Self-Similar Interfacial Impedance of Electrodes in High Conductivity Media

Koklu, Anil; Mansoorifar, Amin; Beşkök, Ali

doi:10.1021/acs.analchem.7b03753

Cited by 14 publications

(19 citation statements)

References 56 publications

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“…The EP effect increases with decreased electrode size and increased buffer conductivity. Our studies along with others have shown that EP can be drastically reduced using electro deposition of fractal gold nanostructures, ,, platinum black, iridium oxide, PPy:PSS, and PEDOT:PPS, which will increase the device sensitivity in high conductivity media at the low frequency range, addressing the aforementioned limitations of the DS technique.…”

Section: Resultsmentioning

confidence: 70%

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

Mansoorifar

Koklu

et al. 2018

Anal. Chem.

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Dielectric spectroscopy (DS) is a noninvasive technique for real-time measurements of the impedance spectra of biological cells. DS enables characterization of cellular dielectric properties such as membrane capacitance and cytoplasmic conductivity. We have developed a lab-on-a-chip device that uses an electro-activated microwells array for capturing, DS measurements, and unloading of biological cells. Impedance measurements were conducted at 0.2 V in the 10 kHz to 40 MHz range with 6 s time resolution. An equivalent circuit model was developed to extract the cell membrane capacitance and cell cytoplasmic conductivity from the impedance spectra. A human prostate cancer cell line, PC-3, was used to evaluate the device performance. Suspension of PC-3 cells in low conductivity buffers (LCB) enhanced their dielectrophoretic trapping and impedance response. We report the time course of the variations in dielectric properties of PC-3 cells suspended in LCB and their response to sudden pH change from a pH of 7.3 to a pH of 5.8. Importantly, we demonstrated that our device enabled real-time measurements of dielectric properties of live cancer cells and allowed the assessment of the cellular response to variations in buffer conductivity and pH. These data support further development of this device toward single cell measurements.

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Section: Resultsmentioning

confidence: 70%

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

Mansoorifar

Koklu

et al. 2018

Anal. Chem.

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“…Therefore, the resistance of the microfluidic system is required to be able to accurately quantify the rate of heat generation. Microfluidic-based impedance spectroscopy is a useful technique for identifying the resistance of the system in a frequency spectrum. − A high-precision impedance analyzer (4194A, Agilent) is used to measure the impedance spectrum of the microfluidic device when filled with 1.4 S/m conductive PBS solution. The terminals of the side electrodes are connected to the low and high terminals of the impedance analyzer using a test fixture (HP 16047A) in a four terminal configuration and the measurements are carried out at 401 discrete frequency points from 100 Hz to 10 MHz at 20 mV.…”

Section: Materials and Methodsmentioning

confidence: 99%

Characterization of Temperature Rise in Alternating Current Electrothermal Flow Using Thermoreflectance Method

et al. 2019

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Alternating current electrothermal flow (ACET) induced by Joule heating is utilized to transport biologically relevant liquids in microchannels using simple electrode designs. However, Joule heating may cause significant temperature rises, which can degrade biological species, and hence, ACET may become impractical for biomicrofluidic sensors and other possible applications. In this study, the temperature rise at the electrode/electrolyte interface during ACET flow is measured using a high-resolution, noninvasive, thermoreflectance imaging method, which is generally utilized in microelectronics thermal imaging applications. The experimental findings reveal that Joule heating could result in an excessive temperature rise, exceeding 50 °C at higher voltage levels (20 Vpp). The measured data are compared with the results of the enhanced ACET theoretical model, which predicts the temperature rise accurately, even at high levels of applied voltages. Overall, our study provides a temperature measurement technique that is used for the first time for electrode/electrolyte systems. The reported results are critical in designing biomicrofluidic systems with significant energy dissipation in conductive fluids.

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“…Microfluidic device fabrication and the experimental procedure for measuring the impedance spectra of electrolyte between the parallel disk electrodes were explained in our previous article. 53 Briefly, 4 mm diameter disk shape gold electrodes were fabricated using a standard photolithography technique. The microfluidic channel was fabricated using double sided tape and sandwiched between the two glass slides where the gold electrodes are sputtered.…”

Section: ■ Setupmentioning

confidence: 99%

Self-Similar Response of Electrode Polarization for Binary Electrolytes in Parallel Plate Capacitor Systems

2019

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Classical electrochemistry problem of polarization of an electrode immersed in a symmetric binary electrolyte and subjected to a small external ac voltage is revisited. The Nernst−Planck equations are simplified to the Debye−Falkenhagen equation, which is solved together with the Poisson equation, leading to analytical formulas for the space charge density and impedance of the system for two parallel plate electrodes. We then define a limit of thin electrical double layer and illustrate the emergence of the characteristic time scale, τ c = λ D L/D, a function of the Debye length, λ D , the electrode separation distance, L, and the ionic diffusion coefficient D. Normalizing the impedance magnitude with the solution resistance and making the frequency dimensionless with the τ c , we show that all analytical, numerical, and experimental data for different solution conductivities and electrode separation distances collapse onto a single curve. To account for the Stern layer effects, we conducted numerical simulations based on the modified Poisson−Nernst−Planck model and showed that the results agree with our analytical solution for a range of concentrations, with small discrepancies observed only above 0.1 M. Based on the proposed model, experimental impedance spectroscopy results at ac potentials can be used to obtain detailed knowledge of the corresponding surface (and space) charge densities on the electrodes.

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Self-Similar Interfacial Impedance of Electrodes in High Conductivity Media

Cited by 14 publications

References 56 publications

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

Characterization of Temperature Rise in Alternating Current Electrothermal Flow Using Thermoreflectance Method

Self-Similar Response of Electrode Polarization for Binary Electrolytes in Parallel Plate Capacitor Systems

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