Design and Characterization of a Passive Wireless DNA Sensor

This paper presents a concept for a passive wireless DNA sensing platform that exploits a multidisciplinary area, synthesizing the conventional DNA capacitive sensing mechanism and the surface-based conformational characterization throughout DNA immobilization and hybridization. The resonant frequency shift, caused by the change of capacitance throughout DNA immobilization and hybridization and occurring on top of an interdigital capacitor, is monitored by means of an impedance analyzer. 32 samples were measured throughout the experiment and the average capacitance measurements represented a variety of surface charges resulting from DNA molecule immobilization and hybridization. The capacitance changed from 11.58 pF to 114.5 pF when specific ssDNA was attached to electrodes and then increased to 218.6 pF once complementary strand DNA was introduced and hybridized with existing DNA chains. In addition, using impedance analyzer measurements, the resonant frequency decreased from 2.01 MHz to 1.97 MHz in the presence of ssDNA and decreased further down to 0.95 MHz after the complementary strand DNA was deposited.

Investigation of electromechanical impedance and residual stress relation for samples machined by hot ultrasonic-assisted turning

Electromechanical impedance (EMI) method has been widely used in recent years to evaluate the condition of structures. In this method, piezoelectric sensors are added to the structure to examine material properties. The impedance/admittance signals are recorded with the aid of the impedance analyzer without any conversion. When there is any change in structures, differences occur in these signals. Thus, changes in structures can be easily determined. It is known that residual stress plays a vital role in materials in terms of crack initiation, breakage, fatigue life, etc. In contrast, the detection of residual stress is time-consuming and it requires experience. This study reveals the effect of cutting parameters on residual stress and electromechanical impedance/admittance values. Firstly, hot ultrasonic-assisted turning was performed for Ti6Al4V material. A parametric study was carried out with different cutting depth, feed rate, and cutting speed. In the second stage, residual stress values measured by X-Ray diffraction (XRD) method and impedance/admittance values measured by an impedance analyzer were compared. In this context, empirical equations with their values between stress/impedance–admittance values have been derived. In general, it has been observed that stress values are significantly associated with impedance/admittance values and the highest correlation was obtained with the reactance values.

Validation of Low-Cost Impedance analyzer via Nitrate Detection

Impedance spectroscopy is a widely used electrochemical technique with a wide variety of applications. Many of these applications benefit from the additional accessibility provided by low-cost impedance devices. With this in mind, a low-cost impedance device was designed for a high performance-to-cost ratio. The performance of this analyzer was validated against a high-performance DropSens µStat-i 400s potentiostat by performing an application-based experiment. Nitrate detection provides a relevant experiment because of the importance of maintaining precise nitrate concentrations to mitigate the impact of nitrate fluctuations on the environment. Dissolved nitrate samples of different concentrations, in the range 3–1000 mg/L, were confirmed colorimetrically and measured with both instruments. A calibration curve of the real impedance matched a sigmoidal transfer, with a linear region for concentrations below 10 mg/L. The device under investigation exhibited an average magnitude error of 1.28% and an average phase error of 0.96∘ relative to the high-performance standard, which validates the performance of the low-cost device. A cost analysis is presented that highlights some of the complexities of cost comparisons.

Point-of-care microvolume cytometer measures platelet counts with high accuracy from capillary blood

Background Point-of-care (PoC) testing of platelet count (PLT) provides real-time data for rapid decision making. The goal of this study is to evaluate the accuracy and precision of platelet counting using a new microvolume (8 μL), absolute counting, 1.5 kg cytometry-based blood analyzer, the rHEALTH ONE (rHEALTH) in comparison with the International Society of Laboratory Hematology (ISLH) platelet method, which uses a cytometer and an impedance analyzer. Methods Inclusion eligibility were healthy adults (M/F) ages 18–80 for donation of fingerprick and venous blood samples. Samples were from a random N = 31 volunteers from a single U.S. site. Samples were serially diluted to test thrombocytopenic ranges. Interfering substances and conditions were tested, including RBC fragments, platelet fragments, cholesterol, triglycerides, lipids, anti-platelet antibodies, and temperature. Results The concordance between the rHEALTH and ISLH methods had a slope = 1.030 and R2 = 0.9684. The rHEALTH method showed a correlation between capillary and venous blood samples (slope = 0.9514 and R2 = 0.9684). Certain interferents changed platelet recovery: RBC fragments and anti-platelet antibodies with the ISLH method; platelet fragments and anti-platelet antibodies on the rHEALTH; and RBC fragments, platelets fragments, triglycerides and LDL on the clinical impedance analyzer. The rHEALTH’s precision ranged from 3.1–8.0%, and the ISLH from 1.0–10.5%. Conclusions The rHEALTH method provides similar results with the reference method and good correlation between adult capillary and venous blood samples. This demonstrates the ability of the rHEALTH to provide point-of-care assessment of normal and thrombocytopenic platelet counts from fingerprick blood with high precision and limited interferences.

Modeling and Measurements of Properties of Coupled Inductors

This paper proposes a model of a coupled inductor which takes into account the influence of frequency, temperature, and a constant component, IDC, of currents in the windings on the parameters of the considered element. A description of the model and methods of measuring parameters of the inductor using an impedance analyzer and a chamber for thermal measurements is given. The obtained results of measurements are compared with the results of calculations proving a satisfactory match.

The Effects of Potentiostat Scan Rate Variation on Impedance Value, Topography, and Morphology of the Polyaniline Thin Film

The effects of potentiostat scan rate on the impedance, topography, and morphology of the Polyaniline (PANi) thin film has observed in this study. PANi has deposited on the Quartz Crystal Microbalance (QCM) surface with various scan rates, and changes in the impedance value have observed through an impedance analyzer test. Topography Measurement System (TMS) has observed the layer topography, while the layer morphology has observed using optical microscopy and Scanning Electron Microscope (SEM). The results have shown that the best sample has a scan rate of 10 mV/s, with a low impedance value indicating the layer has rigid. The variation in scan rate can affect the impedance value, but it is not significant and does not indicate a damping effect on QCM. A homogeneous layer is deposited at a low scan rate from topography and morphological observations, while a high scan rate results in an inhomogeneous layer.