Modulation of evaporation-affected crystal motion in a drying droplet by saline and surfactant concentrations

Shao, Xiaoxiao; Hou, Yu; Zhong, Xin

doi:10.1016/j.colsurfa.2021.126701

Cited by 16 publications

(7 citation statements)

References 58 publications

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“…In our experiments, this hysteresis is strengthened by the pinning of the triple line arising from the coffee-stain effect inevitable under evaporation of saline droplets [24][25][26][27][28][29][30]. The coffee-stain effect is evidenced by the formation of NaCl crystals close to the triple line, as depicted in Figure 2.…”

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confidence: 58%

Oscillatory Reversible Osmotic Growth of Sessile Saline Droplets on a Floating Polydimethylsiloxane Membrane

Roy

Shoval

Dombrovsky

et al. 2021

Fluids

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We report a cyclic growth/retraction phenomena observed for saline droplets placed on a cured poly (dimethylsiloxane) (PDMS) membrane with a thickness of 7.8 ± 0.1 µm floating on a pure water surface. Osmotic mass transport across the micro-scaled floating PDMS membrane provided the growth of the sessile saline droplets followed by evaporation of the droplets. NaCl crystals were observed in the vicinity of the triple line at the evaporation stage. The observed growth/retraction cycle was reversible. A model of the osmotic mass transfer across the cured PDMS membrane is suggested and verified. The first stage of the osmotic growth of saline droplets is well-approximated by the universal linear relationship, whose slope is independent of the initial radius of the droplet. The suggested physical model qualitatively explains the time evolution of the droplet size. The reported process demonstrates a potential for use in industrial desalination.

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confidence: 58%

Oscillatory Reversible Osmotic Growth of Sessile Saline Droplets on a Floating Polydimethylsiloxane Membrane

Roy

Shoval

Dombrovsky

et al. 2021

Fluids

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“…In the so-called “stick-slip” motion, the motion of the contact line consists of both CCR and CCA modes . Because of the coupled energy and mass transfer, and the complex physics involved, evaporation of sessile droplets on solid surfaces exhibits intriguing features, such as surface tension gradient-induced flowerlike patterning of an evaporation droplet spreading on a liquid surface, contraction of evaporating binary-liquid sessile, modulation of evaporation-affected crystal motion in drying saline droplets by varying the saline and surfactant concentrations, hollow rim formation on salt substrates due to droplet evaporation, and deposits with nonuniform width mediated by substrate heating with a temperature gradient, to name a few. Recently, researchers have also taken a keen interest in looking at sessile droplet evaporation dynamics on inclined substrates , and soft substrates …”

Section: Introductionmentioning

confidence: 99%

Size-Dependent Dried Colloidal Deposit and Particle Sorting via Saturated Alcohol Vapor-Mediated Sessile Droplet Spreading

2022

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We experimentally and theoretically investigate a distinct problem of spreading, evaporation, and the associated dried deposits of a colloidal particle-laden aqueous sessile droplet on a surface in a saturated alcohol vapor environment. In particular, the effect of particle size on monodispersed suspensions and efficient self-sorting of bidispersed particles have been investigated. The alcohol vapor diffuses toward the droplet's curved liquid−vapor interface from the far field. The incoming vapor mass flux profile assumes a nonuniform pattern across the interface. The alcohol vapor molecules are adsorbed at the liquid−vapor interface, which eventually leads to absorption into the droplet's liquid phase due to the miscibility. This phenomenon triggers a liquid−vapor interfacial tension gradient and causes a reduction in the global surface tension of the droplet. This results in a solutal Marangoni flow recirculation and spontaneous droplet spreading. The interplay between these phenomena gives rise to a complex internal fluid flow within the droplet, resulting in a significantly modified and strongly particle-size-dependent dried colloidal deposit. While the smaller particles form a multiple ring pattern, larger particles form a single ring, and additional "patchwise" deposits emerge. High-speed visualization of the internal liquid-flow revealed that initially, a ring forms at the first location of the contact line. Concurrently, the Marangoni flow recirculation drives a collection of particles at the liquid−vapor interface to form clusters. Thereafter, as the droplet spreads, the smaller particles in the cluster exhibit a "jetlike" outward flow, forming multiple ring patterns. In contrast, the larger particles tend to coalesce together in the cluster, forming the "patchwise" deposits. The widely different response of the different-sized particles to the internal fluid flow enables an efficient sorting of the smaller particles at the contact line from bidispersed suspensions. We corroborate the measurements with theoretical and numerical models wherever possible.

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“…Early images reveal the emergence of a thin quasi-crystalline layer due to rapid evaporation along the droplet edges (see Figure S1), illustrated as a light gray shell in Figure b. Evaporation-induced Marangoni flows could also transport nanocrystals from the bulk to the periphery, resulting in accumulation and deposition along the edges. , As electrostatic forces build up from charge accumulation, droplets fission into smaller satellite droplets, forming precipitates of the salt crystals, in this case, hexagonal and square NaOH crystals. Due to strong hygroscopic properties, NaOH precipitates attract and absorb water from the surrounding environment, predominantly from the mother droplet.…”

Section: Resultsmentioning

confidence: 99%

Time-Resolved Dynamic Crystallization at Liquid/Vapor Interface

Leong

Tong

et al. 2022

J. Phys. Chem. C

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We report the behavior of nanodroplets containing aqueous NaOH solutions of different concentrations, visualized using transmission electron microscopy (TEM). Under e-beam irradiation, highly charged aqueous NaOH droplets dewet with edge crystallization before erupting into satellite nanodroplets. For the first time, we observe dynamic nanocrystal precipitation from nanodroplet followed by redissolution in a periodic manner. Time-resolved images show that the crystalline precipitates occur predominantly in two distinct geometric shapeshexagonal and square. Through structural, elemental, and morphological analyses, we deduce that the crystalline precipitate is monohydrate NaOH·H2O, whose orthorhombic structure forms the underlying basis for the evolved crystalline shapes. Through numerical simulations, we show how the observed preferential orientation of the crystal precipitate depends on crystal morphology and relative droplet–crystal size, but not on electrical forces, which govern droplet deformations. Together, our results reveal strong dynamics at the interface, including ionic chemistry, nanoscale physics, and hydrodynamics.

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Modulation of evaporation-affected crystal motion in a drying droplet by saline and surfactant concentrations

Cited by 16 publications

References 58 publications

Oscillatory Reversible Osmotic Growth of Sessile Saline Droplets on a Floating Polydimethylsiloxane Membrane

Oscillatory Reversible Osmotic Growth of Sessile Saline Droplets on a Floating Polydimethylsiloxane Membrane

Size-Dependent Dried Colloidal Deposit and Particle Sorting via Saturated Alcohol Vapor-Mediated Sessile Droplet Spreading

Time-Resolved Dynamic Crystallization at Liquid/Vapor Interface

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