Water, electricity, and between… On electrowetting and its applications

Shamai, Romi; Andelman, David; Berge, B.; Hayes, Rob

doi:10.1039/b714994h

Cited by 163 publications

(130 citation statements)

References 19 publications

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“…Because of their high dipole and quadrupole moments, water molecules feature strong interactions with electrostatic fields next to charged or polar solutes, and are attracted to field-exposed regions in electrowetting experiments 1 . Attractive interactions of water with electric field imply partial alignment of molecular dipoles with the direction of the field.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

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

Bratko

Daub

Luzar

2008

Phys. Chem. Chem. Phys.

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“…To date, research activities on the EWOD have produced impressive progresses and relevant information can be found in several review papers. [24][25][26][27] Zinc oxide (ZnO) is a low-cost semiconductor with direct wide band gap (3.36 eV at room temperature) and large exciton binding energy (60 mV). 28 Because the ZnO exhibits notable chemical stability and biological compatibility, it has attracted significant attention for applications in photocatalysis, electronics, optoelectronics, and sensors.…”

mentioning

confidence: 99%

Electrowetting of Superhydrophobic ZnO Inverse Opals

Chen

Lai

et al. 2011

J. Electrochem. Soc.

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ZnO inverse opals are fabricated by electrophoresis of polystyrene (PS) microspheres (720 nm in diameter) on a ITO glass to form a close-packed colloidal crystal, followed by potentiostatic deposition of ZnO in the interstitial voids among the PS microspheres and chemical removal of the PS colloidal template. By adjusting the electrodeposition time, we obtain semi-layered and multilayered ZnO inverse structures with significantly reduced defects and considerable surface uniformity. The semi-layered ZnO inverse opals display a bowl-like morphology with individual cavities isolated from each other. In contrast, the multi-layered ZnO inverse opals exhibit a three-dimensional skeleton with hexagonally-arranged cavities interconnected to each other. After surface coating of perfluorodecyltriethoxysilane, both samples reveal a superhydrophobic nature with contact angle larger than 150. In electrowetting measurements, the contact angles are decreasing with increasing applied voltages. The droplet on the semi-layered ZnO inverse opals demonstrates a notable transition from the Cassie-Baxter state to the Wenzel one. However, the droplet on the multi-layered ZnO inverse opals indicates three distinct regimes; Cassie-Baxter state, mixed Cassie-Baxter/Wenzel state, and Wenzel state. Repelling pressure of the entrapped air in the cavities is estimated to explain the observed contact angle variation upon the applied voltage for both samples. The surface property for a solid material can be deliberately controlled from hydrophilic to hydrophobic in order to affect the wetting behavior of a water droplet that is in contact with the solid surface. So far, external stimuli such as electric field, mechanical force, magnetic field, electrochemical reaction, and photon excitation have been employed to manipulate physical and chemical attributes of the surface.1-5 Among them, the electrical route, known as electrowetting (EW), is recognized for its fast response, reversibility, and compatibility with microdevices.6-8 To date, the implementation of EW for applications such as microfluidics and optoelectronic components have been explored. [9][10][11] In EW, the water droplet on the solid surface reveals a significant morphological alteration from a large contact angle (hydrophobic) to a reduced one (hydrophilic) upon the imposition of voltage across the solid surface and water droplet. This is because the electrical field engenders a capacitive charging on the interface that increases its surface energy considerably. As a result, the water droplet is able to wet the solid surface lowering the overall interfacial energy.For a desirable EW material, a large contact angle at zero voltage and a stronger capacitive effect are always preferred. To achieve these objectives, recent research attention has focused on the design and fabrication of one-dimensional materials such as nanowires and nanorods. [12][13][14][15] In general, the wetting behavior for the water droplet on a nanostructured surface can be categorized in Cassie-Baxter model o...

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“…The electrodes are coated with a thin insulating dielectric layer, which isolates them electrically from a conductive liquid, present on the other side of the coating. By applying a positive electrical field to the electrodes relative to the conducting liquid, the electrodes will attract the conductive liquid [12].…”

Section: Principle Of the Liquid Lensmentioning

confidence: 99%

3D-imaging: a scanning light pattern projector

Stokholm¹,

Hanson²,

Kjær³

et al. 2016

Appl. Opt.

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The technology of electrically adjustable optical interfaces has found applications in e.g. camera lenses, where an adjustable focal length provides automatic focusing for the camera. In this paper we will investigate a liquid lens, where both the focal length and the tilt of this lens can be adjusted electrically. Specifically, the tilting ability of this lens will be tested by combining the liquid lens with a projector in order to scan lines across a 3D object. Linearity, reproducibility, hysteresis and time response of its tilting functionality will be tested. Further, cross-talk between the two functionalities of the liquid lens is tested for the specific case, where the focal length is set to infinity. Finally, the liquid lens and the projector in combination with four stereo cameras will be demonstrated as a 3D imaging setup.

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Water, electricity, and between… On electrowetting and its applications

Cited by 163 publications

References 19 publications

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

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

Electrowetting of Superhydrophobic ZnO Inverse Opals

3D-imaging: a scanning light pattern projector

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