From multi-ring to spider web and radial spoke: competition between the receding contact line and particle deposition in a drying colloidal drop

Yang, Xiulun; Sun, Ying

doi:10.1039/c4sm00497c

Cited by 32 publications

(40 citation statements)

References 37 publications

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“…During a drying step, most CQDs in the droplet accumulated at the center, creating a micrometer‐thick island, whereas only small amounts of CQDs were deposited in other areas. This center‐focused island‐like pattern away from the periphery of droplet is consistent with the previous reports which occurs when the contact line of droplet is mobile. We hypothesized that this center‐focused deposition comes from slow drying process, giving CQDs enough time to migrate with solvent rather than be deposited on substrate (Figure b).…”

supporting

confidence: 92%

Tuning Solute‐Redistribution Dynamics for Scalable Fabrication of Colloidal Quantum‐Dot Optoelectronics

et al. 2019

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Solution-processed colloidal quantum dots (CQDs) are a promising class of semiconducting materials in view of their tunable optical and electronic properties through the quantum size effect. [1][2][3][4][5] They have been used to fabricate nextgeneration thin-film optoelectronic devices including light-emitting diodes, [6] photodetectors, [7] and solar cells. [8][9][10][11][12][13] For example, recent perovskite quantum dotbased light-emitting devices showed an external quantum efficiency exceeding 20%. [14][15][16][17] Solar cells based on lead chalcogenide CQDs have demonstrated power conversion efficiencies (PCE) of 11.3% [18] and a stabilized output over 150 days when stored in air even without encapsulation, [19] making them candidates for low-cost, stable, and scalable next-generation photovoltaics.While the performance of CQD solar cells has improved rapidly, the fabrication process is still limited to labscale, batch-processing methods, mainly due to reliance on a complex and wasteful multistep layer-by-layer (LbL) ligand exchange method, [20] which to date has been most commonly combined with repeated spin-casting deposition. To overcome this limitation, a solution-phase ligand exchange method was recently developed to realize the single-step fabrication of CQD films. [21][22][23] In particular, inorganic anions such as metal chalcogenide complexes, halides, and metal-free ions (S 2− , OH − , SCN − , etc.) have been successfully applied as capping ligands and improved the colloidal dispersion. However, CQDs capped with anions-CQD inks-are typically dispersed in highboiling-point solvents such as N, N-dimethylformamide (DMF) or N-methylformamide (MFA), which adds complexity to the production of sufficiently thick CQD films. [24] To produce CQD films directly from CQD inks, various approaches have been demonstrated, including centrifugal casting [7] and supersonic spray coating. [25] However, so far, these methods have been limited in scale to batch-processing; large-scale, single-step QD film formation has not yet been realized.One of the main challenges when forming films from CQD inks is to inhibit (or even control) the spatial redistribution of the dispersed solute during late-state evaporation. [26] This redistribution often results in poorly controlled film morphology Solution-processed colloidal quantum dots (CQDs) are attractive materials for the realization of low-cost and efficient optoelectronic devices. Although impressive CQD-solar-cell performance has been achieved, the fabrication of CQD films is still limited to laboratory-scale small areas because of the complicated deposition of CQD inks. Large-area, uniform deposition of lead sulfide (PbS) CQD inks is successfully realized for photovoltaic device applications by engineering the solute redistribution of CQD droplets. It is shown experimentally and theoretically that the solute-redistribution dynamics of CQD droplets are highly dependent on the movement of the contact line and on the evaporation kinetics of the solvent. By lowering the f...

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confidence: 92%

Tuning Solute‐Redistribution Dynamics for Scalable Fabrication of Colloidal Quantum‐Dot Optoelectronics

et al. 2019

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“…Recently, Weon and Je 23 showed that competition between the radially outward flow and Marangoni flow induces a fingering like pattern in a decalin droplet containing micro-and nanoparticles particles. Yang et al 24 used water droplets containing sulfate-modified polystyrene particles with different concentrations (0.1 to 0.5% v/v) and obtained various patterns (concentric multi-rings, radial spokes, spider web, foam and island like depositions) as a result of the opposition between the receding contact line and growth rate of the particle deposition during the evaporation.…”

Section: Studies On Non-heated Hydrophilic Substratesmentioning

confidence: 99%

Effects of Substrate Heating and Wettability on Evaporation Dynamics and Deposition Patterns for a Sessile Water Droplet Containing Colloidal Particles

et al. 2016

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Effects of substrate temperature, substrate wettability and particles concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid-gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and profile of final particle deposit is measured by an optical profilometer. On a non-heated hydrophilic substrate, a ring-like deposit forms after the evaporation, as reported extensively in the literature; while on a heated hydrophilic substrate, a thinner ring with an inner deposit is reported in the present work. The latter is attributed to Marangoni convection and recorded motion of the particles as well as measured temperature gradient across the liquid-gas interface confirms this hypothesis.The thinning of the ring scales with the substrate temperature and is reasoned to stronger Marangoni convection at larger substrate temperature. In case of a non-heated hydrophobic substrate, an inner deposit forms due to very early depinning of the contact line. On the other hand, in case of a heated hydrophobic substrate, the substrate heating as well as larger particle concentration helps in the pinning of the contact line, which results in a thin ring with an inner deposit. We propose a regime map for predicting three types of deposits namely, ring, thin ring with inner deposit and inner deposit -for varying substrate temperature, substrate wettability and particles concentration. A first-order model corroborates the liquid-gas interface temperature measurements and variation in the measured ring profile with the substrate temperature.3

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“…The ubiquitous characteristic of a ring formed by a drying colloidal droplet with a pinned contact line (CL) on a substrate, otherwise known as the "coffee-ring" effect, and the suppression thereof have been a central theme although it is markedly advantageous for some applications including coffee-ring lithography and transparent electronics 3,[7][8] . Since the seminal work done by Deegan et al 9 , a slew of studies have proven to successfully "tune" the coffee-ring effect via controlling the solvent composition, substrate temperature, particle size and concentration, and others [10][11][12][13][14][15][16][17][18][19][20][21][22] . Previously, Deegan's work has focused primarily on the evaporation-driven particle transport where the particles in millimetricsized volatile drops act as flow tracers and are characterized less by Brownian motion.…”

Section: Introductionmentioning

confidence: 99%

Colloidal Drop Deposition on Porous Substrates: Competition among Particle Motion, Evaporation, and Infiltration

Pack

Kim

et al. 2015

Langmuir

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Recent interest in printable electronics and in particular paper- and textile-based electronics has fueled research in inkjet printing of colloidal drops on porous substrates. On nonporous substrates, the interplay of particle motion and solvent evaporation determines the final deposition morphology of the evaporating colloidal drop. For porous substrates, solvent infiltration into the pores adds a layer of complexity to the deposition patterns that have not been fully elucidated in the literature. In this study, the deposition of picoliter-sized aqueous colloidal droplets containing nanometer- and micrometer-sized particles onto nanoporous anodic aluminum oxide substrates is examined for different drop and particle sizes and relative humidities as well as pore diameters, porosities, and wettabilities of the porous substrates. For the cases considered, solvent infiltration is found to be much faster than both evaporation and particle motion near the contact line, and thus when the substrate fully imbibes the solvent, the well-known "coffee-ring" deposition is suppressed. However, when the solvent is only partially imbibed, a residual droplet volume exists upon completion of the infiltration. For such cases, two time scales are of importance: the time for particle motion to the contact line as a result of both diffusion and advection, t(P), and the evaporation time of the residual drop volume, t(EI). Their ratio, t(P)/t(EI), determines whether the coffee-ring deposition will be formed (t(P)/t(EI) < 1) or suppressed (t(P)/t(EI) > 1).

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From multi-ring to spider web and radial spoke: competition between the receding contact line and particle deposition in a drying colloidal drop

Cited by 32 publications

References 37 publications

Tuning Solute‐Redistribution Dynamics for Scalable Fabrication of Colloidal Quantum‐Dot Optoelectronics

Tuning Solute‐Redistribution Dynamics for Scalable Fabrication of Colloidal Quantum‐Dot Optoelectronics

Effects of Substrate Heating and Wettability on Evaporation Dynamics and Deposition Patterns for a Sessile Water Droplet Containing Colloidal Particles

Colloidal Drop Deposition on Porous Substrates: Competition among Particle Motion, Evaporation, and Infiltration

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