Effect of Field Direction on Electrowetting in a Nanopore

Bratko, D.; Daub, Christopher D.; Leung, Kevin; Luzar, Alenka

doi:10.1021/ja0659370

Cited by 174 publications

(267 citation statements)

References 56 publications

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“…The density increase depends on the angle +, being most pronounced when the field is parallel to the walls ($=0). In perpendicular field, electrostriction is weaker overall and strong asymmetry in the density profile is observed 9 . Similar asymmetry has been observed by other groups 6,7,25 .…”

Section: Resultsmentioning

confidence: 99%

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Water-mediated ordering of nanoparticles in an electric field

2009

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Interfacial polar molecules feature a strongly anisotropic response to applied electric field, favoring dipole orientations parallel to the interface. In water, in particular, this effect combines with generic orientational preferences induced by spatial asymmetry of water hydrogen bonding under confined geometry, which may give rise to a Janus interface. The two effects manifest themselves in considerable dependence of water polarization on both the field direction relative to the interface, and the polarity (sign) of the field. Using molecular simulations, we demonstrate strong field-induced orientational forces acting on apolar surfaces through water mediation. At a field strength comparable to electric fields around a DNA polyion, the torques we predict to act on an adjacent nanoparticle are sufficient to overcome thermal fluctuations. These torques can align a particle with surface as small as 1 nm 2 . The mechanism can support electrically controlled ordering of suspended nanoparticles as a means of tuning their properties, and can find application in electro-nanomechanical devices.

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Section: Resultsmentioning

confidence: 99%

“…Molecular level studies of these phenomena [6][7][8][9] , however, can bring in an entirely new perspective. In our recent work we demonstrated the importance of molecular scale events in understanding and making quantitative predictions of electrowetting phenomena in a nanoscale system.…”

Section: Introductionmentioning

confidence: 99%

Water-mediated ordering of nanoparticles in an electric field

2009

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“…S2). The contact angle dependency on the droplet size was reported previously (30,31). We checked the contact angle variation by using the droplet consisting of 2,180, 4,000, and 8,000 water molecules for facets of the above size as well as twice-larger size.…”

Section: Methodsmentioning

confidence: 98%

“…Note that the porosity of films (Fig. S1) as well as the atomic level morphology of the surface can affect the contact angle in the heterogeneous surface (30,31). However, the contact angle on the homogeneous surface allows rather straightforward comparison between experiment and simulation results (32), and many previous hydrophilic conversion experiments on TiO 2 were based on the homogeneous surfaces, which makes our assumptions probable.…”

Section: Significancementioning

confidence: 99%

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Lee

Kim

et al. 2014

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

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Titania, which exhibits superwetting under light illumination, has been widely used as an ideal material for environmental solution such as self-cleaning, water-air purification, and antifogging. There have been various studies to understand such superhydrophilic conversion. The origin of superwetting has not been clarified in a unified mechanism yet, which requires direct experimental investigation of the dynamic processes of water-layer growth. We report in situ measurements of the growth rate and height of the photo-adsorbed water layers by tip-based dynamic force microscopy. For nanocrystalline anatase and rutile TiO 2 we observe light-induced enhancement of the rate and height, which decrease after O 2 annealing. The results lead us to confirm that the long-range attraction between water molecules and TiO 2 , which is mediated by delocalized electrons in the shallow traps associated with O 2 vacancies, produces photo-adsorption of water on the surface. In addition, molecular dynamics simulations clearly show that such photo-adsorbed water is critical to the zero contact angle of a water droplet spreading on it. Therefore, we conclude that this "water wets water" mechanism acting on the photoadsorbed water layers is responsible for the light-induced superwetting of TiO 2 . Similar mechanism may be applied for better understanding of the hydrophilic conversion of doped TiO 2 or other photo-catalytic oxides.

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“…Carlo simulations 12,16 . An alternative setup, particularly suitable in Molecular Dynamics studies involves a simulation of both the confinement and bulk, field-free environment (reservoir) in equilibrium with each other 14,15 .…”

Section: Interactions Among Water Molecules Aligned By Applied Electrmentioning

confidence: 99%

Field-exposed water in a nanopore: liquid or vapour?

Bratko

Daub

Luzar

2008

Phys. Chem. Chem. Phys.

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Field-exposed water behaviour in hydrophobic confinement confirms classical electrostriction in nanoscale channels and nanoporous materials. 2 AbstractWe study the behavior of ambient temperature water under the combined effects of nanoscale confinement and applied electric field. Using molecular simulations we analyze the thermodynamic causes of field-induced expansion at some, and contraction at other conditions. Repulsion among parallel water dipoles and mild weakening of interactions between partially aligned water molecules prove sufficient to destabilize the aqueous liquid phase in isobaric systems in which all water molecules are permanently exposed to a uniform electric field. At the same time, simulations reveal comparatively weak field-induced perturbations of water structure upheld by flexible hydrogen bonding.In open systems with fixed chemical potential, these perturbations do not suffice to offset attraction of water into the field; additional water is typically driven from unperturbed bulk phase to the field-exposed region. In contrast to recent theoretical predictions in the literature, our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale channels and nanoporous materials.

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Effect of Field Direction on Electrowetting in a Nanopore

Cited by 174 publications

References 56 publications

Water-mediated ordering of nanoparticles in an electric field

Water-mediated ordering of nanoparticles in an electric field

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Field-exposed water in a nanopore: liquid or vapour?

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Effect of Field Direction on Electrowetting in a Nanopore

Cited by 174 publications

References 56 publications

Water-mediated ordering of nanoparticles in an electric field

Water-mediated ordering of nanoparticles in an electric field

Superwetting of TiO 2 by light-induced water-layer growth via delocalized surface electrons

Field-exposed water in a nanopore: liquid or vapour?

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Product

Resources

About

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons