Geometrically-controlled evaporation-driven deposition of conductive carbon nanotube patterns on inclined surfaces

Issakhani, Shervin; Jadidi, Omid; Farhadi, Jafar; Bazargan, Vahid

doi:10.1039/d2sm01431a

Cited by 7 publications

(9 citation statements)

References 66 publications

(111 reference statements)

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“…It should be noted that due to their larger size, alginate particles experience a drag force that is slightly greater than that of salt, [ 38 ] which leads to earlier deposition of alginate at the contact line. Also, in this RC range, sedimentation velocity that increases by the square of the particle size, [ 21 ] is not negligible anymore and causes the subsequent deposition at the inner region of the ring, as the contact line moves inward. Eventually, similar to the droplets with low RCs, the concentration of free ions increases, and above the saturation limit the crystal structure forms at the center of deposition.…”

Section: Resultsmentioning

confidence: 99%

“…Following Deegan et al's [17] landmark paper on contact line deposition, many experimental studies looked at the dynamics of evaporation and characterization of odd deposition patterns of colloidal sessile droplets. [18][19][20][21] The evaporative flux in sessile droplets with wetting contact angles is non-uniform, having the maximum value at the periphery and the minimum value at the center of the drop. [22] This non-uniformity, along with the contact line pinning, induces an outward flow field inside the droplet, also known as capillary flow, which can deposit suspended particles at the contact line.…”

Section: Introductionmentioning

confidence: 99%

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Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Biglari,

Saberi,

Issakhani

et al. 2023

Macro Materials & Eng

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Controllable patterning of bio‐compatible polymers in the presence of a cross‐linker in evaporating bi‐dispersed colloidal drops is of critical importance in functional coatings, bioprinting, and food packaging. This study investigates the effect of calcium chloride and sodium alginate concentration on the evaporative deposition and elemental distribution of dried‐out patterns. Different concentrations of alginate and salt in aqueous solutions are deposited on clean glass substrates to gain a deeper understanding of the final structures. Overall, the results indicate that changing the concentrations of sodium alginate and calcium chloride can significantly alter the elemental distribution and deposition uniformity of the final patterns. The modifications in relative concentration alter the physicochemical characteristics of the solution, resulting in significant changes in the pinning time and contact angle of the droplets that correspond to the alteration of the colloidal size and concentration, ultimately resulting in significant differences in deposition patterns. The dried‐out patterns are categorized based on their structures and mechanisms (crystallization, sedimentation, and adsorption) controlling the evaporative deposition, and then justified based on the competitive effects of cross‐linking, crystallization, and evaporation‐driven flows. Using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy, the elemental distribution of dried‐out patterns is also mapped to substantiate the discussion made.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Biglari,

Saberi,

Issakhani

et al. 2023

Macro Materials & Eng

Self Cite

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“…This is typically done in the context of lubrication theory (thin droplets), yielding an evolution equation without any other assumptions on the droplet shape. Hence the one-sided model is more amenable to describing droplets with asymmetric shapes (Charitatos, Pham & Kumar 2021;Issakhani et al 2023). At its edge, the droplet merges onto a precursor film of constant thickness that does not evaporate away due to the inclusion of disjoining pressure.…”

Section: One-sided Evaporationmentioning

confidence: 99%

Comparison of one-sided and diffusion-limited evaporation models for thin liquid droplets

Larsson,

Kumar

2023

J. Fluid Mech.

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Evaporating sessile droplets are critical to many industrial applications and are also ubiquitous in nature. Two predominant evaporation models have emerged in the literature, one-sided and diffusion-limited, with differing assumptions on the evaporation process. Both models are used widely, and their predictions can differ greatly from each other, but the physical mechanisms responsible for these differences are not yet well understood. Here, we develop a lubrication-theory-based model of a thin evaporating sessile droplet, and compare predictions from both evaporation models to elucidate the origins of the differences in their predictions. For the one-sided model, we derive expressions for the droplet lifetime, show that in certain parameter regimes the total evaporation rate is proportional to the droplet surface area, and demonstrate that the contact line is always warmer than the bulk of the droplet. Furthermore, we show that differences in the structures of the evaporation models near the contact line lead to qualitatively different behaviour of the apparent contact angles and interface temperature profiles. The fundamental understanding gained from this work is expected to be helpful in determining which evaporation model is most appropriate for describing experimental observations.

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“…For droplets on an incline, gravity may break the symmetry of an evaporating sessile droplet by, for example, altering the evaporation rate (Timm et al 2019;Tredenick et al 2021) or pinning time (Charitatos, Pham & Kumar 2021) compared with a sessile droplet on a flat substrate. These effects may also play a role in the coffee-ring phenomenon, leading to non-uniform ring-like stains (see, for example, Du & Deegan 2015;Issakhani et al 2023), more complex patterns after droplet depinning (Charitatos et al 2021), or in extreme cases where the droplet is pendant, the formation of a cone-like 'coffee eye' (Mondal et al 2018). Meanwhile, the recent upsurge in interest in binary droplets has been driven by, for example, the experiments of Edwards et al (2018), which showed that the dynamics of binary droplets can be sensitively dependent on both the component liquids (as well as droplet inclination), and hence, gravity.…”

Section: Introductionmentioning

confidence: 99%

“…These effects may also play a role in the coffee-ring phenomenon, leading to non-uniform ring-like stains (see, for example, Du & Deegan 2015; Issakhani et al. 2023), more complex patterns after droplet depinning (Charitatos et al. 2021), or in extreme cases where the droplet is pendant, the formation of a cone-like ‘coffee eye’ (Mondal et al.…”

Section: Introductionmentioning

confidence: 99%

Gravitational effects on coffee-ring formation during the evaporation of sessile droplets

Moore

Wray

2023

J. Fluid Mech.

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We consider the role of gravity in solute transport when a thin droplet evaporates. Under the physically relevant assumptions that the contact line is pinned and the solutal Péclet number, ${Pe}$ , is large, we identify two asymptotic regimes that depend on the size of the Bond number, ${Bo}$ . When ${Bo} = O(1)$ as ${Pe}\rightarrow \infty$ , the asymptotic structure of solute transport follows directly from the surface-tension-dominated regime, whereby advection drives solute towards the contact line, only to be countered by local diffusive effects, leading to the formation of the famous ‘coffee ring.’ In the distinguished limit in which ${Bo} = O({Pe}^{4/3})$ as ${Pe}\rightarrow \infty$ , this interplay between advection and diffusion takes place alongside that between surface tension and gravity. In each regime, we perform a systematic asymptotic analysis of the solute transport and compare our predictions to numerical simulations. We identify the effect of gravity on the nascent coffee ring, providing quantitative predictions of the size, location and shape of the solute mass profile. In particular, for a fixed Péclet number, as the effect of gravity increases, the coffee ring is diminished in height and situated further from the contact line. Furthermore, for certain values of ${Bo}$ , ${Pe}$ and the evaporation time, a secondary peak may exist inside the classical coffee ring. The onset of this secondary peak is linked to the change in type of the critical point in the solute mass profile at the droplet centre. Both the onset and the peak characteristics are shown to be independent of ${Pe}$ .

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Geometrically-controlled evaporation-driven deposition of conductive carbon nanotube patterns on inclined surfaces

Abstract: Controllable accumulation of carbon nanotubes in self-assembly techniques is of critical importance in smart patterning and printed electronics. This study investigates how inclining the substrate and inhibiting the droplet spreading...

Cited by 7 publications

References 66 publications

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Comparison of one-sided and diffusion-limited evaporation models for thin liquid droplets

Gravitational effects on coffee-ring formation during the evaporation of sessile droplets

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