Patterns during Evaporative Crystallization of a Saline Droplet

Kumar, Virkeshwar; Dash, Susmita

doi:10.1021/acs.langmuir.2c01535

Cited by 2 publications

(2 citation statements)

References 50 publications

(88 reference statements)

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“…18 The evaporative deposit morphologies range from coffee-ring deposits on hydrophilic substrates 19 to condensed deposits on hydrophobic and liquid-impregnated surfaces. 20,21 On hydrophilic surfaces, the in-plane orientation of crystal growth along the substrate and pinning of salt crystals at the droplet triple contact line make removal of crystalline deposits difficult. 20 Localized salt deposits on hydrophobic surfaces are relatively easier to remove from the substrate due to lower adhesion between the deposits and the substrate compared to that on hydrophilic substrates.…”

Section: ■ Introductionmentioning

confidence: 99%

“…During evaporation of a saline droplet, crystallization occurs at a critical supersaturation depending on the interfacial surface energies. , The evaporative deposition pattern of saline droplets depends on the initial contact angle and contact angle hysteresis that determine the droplet evaporation mode . The evaporative deposit morphologies range from coffee-ring deposits on hydrophilic substrates to condensed deposits on hydrophobic and liquid-impregnated surfaces. , On hydrophilic surfaces, the in-plane orientation of crystal growth along the substrate and pinning of salt crystals at the droplet triple contact line make removal of crystalline deposits difficult . Localized salt deposits on hydrophobic surfaces are relatively easier to remove from the substrate due to lower adhesion between the deposits and the substrate compared to that on hydrophilic substrates.…”

Section: Introductionmentioning

confidence: 99%

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Generality of Evaporative Crystal Liftoff on Heated Hydrophobic Substrates

et al. 2023

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Scaling or mineral fouling occurs due to the presence of dissolved minerals in water. Scaling is problematic in numerous industrial and household plumbing applications where water is used. The current methods of scale removal often utilize harsh chemicals that are not environmentally friendly. The evaporation of a saline droplet provides a platform to study the role of the substrate in the dynamics of crystallization during scaling. In the present work, we show out-of-plane growth of crystal deposits during the evaporation of saline droplets of aqueous potassium chloride on a heated smooth and microtextured hydrophobic substrate. These out-of-plane deposits, termed as “crystal legs”, are in minimal contact with the substrate and can be easily removed from the substrate. The out-of-plane evaporative crystallization of saline droplets of different initial volumes and concentrations is observed irrespective of the chemistry of the hydrophobic coating and the crystal habits investigated. We attribute this general behavior of crystal legs to the growth and stacking of smaller crystals (size ∼10 μm) between the primary crystals toward the end of evaporation. We show that the rate at which the crystal legs grow increases with an increase in the substrate temperature. A mass conservation model is applied to predict the leg growth rate, which agrees well with the experiments.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Generality of Evaporative Crystal Liftoff on Heated Hydrophobic Substrates

et al. 2023

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Crystal Patterning from Aqueous Solutions via Solutal Instabilities

McBride,

Atis,

Pahlavan

et al. 2024

ACS Appl. Mater. Interfaces

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Fluid instabilities can be harnessed for facile selfassembly of patterned structures on the nano-and microscale. Evaporative self-assembly from drops is one simple technique that enables a range of patterning behaviors due to the multitude of fluid instabilities that arise due to the simultaneous existence of temperature and solutal gradients. However, the method suffers from limited controllability over patterns that can arise and their morphology. Here, we demonstrate that a range of distinct crystalline patterns including hexagonal arrays, branches, and sawtooth structures emerge from evaporation of water drops containing calcium sulfate on hydrophilic and superhydrophilic substrates. Different pattern regimes emerge as a function of contact line dynamics and evaporation rates, which dictate which fluid instabilities are most likely to emerge. The underlying physical mechanisms behind instability for controlled self-assembly involve Marangoni flows and forced wetting/dewetting. We also demonstrate that these patterns composed of water-soluble inorganic crystals can serve as sustainable and easily removable masks for applications in microscale fabrication.

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Patterns during Evaporative Crystallization of a Saline Droplet

Cited by 2 publications

References 50 publications

Generality of Evaporative Crystal Liftoff on Heated Hydrophobic Substrates

Generality of Evaporative Crystal Liftoff on Heated Hydrophobic Substrates

Crystal Patterning from Aqueous Solutions via Solutal Instabilities

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