Electrowetting at the Nanoscale

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

doi:10.1021/jp067395e

Cited by 145 publications

(219 citation statements)

References 48 publications

(94 reference statements)

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“…In a preceding study 54 , we presented a comparison between field effects on average numbers of hydrogen bonds determined by both the geometric 35 and energetic 55 criteria. Identical effects were found using either method, hence only the geometric definition is applied here.…”

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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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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“…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. 8,9 In particular, we highlighted the coupling between interfacial hydrogen bonds and molecular alignment in electric field. This coupling modulates the dependence on field direction and polarity in contrast with conventional picture in a macroscopic system discussed above; system size plays a crucial role.…”

Section: Introductionmentioning

confidence: 98%

“…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%

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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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“…16 Thus, the governing equation is the same as that at the macroscale if we define an electrowetting number at the microscale η m = C m V 2 /2γ LV , where C m is the effective capacitance per unit area. When a droplet electrowets on a rough surface, the situation becomes complicated.…”

Section: Introductionmentioning

confidence: 99%

Statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale

Zhao

Yuan

2015

Nanoscale

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The statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale are studied using molecular dynamics simulations. Under a gradually increased electric field, a droplet is pushed by the electromechanical force to spread, and goes through the Cassie state, the Cassie-to-Wenzel wetting transition and the Wenzel state, which can be characterized by the electrowetting number at the microscale η m . The expansion of the liquid is direction-dependent and influenced by the surface topology. A positive voltage is induced in the bulk droplet, while a negative one is induced in the liquid confined among the pillars, which makes the liquid hard to spread and further polarize. Based on the molecular kinetic theory and the wetting states, theoretical models have been proposed to comprehend the physical mechanisms in the statics and dynamics of electrowetting, and are validated by our simulations. Our findings may help to understand the electrowetting on microtextured surfaces and assist the future design of engineered surfaces in practical applications.

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Electrowetting at the Nanoscale

Cited by 145 publications

References 48 publications

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

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

Water-mediated ordering of nanoparticles in an electric field

Statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale

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