Electrically driven oscillations of a mercury-droplet electrode

Smithwick, R.W.; Boulet, J. A. M.

doi:10.1016/0021-9797(92)90225-b

Cited by 10 publications

(3 citation statements)

References 13 publications

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“…For liquids in contact with solid the primary geometries which have been investigated include pendant or sessile drops, [16][17][18] the brimful cylinder, 19,20 and capillary bridges. [21][22][23][24][25][26] Damping measurements for capillary modes have been made on free drops, 7,8,10 bubbles, 13,14 and capillary bridges.…”

Section: Introductionmentioning

confidence: 99%

Enhanced damping of capillary bridge oscillations using velocity feedback

2005

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In reduced gravity, the stability of cylindrical liquid bridges and other systems having free surfaces is affected by ambient vibrations of the spacecraft. Such vibrations are expected to excite capillary modes. The lowest-order unstable mode of a liquid bridge is particularly susceptible to vibration as the length of the bridge approaches the stability limit. This mode is known as the ͑2,0͒ mode and is an axisymmetric varicose mode of one wavelength in the axial direction. In this work, an optical system is used to detect the ͑2,0͒-mode amplitude. The derivative of the error signal produced by this detector is used to produce the appropriate voltages on a pair of annular disk electrodes which are concentric with the bridge. A mode-coupled Maxwell stress profile is thus generated in proportion to the modal velocity. Depending on the sign of the gain, the damping of the capillary oscillation can be either increased or decreased. This effect has been demonstrated in Plateau-tank experiments. Increasing the damping of the capillary modes on free liquid surfaces in space could be beneficial for containerless processing and other technologies.

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Section: Introductionmentioning

confidence: 99%

Enhanced damping of capillary bridge oscillations using velocity feedback

2005

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“…Inserting the measured dependence shown before that oscillations of the mercury beating heart can be driven by externally imposed electrical oscillations 18,19 . Analogously, we have driven the system externally (Fig.…”

Section: Evaluation Of the Measurementsmentioning

confidence: 99%

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Maiworm¹,

Markus²

2005

ScienceAsia

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A drop of a solution of potassium dichromate and sulphuric acid was placed on the surface of mercury around an iron needle immersed in the mercury. We observed circular, as well as irregularly swirling oscillations of this drop. We could explain this phenomenon as follows. Electrochemical oscillations occur at the iron-solution interface; these cause oscillations of the potential at the drop's bottom, and thus of the drop' s shape by virtue of electrocapillarity. Our measurements allowed us to determine the surface tension and the capacity of the double-layer at the mercury-solution interface, as functions of voltage. We observed and explain a much faster electrical loading, as compared to the unloading, of the double-layer. Furthermore, we observed a negative differential electrical capacity.

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“…Thus, for a droplet of known surface ten-a͒ sion ␥, density , spherical radius R, and resonant frequency f 1 , the contact angle can be determined from the lowest-mode eigenvalue 1 ͑͒ calculated from the above equation. 6,9,10 Strictly speaking, driving the droplet oscillations with the horizontal AC electric field does not induce purely axisymmetric vibration modes as the driving force is perpendicular to the axis of symmetry of a sessile droplet. However, we show here that in the limit of small nonaxisymmetric deformations and large contact angles, droplet resonant frequencies determined sequentially using PZT ͑axisymmetric͒ and horizontal field ͑non-axisymmetric͒ driving are very close.…”

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confidence: 99%

Determination of microdroplet contact angles using electrically driven droplet oscillations

Karadağ¹,

Jonáš²,

Taşaltın³

et al. 2011

Applied Physics Letters

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Oscillatory deformations of micrometer-sized NaCl-water droplets by an AC electric field are used for contact angle measurements on superhydrophobic surfaces. Contact angles are determined from the dependence of the lowest-order resonant frequency of the electrically driven droplet oscillations on the droplet size. The resonant frequency and size of a droplet are found using whispering gallery mode spectroscopy. Measurements are compared with those performed with direct mechanical driving of the droplets using a piezoelectric transducer, and a good agreement is found. The demonstrated contact angle measurement method can be readily integrated into the planar architecture of microfluidic chips.

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Electrically driven oscillations of a mercury-droplet electrode

Cited by 10 publications

References 13 publications

Enhanced damping of capillary bridge oscillations using velocity feedback

Enhanced damping of capillary bridge oscillations using velocity feedback

Untitled

Determination of microdroplet contact angles using electrically driven droplet oscillations

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