(a) Schematic graphs of the array configuration for three different electrodes. (a) The selected electrode (◼) is connected to impedance analyzer for the measurement while the rest of electrodes (◻) are connected to the virtual ground. (b) The configuration is analogous to a scanning coaxial probe.
Equivalent circuit model of monolithic CMOS. See Table I for the practical values of the components.
Block diagram of array architecture. See the text for a description of the significance of the symbols.
Impedance measurement system. (a) Complete system. (b) Close-up view of array.
(a) Equivalent electrical circuit describing a biological sample, represented by a parallel combination of capacitance and conductance , are connected in series with the electrode polarization impedance (a constant phase angle). The effect of total stray capacitance, PCB traces, and interfacing cable inductance are considered as and . Three calibration processes were employed to correct for the anomalies. (b) Equivalent (measured) electrical circuit of the sample.
Electrode array design.
Frequency dependence of relative permittivity and conductivity of NaCl solution at two different concentrations 10 mM (○) and 25 mM (◻). Solid lines (–) are best-fit theoretical simulations using the method described in Ref. 14.
Relative change in the permittivity and conductivity of 20 mM KCl solution as a function of sample thickness. The effective penetration depth is identified as the sample thickness at which the measured dielectric properties deviated from the values for the solution by 1%. Experimental value for was obtained 3.5 mm.
Relative change in permittivity and conductivity of 20 mM KCl solution as a function of distance between a metal rod and electrode (relative to the values measured in the absence of the metal rod) in two different cases: (a) the object is connected to the system ground and (b) the object is in floating condition.
Typical permittivity and conductivity spectra for yeast cells suspensions (○) and for the 20 mM KCl solution (◻) used to suspend the cells. Solid lines (–) are best-fit theoretical simulations using the equations described in Secs. II C and ???. Best-fit parameters for the KCl solution were: , , , ; For the cell suspension, the best fit parameters were: , , , , , , , and . The fitting residual, according to Eq. (6), was obtained: 7.2. Morphological parameters: , , , , and . The parameters which were fixed in the data fitting: , , , , and .
Three-shell model of a cell. is the complex permittivity and is defined as , where is dielectric constant and is the conductivity. In this equation, is the angular frequency of applied field. The indexes m, om, cp, w, and e correspond to the plasma membrane, organelle membrane, cytoplasm, wall, and external medium.
Frequency dependence of (a) relative permittivity and (b) conductivity of tissue phantom for three different locations of the cell suspension inclusion: inclusion on top of measuring electrode (△), on the top of a neighbor electrode (◻), and far from measuring electrode (○).
(a) A photograph of the phantom made by gel-containing salt (agar soaked in 20 mM KCl solution) and yeast cell. The samples (yeast cells suspended in KCl solution) were on the top of two selected electrodes. A 2D-map of the distribution of the (b) relative permittivity at 10.5 MHz and (c) conductivity at 120 KHz.
Electrical specification of three different analog switches.
A comparison of the membrane capacitance and cytoplasm conductivity obtained from this study to published reports.
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