On the Consistent Choice of Effective Permittivity andEffective Conductivity for Modeling Graphene

Many electrical and electromagnetic (EM) methods operate at MHz frequencies, at which the interfacial polarization occurring at the solid-liquid interface in geologic materials may dominate the electrical signals. To correctly interpret electrical/EM measurements, it is therefore critical to understand how the interfacial polarization influences the effective electrical conductivity and permittivity spectra of geologic materials. We have used pore-scale simulation to study the role of material texture and packing in interfacial polarization in water-saturated granular soils. Synthetic samples with varying material textures and packing densities are prepared with the discrete element method. The effective electrical conductivity and permittivity spectra of these samples are determined by numerically solving the Laplace equation in a representative elementary volume of the samples. The numerical results indicate that the effective permittivity of granular soils increases as the frequency decreases due to the polarizability enhancement from the interfacial polarization. The induced permittivity increment is mainly influenced by the packing state of the samples, increasing with the packing density. Material textures such as the grain shape and size distribution may also affect the permittivity increment, but their effects are less significant. The frequency characterizing the interfacial polarization (i.e., the characteristic frequency) is mainly related to the electrical contrast of the solid and water phases. The model based on the traditional differential effective medium (DEM) theory significantly underestimates the permittivity increment by a factor of more than two and overestimates the characteristic frequency by approximately 1 MHz. These inaccurate predictions are due to the fact that the electrical interactions between neighboring grains are not considered in the DEM theory. A simple empirical equation is suggested to scale up the theoretical depolarization factor of grains entering the DEM theory to account for the interaction of neighboring grains in granular soils.

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Effective permittivity of liquid crystal nanodispersions and composites with different pore structure

Phase Transitions ◽

10.1080/01411594.2018.1550639 ◽

2018 ◽

Vol 92 (1) ◽

pp. 79-86 ◽

Cited By ~ 2

Author(s):

Stanisław A. Różański

Keyword(s):

Liquid Crystal ◽

Pore Structure ◽

Effective Permittivity

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LTCC Packaged Ring Oscillator Based Sensor for Evaluation of Cell Proliferation

Sensors ◽

10.3390/s18103346 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3346 ◽

Cited By ~ 5

Author(s):

Joni Kilpijärvi ◽

Niina Halonen ◽

Maciej Sobocinski ◽

Antti Hassinen ◽

Bathiya Senevirathna ◽

...

Keyword(s):

Frequency Shift ◽

Flip Chip ◽

Effective Permittivity ◽

Complementary Metal Oxide Semiconductor ◽

Cellular Adhesion ◽

Sensor Response ◽

Lung Epithelial Cells ◽

Ring Oscillator ◽

Oxide Semiconductor ◽

Chip Surface

A complementary metal-oxide-semiconductor (CMOS) chip biosensor was developed for cell viability monitoring based on an array of capacitance sensors utilizing a ring oscillator. The chip was packaged in a low temperature co-fired ceramic (LTCC) module with a flip chip bonding technique. A microcontroller operates the chip, while the whole measurement system was controlled by PC. The developed biosensor was applied for measurement of the proliferation stage of adherent cells where the sensor response depends on the ratio between healthy, viable and multiplying cells, which adhere onto the chip surface, and necrotic or apoptotic cells, which detach from the chip surface. This change in cellular adhesion caused a change in the effective permittivity in the vicinity of the sensor element, which was sensed as a change in oscillation frequency of the ring oscillator. The sensor was tested with human lung epithelial cells (BEAS-2B) during cell addition, proliferation and migration, and finally detachment induced by trypsin protease treatment. The difference in sensor response with and without cells was measured as a frequency shift in the scale of 1.1 MHz from the base frequency of 57.2 MHz. Moreover, the number of cells in the sensor vicinity was directly proportional to the frequency shift.

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