GO flakes.Here, we further study the influence of flake size, substrate temperature, and drop size on the morphology of dried droplets of a GO ink. GO is an appropriate model ink because of its ease of dispersal in water and that it is possible to make inks with a wide range of flake sizes showing a common mean flake thickness with little variance. [20] The critical flake size for ring/no ring transition decreases as the substrate (drying) temperature increases. A decrease in the critical flake size also occurs when smaller drop diameters were used. We show that this behavior is governed by hysteresis between the advancing and receding contact angle caused by contact line pinning from heterogeneities in the surface energy or profile (roughness). [21,22] At the onset of drying, the diameter of the drop does not change but the contact angle reduces. The contact line becomes pinned if there is sufficient deposition of solute at the contact line to prevent detachment once the receding contact angle for the substrate is reached. [23] The onset of a coffee ring during drying drops of GO inks is consistent with a model for contact line pinning that compares characteristic time constants for flake aggregation and for the transition from the equilibrium to the receding contact angle.Inkjet printing was used to provide single sessile drops on Si/SiO 2 substrates from aqueous inks containing GO flakes of different sizes. Figure 1 shows the particle size distribution for the eight inks (GO-0-GO-7) used in this study; the mean particle size ranges from 0.68 to 35.9 µm. Sample scanning electron microscopy (SEM) images of the flakes and atomic force microscopy (AFM) height profiles are presented in the Supporting Information showing that the majority of the flakes The morphology of drops of graphene oxide (GO) inks produced by inkjet printing shows a distinctive coffee ring after drying when the mean diameter of the GO is below a critical size. Inks with larger diameter flakes do not show a coffee ring and the transition mean flake diameter decreases as the substrate temperature increases and when the printed drop size decreases. This be...

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“…This coffee-ring effect (reviewed in [3,4]) will limit the application of droplet evaporation in many fields such as printing, biology and complex assembly. To obtain a uniform evaporation stain, a lot of methods have been proposed such as by changing the shape of microparticles [5], using electrowetting [6,7], adding surfactants [8] or hydrosoluble polymers [9], promoting particle adsorption and long-range interaction [10], changing the evaporation environment [11] and using contact angle hysteresis [12].…”

Section: Introductionmentioning

confidence: 99%

Quasi-static motion of microparticles at the depinning contact line of an evaporating droplet on PDMS surface

Xia

Zheng

et al. 2017

Sci. China Phys. Mech. Astron.

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In this paper, evaporation of sessile water droplets containing fluorescent polystyrene (PS) microparticles on polydimethylsiloxane (PDMS) surfaces with different curing ratios was studied experimentally using laser confocal microscopy. At the beginning, there were some microparticles located at the contact line and some microparticles moved towards the line. Due to contact angle hysteresis, at first both the contact line and the microparticles were pinned. With the depinning contact line, the microparticles moved together spontaneously. Using the software ImageJ, the location of contact lines at different time were acquired and the circle centers and radii of the contact lines were obtained via the least square method. Then the average distance of two neighbor contact lines at a certain time interval was obtained to characterize the motion of the contact line. Fitting the distance-time curve at the depinning contact line stage with polynomials and differentiating the polynomials with time, we obtained the velocity and acceleration of both the contact line and the microparticles located at the line. The velocity and the maximum acceleration were, respectively, of the orders of 1 µm/s and 20-200 nm/s 2 , indicating that the motion of the microparticles located at the depinning contact line was quasi-static. Finally, we presented a theoretical model to describe the quasi-static process, which may help in understanding both self-pinning and depinning of microparticles.

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Surfactant-Induced Marangoni Eddies Alter the Coffee-Rings of Evaporating Colloidal Drops

Cited by 402 publications

References 27 publications

Preliminary Study on the Cloud Condensation Nuclei (CCN) Activation of Soot Particles by a Laboratory-scale Model Experiments

Preliminary Study on the Cloud Condensation Nuclei (CCN) Activation of Soot Particles by a Laboratory-scale Model Experiments

Controlling Coffee Ring Formation during Drying of Inkjet Printed 2D Inks

Quasi-static motion of microparticles at the depinning contact line of an evaporating droplet on PDMS surface

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