Electrowetting force and velocity dependence on fluid surface energy

Ni, Qi; Capecci, Daniel E.; Crane, Nathan B.

doi:10.1007/s10404-015-1563-7

Cited by 21 publications

(18 citation statements)

References 32 publications

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“…One observation is that the actuation force profiles are similar to the velocity profiles in Figure 8 a. This means that if the droplet shape is constant or the deformation is much less, droplet velocity is mainly governed by the actuation force, which has been previously found in the literature [ 16 ].…”

Section: Discussionsupporting

confidence: 77%

“…For example, the average actuation force for a droplet with a rectangular contact area will be greater than that of a droplet with a circular contact area. In the case of a dynamic droplet, the shape itself is affected by the deformation that the droplet undergoes, and eventually it affects droplet velocity [ 16 , 18 ]. We will later show, in this study, that droplet deformation can be controlled by designing and operating electrodes in a certain way.…”

Section: Methodsmentioning

confidence: 99%

“…For achieving maximum droplet speed, it is necessary to identify the parameters to favorably tune the basic forces of the system to indirectly control the speed. Some parameters, such as liquid surface energy [ 16 , 17 ], liquid viscosity [ 17 ], contact angle hysteresis [ 17 ], contact line friction [ 16 , 17 ], dimensions [ 18 , 19 , 20 ] and shape of electrodes or droplet [ 20 , 21 , 22 ], gap between electrodes [ 18 , 20 ] and the channel height [ 19 ] have been investigated numerically [ 18 , 19 , 20 , 21 , 22 , 23 ] and experimentally [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

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Droplet Velocity in an Electrowetting on Dielectric Digital Microfluidic Device

et al. 2016

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In many electrowetting on dielectric (EWOD) based microfluidics devices, droplet actuation speed is a crucial performance-controlling parameter. Our present study aims to characterize and study droplet speed in a typical EWOD device. First, a practical droplet speed measurement method has been methodically demonstrated and some related velocity terms have been introduced. Next, influence of electrode shape on droplet speed has been studied and a new design to enhance droplet speed has been proposed and experimentally demonstrated. Instead of using square shaped electrodes, rectangular electrodes with smaller widths are used to actuate droplets. Additionally, different schemes of activating electrodes are studied and compared for the same applied voltage. The experiments show that a particular scheme of activating the array of rectangular electrodes enhances the droplet speed up to 100% in comparison to the droplet speed in a conventional device with square shaped electrodes.

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Section: Discussionsupporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Droplet Velocity in an Electrowetting on Dielectric Digital Microfluidic Device

et al. 2016

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“…It was found experimentally that the viscosity of the droplet had small impact on the actuation velocity (39). However, the viscous drag induced by the motion of the droplet can alter the droplet shape and reduce the speed of the droplet greatly (36,40). In applications where the shape of the interface is important (liquid lenses), it may be necessary to match the density of the ambient and electrolyte fluids as well.…”

Section: Electrolyte and Ambientmentioning

confidence: 96%

Electrowetting Effect: Theory, Modeling, and Applications

Crane

2015

Wiley Encyclopedia of Electrical and Electronics Engineering

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Electrowetting is a phenomenon in which an electric field at a fluid interface changes the equilibrium interface position. This is generally observed as a quadratic relationship between the applied voltage and the change in the cosine of the apparent contact angle. While the phenomena were first observed more than 100 years ago, until recently, applications were limited by poor reliability. The application of modern materials and manufacturing methods has enabled the fabrication of a wide range of devices that show excellent repeatability. Applications range from focusing lenses to miniature biomedical diagnostics and optical displays. The article reviews the basic electrowetting phenomena, the characteristics of key configurations, and key materials issues in fabricating reliable electrowetting devices. Some practical applications and modeling approaches of the electrowetting phenomena are also reviewed.

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“…Electrowetting forces have previously been controlled and measured although droplets on the millimeter scale are limited to forces in the micronewton range. 11 While droplet manipulation plays an important role in certain microfluidic and optoelectronic systems, actuation through direct electrocapillary action could still have an impact in a much broader range of applications where reversible mechanical force is required.…”

mentioning

confidence: 99%

Liquid metal actuator driven by electrochemical manipulation of surface tension

Russell

Wissman

Majidi

2017

Applied Physics Letters

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We examine the electrocapillary properties of a fluidic actuator composed of a liquid metal droplet that is submerged in electrolytic solution and attached to an elastic beam. The beam deflection is controlled by electrochemically driven changes in the surface energy of the droplet. The metal is a eutectic gallium-indium alloy that is liquid at room temperature and forms an nm-thin Ga 2 O 3 skin when oxidized. The effective surface tension of the droplet changes dramatically with oxidation and reduction, which are reversibly controlled by applying low voltage to the electrolytic bath. Wetting the droplet to two copper pads allows for a controllable tensile force to be developed between the opposing surfaces. We demonstrate the ability to reliably control force by changing the applied oxidizing voltage. Actuator forces and droplet geometries are also examined by performing a computational fluid mechanics simulation using Surface Evolver. The theoretical predictions are in qualitative agreement with the experimental measurements and provide additional confirmation that actuation is driven by surface tension.

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Electrowetting force and velocity dependence on fluid surface energy

Cited by 21 publications

References 32 publications

Droplet Velocity in an Electrowetting on Dielectric Digital Microfluidic Device

Droplet Velocity in an Electrowetting on Dielectric Digital Microfluidic Device

Electrowetting Effect: Theory, Modeling, and Applications

Liquid metal actuator driven by electrochemical manipulation of surface tension

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