Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

Matko, Vojko; Milanovič, M.

doi:10.3390/s21103565

Cited by 8 publications

(11 citation statements)

References 34 publications

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“…A recent improved method for dielectric measurement of liquids proposed by Matko et al could be explored for enhanced capacitance characterization of tissues in a culture medium or 3D cell cultures. This method, based on a capacitive-dependent quartz crystal and two quartz oscillators, provided high sensitivity and accuracy [ 26 ].…”

Section: Discussionmentioning

confidence: 99%

Electrical Impedance-Based Characterization of Hepatic Tissue with Early-Stage Fibrosis

et al. 2022

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Liver fibrosis is a key pathological precondition for hepatocellular carcinoma in which the severity is confidently correlated with liver cancer. Liver fibrosis, characterized by gradual cell loss and excessive extracellular matrix deposition, can be reverted if detected at the early stage. The gold standard for staging and diagnosis of liver fibrosis is undoubtedly biopsy. However, this technique needs careful sample preparation and expert analysis. In the present work, an ex vivo, minimally destructive, label-free characterization of liver biopsies is presented. Through a custom-made experimental setup, liver biopsies of bile-duct-ligated and sham-operated mice were measured at 8, 15, and 21 days after the procedure. Changes in impedance were observed with the progression of fibrosis, and through data fitting, tissue biopsies were approximated to an equivalent RC circuit model. The model was validated by means of 3D hepatic cell culture measurement, in which the capacitive part of impedance was proportionally associated with cell number and the resistive one was proportionally associated with the extracellular matrix. While the sham-operated samples presented a decrease in resistance with time, the bile-duct-ligated ones exhibited an increase in this parameter with the evolution of fibrosis. Moreover, since the largest difference in resistance between healthy and fibrotic tissue, of around 2 kΩ, was found at 8 days, this method presents great potential for the study of fibrotic tissue at early stages. Our data point out the great potential of exploiting the proposed needle setup in clinical applications.

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Section: Discussionmentioning

confidence: 99%

Electrical Impedance-Based Characterization of Hepatic Tissue with Early-Stage Fibrosis

et al. 2022

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“…Nevertheless, the current‐voltage measurement is not suitable for a characterization that is less than 10‐nm nanogap structures, because the applications of high voltage may cause current leakage and this could damage the device 174 . Impedance spectroscopy was applied to rigorously characterize the nanogap‐based electrical devices and predicted a model 175 . The parameters such as sensitivity to permittivity changes were also predicted by the model and compared with the measured values 176 .…”

Section: Methods For the Nanogap Characterizationmentioning

confidence: 99%

“…174 Impedance spectroscopy was applied to rigorously characterize the nanogap-based electrical devices and predicted a model. 175 The parameters such as sensitivity to permittivity changes were also predicted by the model and compared with the measured values. 176 The detection limit of the different magnitude was found and the magnitude of the impedance (|Z|) was in the range of 100-0.2 MHz.…”

Section: Electrical Characterizationmentioning

confidence: 99%

Recent advances in techniques for fabrication and characterization of nanogap biosensors: A review

Adam

Dhahi

Gopinath

et al. 2021

Biotech and App Biochem

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Nanogap biosensors have fascinated researchers due to their excellent electrical properties. Nanogap biosensors comprise three arrays of electrodes that form nanometer-size gaps. The sensing gaps have become the major building blocks of several sensing applications, including bio-and chemosensors. One of the advantages of nanogap biosensors is that they can be fabricated in nanoscale size for various downstream applications. Several studies have been conducted on nanogap biosensors, and nanogap biosensors exhibit potential material properties. The possibilities of combining these unique properties with a nanoscalegapped device and electrical detection systems allow excellent and potential prospects in biomolecular detection. However, their fabrication is challenging as the gap is becoming smaller. It includes high-cost, low-yield, and surface phenomena to move a step closer to the routine fabrications. This review summarizes different feasible techniques in the fabrication of nanogap electrodes, such as preparation by self-assembly with both conventional and nonconventional approaches. This review also presents a comprehensive analysis of the fabrication, potential applications, history, and the current status of nanogap biosensors with a special focus on nanogap-mediated bio-and chemical sonsors.

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“…Quartz oscillators are widely used in sensor technology because of the stability of crystal oscillation [ 1 , 2 , 3 , 4 , 5 ]. Quartz crystals have a temperature dependence of a few ppm [ 6 , 7 , 8 , 9 , 10 ] which can be significantly reduced (compensated) by using two equal oscillators and two crystals, which form a temperature pair.…”

Section: Introductionmentioning

confidence: 99%

Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors

Matko

2023

Sensors

Self Cite

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We proposed a method for measuring frequency differences of the order of a few Hz with an experimental error lower than 0.0001% by using two 4 MHz quartz oscillators, the frequencies of which are very close (a few 10 Hz difference) due to the dual mode operation (differential mode with two temperature-compensated signal frequencies or a mode with one signal and one reference frequency). We compared the existing methods for measuring frequency differences with the new method which is based on counting the number of transitions through zero within one beat period of the signal. The measuring procedure requires equal experimental conditions (temperature, pressure, humidity, parasitic impedances etc.) for both quartz oscillators. To ensure equal resonant conditions for oscillation two quartz crystals are needed, which form a temperature pair. The frequencies and resonant conditions of both oscillators must be almost equal, which is achieved by an external inductance or capacitance. In such a way, we minimized all the external effects and ensured highly stable oscillations and high sensitivity of the differential sensors. The counter detects one beat period by an external gate signal former. By using the method of counting transitions through zero within one beat period, we reduced the measuring error by three orders of magnitude, compared to the existing methods.

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Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

Cited by 8 publications

References 34 publications

Electrical Impedance-Based Characterization of Hepatic Tissue with Early-Stage Fibrosis

Electrical Impedance-Based Characterization of Hepatic Tissue with Early-Stage Fibrosis

Recent advances in techniques for fabrication and characterization of nanogap biosensors: A review

Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors

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