A parallel-plate capacitor used to determine the complex permittivity of supercooled aqueous solutions in the 1 MHz range

Wolter, Fritz; Thom, F.

doi:10.1088/0957-0233/7/8/018

Cited by 5 publications

(7 citation statements)

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“…The cell deformations for 100 kHz and 1 MHz are of the same order of magnitude, so that the electric forces stretching the cell are constant within this frequency interval. For oi (25°C, 100 kHz) = 4.5 X 10-3 S/cm, O,e = 1.54 X10-4 S/cm (Wolter and Thom, 1996;F. Thom, in preparation) and U°ore = 1 V we obtain from Eq. 1 E°ore = 1640 V/cm, which is very close to the measured value for Elysis.…”

Section: Electrical Breakdown and Field-induced Hemolysismentioning

confidence: 89%

“…These results and our input data are summarized in Table 1. The conductivities of external (LISS) and internal (cytoplasm) media have been taken from impedance measurements for v = 1 MHz (Wolter and Thom, 1996;Thom and Wolter, in preparation). E°oreI and Epore2 are the critical field strengths for U0Ooe = 1 and 0.8 V, respectively, and the geometric parameters were calculated for a mean size of an elongated cell within this critical interval by numerical integration of Eq.…”

Section: Electrical Breakdown and Field-induced Hemolysismentioning

confidence: 99%

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Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures

Krueger¹,

Thom²

1997

Biophysical Journal

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High-frequency electric fields can be used to induce deformation of red blood cells. In the temperature domain T = 0 degrees to -15 degrees C (supercooled suspension) and for 25 degrees C this paper examines for human erythrocytes (discocytes, young cell population suspended in a low ionic strength solution with conductivity sigma(25 degrees) = 154 microS/cm) in a sinusoidal electric field (nu = 1 MHz, E0 = 0-18 kV/cm) the following properties and effects as a function of field strength and temperature: 1) viscoelastic response, 2) (shear) deformation (steady-state value obtained from the viscoelastic response time), 3) stability (by experimentally observed breakdown of cell polarization and hemolysis), 4) electrical membrane breakdown and field-induced hemolysis (theoretical calculations for ellipsoidal particles), and 5) mechanical hemolysis. The items 2-4 were also examined for the frequency nu = 100 kHz and for a nonionic solution of very low conductivity (sigma(25 degrees) = 10 microS/cm) to support our interpretations of the results for 1 MHz. Below 0 degrees C with decreasing temperature the viscoelastic response time tau(res)(T) for the cells to reach steady-state deformation values d(infinity,E) increases and the deformation d(infinity,E)(T) decreases strongly. Both effects are especially high for low field strengths. The longest response time of approximately 30 s was obtained for -15 degrees C and small deformations. For 1 MHz the cells can be highly elongated up to 2.3 times their initial diameter a0 for 25 degrees and 0 degrees C, 2.1a0 for -10 degrees C and still 1.95a0 for -15 degrees C. For T > or = 0 degrees C the deformation is limited by hemolysis of the cells, which sets in for E0(lysis)(25 degrees) approximately 8 kV/cm and E0(lysis)(0 degrees) approximately 14 kV/cm. These values are approximately three times higher than the corresponding calculated critical field strengths for electrically induced pore formation. Nevertheless, the observed depolarization and hemolysis of the cells is provoked by electrical membrane breakdown rather than by mechanical forces due to the high deformation. For the nonionic solution, where no electrical breakdown is expected in the whole range for E0, the cells can indeed be deformed to even higher values with a low hemolytic rate. Below 0 degrees C we observe no hemolysis at all, not even for the frequency 100 kHz, where the cells hemolyze at 25 degrees C for the much lower field strength E0(lysis) approximately 2.5 kV/cm. Obviously, pore formation and growth are weak for subzero temperatures.

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Section: Electrical Breakdown and Field-induced Hemolysismentioning

confidence: 89%

Section: Electrical Breakdown and Field-induced Hemolysismentioning

confidence: 99%

Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures

Krueger¹,

Thom²

1997

Biophysical Journal

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“…Fringing fields are widely known for plate capacitors which till this day are popular cells for measurement in the frequency range between 10 -6 and 10 7 Hz [312][313][314][315][316][317]. As already discovered by Kirchhoff [315], the fringing field contributions to the capacitance of a spherical plate capacitor filled with a sample of complex permittivity εtot(ν) = ε(ν) -iσ/(ε0ω) amount to…”

Section: Specimen Cells Electrode Polarizationmentioning

confidence: 99%

“…As suggested intuitively, the edge effects are especially strong at large d. In measurements at small sample conductivity σ, as small as possible d/rC ratios are thus to be preferred. Alternatively, contributions from fringing fields may be avoided by three-terminal guard-ring capacitor cells [313,315,[317][318][319][320]. As indicated by the schematic in Figure 58, the guard ring and the shielded center electrode are kept at identical potential but, in order to prevent contributions from the fringing field, only the current charging the center electrode is measured.…”

Section: Specimen Cells Electrode Polarizationmentioning

confidence: 99%

Electromagnetic moisture measurement

Hübner¹,

Kaatze²

2016

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XII which we believe to be useful when considering the design of special sensors and appropriate measurement techniques for moisture determination. A chapter dealing with the dielectric properties of water in its different states of interaction is also included. It is intended to provide information concerning the adequate modelling of data derived from the electromagnetic signals when affected by moist materials. Selected applications are discussed in order to introduce some proven examples of electromagnetic moisture sensors and related measurement methods. Finally, a collection of dielectric data for liquids is presented which may serve as reference in calibration procedures. Preferably data obtained from calibration-free methods is given. Additionally, most of it has been measured at different laboratories and the different series of data agree within the limits of experimental uncertainty. A detailed bibliography is provided in order to assist with further reading. We are indebted to Alexander Brandelik, Karlsruhe, who spent much time to critically read the manuscript before publication. We thank Alexander Schaub, Mannheim, for valuable help with editing the book, including proofreading and formatting.

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“…Parallel plate capacitors rely on trapping the electric field in the region between the plates, [15,16] which provides an inherent confinement of the measuring field between the two plates, with little interference due to external fields/objects. Only a small portion of the field is exposed to the external media causing fringing effects at the corners and edges of the plates.…”

Section: Introductionmentioning

confidence: 99%

Twin-T Oscillator Containing Polymer Coated Parallel Plate Capacitor for Sea Water Salinity Sensing

Bhatt¹,

Rahman²,

Arya³

et al. 2013

OJAB

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This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring. This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (Accuflo™) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coating in sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.

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A parallel-plate capacitor used to determine the complex permittivity of supercooled aqueous solutions in the 1 MHz range

Cited by 5 publications

References 0 publications

Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures

Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures

Electromagnetic moisture measurement

Twin-T Oscillator Containing Polymer Coated Parallel Plate Capacitor for Sea Water Salinity Sensing

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