Behavior of evaporating electrically charged droplets

The controlled formation and handling of minute liquid volumes on surfaces is essential to the success of microfluidics in biology, chemistry, and materials applications. Even though current methods have demonstrated their potential in a variety of experimental assays, there remain significant difficulties concerning breadth of applicability, standardization, throughput, and economics. Here we introduce a unique microfluidic paradigm in which microscopic volatile droplets are formed, sustained, and manipulated in size and content at any desired spot on unpatterned substrates. Their sustainability is warranted by continuous replacement of the rapidly vaporizing sessile fluid through controlled equivalent volume deposition of smaller discrete liquid entities by an electrohydrodynamic nanodripping process. Using nanoparticle inks we show that the concentration of solutes in so-stabilized droplets can be linearly increased at isochoric conditions and user-defined rates. An intriguing insensitivity of the droplet shape toward surface heterogeneities ensures robustness and experimental reproducibility, even when handling attoliter quantities. The unique capabilities and technical simplicity of the presented method introduce a high degree of flexibility and make it pertinent to a diverse range of applications.digital microfluidics | sessile droplets | noncontact printing

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“…S1). The deposited droplet therefore sustains charge neutrality, which in addition prevents its possible disintegration by Rayleigh fission (21).…”

Section: Resultsmentioning

confidence: 99%

Open-atmosphere sustenance of highly volatile attoliter-size droplets on surfaces

Galliker

Schneider

Rüthemann

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…The finite element solver of the FLUENT software is used for solving the transport equation of the continuous phase and discrete phase model in lagrangian coordinate. Since the energy of the droplet particles is much greater than the kinetic energy of random temperature, so the droplet particles' Brownian motion are ignored (Doyle et al, 1964). In the electrostatic spraying process, the specific calculation parameters are set as follows:…”

Section: Modelmentioning

confidence: 99%

The spraying field characteristics and distribution of deposition of droplets of electrostatic oiler

Wang¹,

Wang²,

Fan³

et al. 2016

J. Eng. Technol. Res.

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Electrostatic oiler are made as the research object, the multiple field spray characteristics of air flow field, electric field and discrete fog field in the process of spraying were analyzed. The influence of electrostatic spray deposition characteristics has been studied by changing the electrostatic voltage and electrode gap. The experiment about electrostatic oil spray has been verified. The results show that droplets of axial velocity are larger in the outlet of spray field near the larger intensity area. Near the metal plate, the air flow accelerates the droplets and makes the fog area diffused. Due to the droplets deposition and diffusion on the metal plate, the air is around in motion. With the electrostatic voltage increases, the droplet size decreases to a certain value then basically unchanged and afterwards the droplet size increases as the electrodes distance increases. The droplet deposition area increases first and then decreases with the increase in voltage, and then decreases with the increasing in electrodes distance; the density fluctuation of the droplet deposition is uniform and the deposition amount is moderate. When the voltage reaches 50 to 60 kV and the electrode spacing reaches 195 to 225 mm, the electrostatic spray atomization effect is better.

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“…[3][4][5][6] If Carlon's interpretation of his results is correct, it is to be expected that very large ion concentrations would cause greatly increased atmospheric electrical conductivity near the surface of the ocean or other bodies of water, within or near clouds or fog, or in the close vicinity of an evaporating water drop. Since that has not been observed (Gunn,7 Rust, 8 and Doyle 9 ), it would appear that it is at least as important to scrutinize Carlon's apparatus and the interpretation of his results as it is to follow his suggestion that the views presently held on atmospheric conductivity should be reexamined.…”

mentioning

confidence: 99%

Comments on ‘‘New measurements of the ion content of evaporation-humidified air’’

Vonnegut

Mohnen

1987

The Journal of Chemical Physics

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Behavior of evaporating electrically charged droplets

Cited by 167 publications

References 2 publications

Open-atmosphere sustenance of highly volatile attoliter-size droplets on surfaces

Open-atmosphere sustenance of highly volatile attoliter-size droplets on surfaces

The spraying field characteristics and distribution of deposition of droplets of electrostatic oiler

Comments on ‘‘New measurements of the ion content of evaporation-humidified air’’

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