Square-wave Frequency Research Articles

Single-Walled Carbon Nanotube-Reinforced PEDOT: PSS Hybrid Electrodes for High-Performance Ionic Electroactive Polymer Actuator

Ionic electroactive polymer (iEAP) actuators are recognized as exceptional candidates for artificial muscle development, with significant potential applications in bionic robotics, space exploration, and biomedical fields. Here, we developed a new iEAP actuator utilizing high-purity single-walled carbon nanotubes (SWCNTs)-reinforced poly(3, 4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT: PSS, PP) hybrid electrodes and a Nafion/EMIBF4 ion-exchange membrane via a straightforward and efficient spray printing technique. The SWCNT/PP actuator exhibits significantly enhanced electric conductivity (262.9 S/cm) and specific capacitance (22.5 mF/cm2), benefitting from the synergistic effect between SWCNTs and PP. These improvements far surpass those observed in activated carbon aerogel bucky-gel-electrode-based actuators. Furthermore, we evaluated the electroactive behaviors of the SWCNT/PP actuator under alternating square-wave voltages (1–3 V) and frequencies (0.01–100 Hz). The results reveal a substantial bending displacement of 6.44 mm and a high bending strain of 0.61% (at 3 V, 0.1 Hz), along with a long operating stability of up to 10,000 cycles (at 2 V, 1 Hz). This study introduces a straightforward and efficient spray printing technique for the successful preparation of iEAP actuators with superior electrochemical and electromechanical properties as intended, which hold promise as artificial muscles in the field of bionic robotics.

Sensorless Control With Switching Frequency Square Wave Voltage Injection for SPMSM With Low Rotor Magnetic Anisotropy

High-frequency signal injection sensorless algorithms are widely studied and used for rotor angle estimation in PMSM at low speed or standstill. One of the main drawbacks of such methods is the acoustic noise connected to the voltage injection. In order to minimize this problem, it is advisable to increase the frequency of the injected signal. Thus, many studies focus on square-wave injection at the switching frequency, which is the maximum theoretical frequency. Since these methods exploit the rotor magnetic anisotropy, it is relatively easy to use them in interior PMSMs, where the rotor anisotropy is high. On the contrary, it is hard to exploit them in surface PMSMs, which have an almost symmetric rotor, although a low rotor magnetic anisotropy is still present. In this paper, a sensorless algorithm with switching frequency square-wave injection is developed for surface PMSMs. To increase the signal-to-noise ratio, current oversampling is exploited. The benefits of such a technique are demonstrated with experimental results on a 2 Nm SPMSM.

Quantification of dermis sodium concentration in skin layers by power spectral density drop of square-wave electrical impedance spectroscopy (PSDd-sEIS)

Assessing dermis sodium concentration in skin is essential since an excessive amount of sodium is associated with vascular function disorders. In this research, dermis sodium concentration has been quantified by the power spectral density drop of square-wave electrical impedance spectroscopy (PSDd-sEIS). PSDd-sEIS is composed of three stages: (1) dermis voltage measurement, (2) PSDd calculation, and (3) dermis sodium quantification. In the 1st stage, three electrodes are arranged to measure voltage under the constant current of square-wave. In the 2nd stage, is evaluated by the first and third harmonic frequency from . In the 3rd stage, is quantified by the developed linear regression. To obtain the highest sensitivity between c and four measurement factors (square-wave frequency duty-cycle , electrode distance d, and electrode diameter ø) were optimized using numerical simulations of a skin model. Experiments on multi-layered skin under various c in the range of 5 nM–50 mM were conducted by PSDd-sEIS hardware with optimized measurement factors of , , , and . As the results, the quantification of c has a good accuracy with the normalized sensitivity =0.87 and determination coefficient R2 = 0.92. The measurement factors of and affect the power of square-wave excitation to pass through the high resistivity barrier of the stratum corneum, while the measurement factors of d and ø affect the stability of current flow in the dermis.

MODERNIZATION OF THE KHARKIV MICROWAVE SPECTROMETER: CURRENT STATE

Subject and Purpose. Results are presented of the recent considerable upgrade implemented at the Kharkiv microwave spectrometer. The upgrade has been aimed at extending the operating frequency range and increasing the utmost accessible spectral resolution of the spectrometer. Methods and Methodology. In order to extend the frequency range we have designed and constructed new BWO-based oscillator units, also providing for possibility of frequency tripler application. Construction of a new absorbing cell of enlarged diameter allowed us to considerably improve the spectral resolution for Lamb-dip measurements. Results. Owing to the upgrade, the spectrometer has become able to cover the frequency range from 34 to 420 GHz, with a gap from 183 to 200 GHz. The spectral resolution in the Lamb-dip observation mode has been increased by a factor of two. In addition, the functionality of the spectrometer has been significantly improved via modernization of several of its subsystems. Conclusions. The new upgrades of the spectrometer systems have permitted extending the operational frequency range and increasing the utmost accessible resolution by means of reducing the time-of-flight line broadening in the Lamb-dip measurements. In addition, application of square-wave frequency modulation with accurately known modulation parameters, in combination with careful modeling of the distortions caused by reflections in the absorbing cell, has allowed us to significantly improve the accuracy of line frequency measurements.

The Effect of Mechanical Frequency on Piezoelectrochemical Energy Harvesters.

Microenergy harvesters such as piezoelectro-chemical (PEC) devices allow the extraction of low-frequency mechanical energy, which might otherwise be lost. Recent literature on PEC harvesters has noted that the input mechanical frequency affects the device current outputs, but this effect is not well understood. Mechanical energy sources often have variable frequencies, so understanding PEC harvester performance as a function of frequency is vital for the optimization of these devices. Using a commercially available lithium ion pouch cell as a test system, this work finds that applying a square-wave frequency with the fastest strain rate and longest hold time maximizes PEC current output. There is a monotonic increase in peak power, maximum half-cycle energy, and energy conversion efficiency as the input mechanical frequency approaches zero. This indicates that PEC harvesters have more flexibility in operating frequency than piezoelectric harvesters, as PEC harvesters do not have resonance or antiresonance frequencies.

SQUARE-WAVE FREQUENCY MODULATION IN MICROWAVE SPECTROSCOPY

Subject and Purpose. The frequency modulation (FM)combined with lock-in detection, the technique which is used in microwave spectroscopy for enhancing the sensitivity of measurements, as well as the effects due to standing wavesinthe measuring absorption cell can lead to distortions in the spectral line shapes observed. To ensure the highest possible accuracy derivable from the experimental data, these distortions needto be taken into account. A way of improving theaccuracy is to approximate to the experimental line contour with a theoretical line shape that would account for the observable distortion effects.The relevant literature sources suggest examples of theoretical expressions for the line shape in the case of a sinusoidal frequency modulation. This work has been aimed at derivingsimilar expressions for the case of a square-wave frequency modulation that shall allow increasing the accuracy of measurements. Methods and Methodology.The square-wave-FM signalsare obtained with the aid of a direct digital frequency synthesizer thatcan provide switching between two frequencies known to a high accuracy. This technical solution permits generating FM signals with precisely specified parameters. Results. A closed-form expression has been suggested, based on numerically evaluated line shape derivatives, whichallows taking into considerationthe basic types of distortions encountered in the spectral line records. The cases that have been considered concern a variety of experimental conditions, including sub-Doppler measurements with Lamb-dip observations. Conclusions. The approach that has been proposed allows one to properly take into account the distortions of spectral line shapes resulting from the use of a square-wave-FM signal, as well as those due to standing wave effects in the spectrometer cell. As has been found, application of this approach to experimental spectra with a variety of modulation parameters permits reducing the errors of frequency determination to ±0.001MHz, provided the signal-to-noise ratios are reasonably high.

Mechanistic analysis of the cathodic stripping square-wave voltammetric response of the copper‑arsenic system at a mercury electrode

Despite arsenite can be reduced to As(0) and deposited at the surface of solid electrodes such as gold, platinum, or copper, it cannot form amalgams with mercury, and so the addition of other metal ions is required for its deposition. In this manuscript, mechanistic analysis of the cathodic stripping square-wave voltammetric response of the system copper‑arsenic is presented. For the analysis of experimental responses, a mathematical model is used to consider that a surface-active reagent undergoes a charge transfer step followed by a chemical reaction. The dependences of the differential peak current, and the respective peak potential and half-peak width on the square-wave frequency were used to estimate the apparent stability constant of arsenide formation and that the electrode reaction would involve the direct transfer of 2 electrons, while the simulation and fit of forward and backward voltammetric responses have been useful for inferring other parameters such as the formal charge transfer rate constant of the global electron transfer reaction, a pseudo-first order homogeneous rate constant associated with arsenide formation, and the charge transfer coefficient of the global electron transfer reaction. Besides the values estimated for each of those parameters, all simulations indicate that the reduction of copper instead of arsenic would be taking place during the cathodic stripping scan. Accordingly, the trace-analysis reaction of arsenic in the presence of copper would be based on the surface accumulation of a metal complex, where Cu 2+ would be the metal cation and an arsenide species the ligand. The stability of that complex at the surface of a mercury electrode would depend not only on the applied potential, but also on the ratio between copper, arsenic, and protons. • Mechanistic analysis of the CS-SWV response of the system copper-arsenic is presented. • This is the first time that a mathematical model of such complexity is used for simulating experimental voltammograms. • The simulation and fit of the experimental curves are step-by-step described. • Simulations indicate that the reduction of Cu(II) instead of As(0) takes place during the cathodic stripping scan. • A surface analysis is required when the scan-rate affect the apparent reversibility of more than one kinetic constant.

High Frequency Square-Wave Voltage Injection Scheme-Based Position Sensorless Control of IPMSM in the Low- and Zero- Speed Range

In this paper, a new sensorless control scheme with the injection of a high-frequency square-wave voltage of an interior permanent-magnet synchronous motor (IPMSM) at low- and zero-speed operation is proposed. Conventional schemes may face the problems of obvious current sampling noise and slow identification in the process of magnetic polarity detection at zero speed operation, and the effects of inverter voltage error on the rotor position estimation accuracy at low speed operation. Based on the principle analysis of d-axis magnetic circuit characteristics, a method for determining the direction of magnetic polarity of d-axis two-opposite DC voltage offset by uninterruptible square-wave injection is proposed, which is fast in convergence rate of magnetic polarity detection and more distinct. In addition, the strategy injects a two-opposite high-frequency square-wave voltage vectors other than the one voltage vector into the estimated synchronous reference frame (SRF), which can reduce the effects of inverter voltage error on the rotor position estimation accuracy. With this approach, low-pass filter (LPF) and band-pass filter (BPF), which are used to obtain the fundamental current component and high-frequency current response with rotor position information respectively in the conventional sensorless control, are removed to simplify the signal process for estimating the rotor position and further improve control bandwidth. Finally, the experimental results on an IPMSM drive platform indicate that the rotor position with good steady state and dynamic performance can be obtained accurately at low-and zero-speed operation with the sensorless control strategy.

Design and Implementation of a Novel Tilt Sensor Based on the Principle of Variable Reluctance.

Tilt angle measurement in dynamic systems is problematic because the rotation of the measured platform is coupled with translation. Therefore, when some sensors are applied in dynamic systems, their output signals are often submerged in the noise signals generated by translation. To enhance the ability of tilt sensors to resist translational noise, a dynamic tilt sensor is proposed based on the principle of variable reluctance from the perspective of sensor structure. The eccentric structure of the sensor constructed with a shell, liquid, and internal damping plate was designed according to the principles of mechanics. The characteristic of translational acceleration restraint determined by the sensor structure was established theoretically. In addition, the magnetic circuit of the sensor was analyzed to illustrate the sensor’s working principles. A Clapp oscillator circuit was designed to convert mechanical motion into a measureable electrical signal. A method to determine the sensor’s direction of rotation is proposed. A waveform conversion circuit was designed to convert the sine wave output of the Clapp oscillator to a square wave, and a square-wave frequency measurement circuit was designed based on the C8051 micro-control unit. A translation–rotation experimental hardware platform was constructed. The data acquisition program was designed on a PC platform, and the translation–rotation experiments were conducted with an MTi attitude measurement unit as a reference. The validity of the tilt angle measurements and the effect of the translational acceleration restraint of the sensor were verified by the experimental data. The theoretical results obtained were consistent with the experimental data, verifying the validity of the theoretical analysis and experimental devices employed. A measurement range of −180 to 180° was achieved.

Research on nozzle and needle combination for high frequency piezostack-driven dispenser

An on-off valve piezostack-driven dispenser is used as a study object to investigate the influence of the needle and nozzle combination on the high frequency jetting. Firstly, the jetting dispensing process and fluid dynamics are studied. Secondly, FLOW-3D software is used to model and simulate the needle and nozzle with different mating angles of sphere-sphere, sphere-short cone, sphere-short cone and cone-cone. The operating performances of different matching forms are compared and summarized according to the simulation results. Thirdly, the designed spherical-spherical needle and nozzle with 180° are grinded and installed on the dispenser, and the experiment system is built. By using a glycerol/alcohol mixture with a viscosity of 180 cP, we can realize the industrial frequency of 360 Hz in droplet continuous dispensing, and the average diameter of droplets is 525 μm. Moreover, the viscosity of 800 cP industrial epoxy resin form droplets have good geometry. under the conditions of nozzle diameter of 100 μm and square-wave frequency of 320 Hz, the variation of the droplet diameter is within ±2%. The findings in this paper can guide the design of nozzle and needle for jetting dispenser, which is used to meet specific industrial requirements.

Seconds-resolved pharmacokinetic measurements of the chemotherapeutic irinotecan in situ in the living body.

The ability to measure drugs in the body rapidly and in real time would advance both our understanding of pharmacokinetics and our ability to optimally dose and deliver pharmacological therapies. To this end, we are developing electrochemical aptamer-based (E-AB) sensors, a seconds-resolved platform technology that, as critical for performing measurements in vivo, is reagentless, reversible, and selective enough to work when placed directly in bodily fluids. Here we describe the development of an E-AB sensor against irinotecan, a member of the camptothecin family of cancer chemotherapeutics, and its adaptation to in vivo sensing. To achieve this we first re-engineered (via truncation) a previously reported DNA aptamer against the camptothecins to support high-gain E-AB signaling. We then co-deposited the modified aptamer with an unstructured, redox-reporter-modified DNA sequence whose output was independent of target concentration, rendering the sensor's signal gain a sufficiently strong function of square-wave frequency to support kinetic-differential-measurement drift correction. The resultant, 200 μm-diameter, 3 mm-long sensor achieves 20 s-resolved, multi-hour measurements of plasma irinotecan when emplaced in the jugular veins of live rats, thus providing an unprecedentedly high-precision view into the pharmacokinetics of this class of chemotherapeutics.

Experimental study on bi-directional friction linear micro-motor driven by a set of micro-actuator

ABSTRACTThis paper presents a bi-directional friction linear micro-motor (BFLM), which is driven by a set of micro-actuator through friction drive. The BFLM has been fabricated using PolyMUMPs process. The forward and backward movement displacement, velocity and acceleration of the slider are measured. Movement velocities of the slider can be controlled by changing the driving frequency. It is feasible to use one set of actuator to driving the slider bidirectional motion. The BFLM is operated at square-wave frequencies with 38.39 kHz to get the maximum displacement of 100 µm and the average velocities are 10.709 µm/s in forward movement and 10.321 µm/s in backward movement.

Design and implementation of a low cost photovoltaic soil moisture monitoring station for irrigation scheduling with different frequency domain analysis probe structures

Frequency Domain Analysis (FDA), as an approach, has been developed for the measurement of soil dielectric constants. As it stands, the standard dielectric of dry soil is much less than the dielectric of soil exposed to water, and the volume of water present significantly affects the propagation of electromagnetic waves. With this in mind, this paper proposes a plan for the design and implementation of two distinct isolated probe structures for the measurement of water contents within the soil at different levels. Accordingly, Probe A is used to determine the water level present in soil at four different depths. Probe A does this by utilizing pairs of parabolic copper sections fixed horizontally and isolated over the outer surface of an access tube. Probe B, on the other hand, makes use of two steel rings buried vertically inside of an access tube, and is used to determine the water contents of soil on two levels. To do so, a fixed frequency square-wave is transmitted to measure the soil capacitance in which the probe sensors are connected to an Arduino microcontroller which also included air humidity, air temperature, and soil temperature sensors. During the experimental assessment of both probes, the results are loaded onto an SD memory card and are then compared with the results of other commercial sensors installed in the same irrigated plot. The soil moisture monitoring station used is powered by a photovoltaic (PV) module of 10 W 12 V and a storage battery of 12 Ah. The experimental monitoring station used to assess the efficiency of both probe designs was set up in a Mediterranean semiarid zone in the Southeast of Spain.

Calibration-Free Electrochemical Biosensors Supporting Accurate Molecular Measurements Directly in Undiluted Whole Blood.

The need to calibrate to correct for sensor-to-sensor fabrication variation and sensor drift has proven a significant hurdle in the widespread use of biosensors. To maintain clinically relevant (±20% for this application) accuracy, for example, commercial continuous glucose monitors require recalibration several times a day, decreasing convenience and increasing the chance of user errors. Here, however, we demonstrate a "dual-frequency" approach for achieving the calibration-free operation of electrochemical biosensors that generate an output by using square-wave voltammetry to monitor binding-induced changes in electron transfer kinetics. Specifically, we use the square-wave frequency dependence of their response to produce a ratiometric signal, the ratio of peak currents collected at responsive and non- (or low) responsive square-wave frequencies, which is largely insensitive to drift and sensor-to-sensor fabrication variations. Using electrochemical aptamer-based (E-AB) biosensors as our test bed, we demonstrate the accurate and precise operation of sensors against multiple drugs, achieving accuracy in the measurement of their targets of within better than 20% across dynamic ranges of up to 2 orders of magnitude without the need to calibrate each individual sensor.

Simultaneous voltammetric determination of carbendazim and carbaryl in medicinal plant infusions with a boron-doped diamond electrode

ABSTRACTThis study is aimed to develop an electroanalytical methodology using a boron-doped diamond electrode to determine simultaneously and selectively carbendazim (CBZ) and carbaryl (CAR). In previous studies using cyclic voltammetry oxidation, peaks were observed at 1.03 V (CBZ) and 1.44 V (CAR), with characteristics of an irreversible process controlled by diffusion of species, with a supporting electrolyte of BR buffer (0.1 mol L−1) and pH adjusted to 6.0. The differences between the potentials for both pesticides, about 400 mV, indicate the possibility of selective determination of CBZ and CAR. The square-wave voltammetric parameters were optimised. The best separation conditions were pH 6.0, square-wave frequency of 100 s−1, pulse amplitude of 50 mV and scan increment of 2.0 mV. These parameters were used to obtain the calibration curves of CBZ and CAR. An analytical curve was constructed in the range concentration of CBZ of 1.3 mg L−1 to 15.3 mg L−1 and CAR of 1.0 mg L−1 to 11.4 mg L−1, respectively. The limits of detection (LOD) and limits of quantification (LOQ) for CBZ were 0.40 mg L−1 and 1.30 mg L−1, respectively. For CAR, the LOD and LOQ were 0.30 mg L−1 and 1.00 mg L−1, respectively. Sensitivity values were 0.78 and 2.60 µA/mg L−1 for CBZ and CAR, respectively. The electroanalytical method was applied in Mikania glomerata infusions. The recovery values were 106.2% and 116.5% for CBZ and CAR, respectively. The results show that the developed method is suitable for application in medicinal plant samples.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Maximizing the Signal Gain of Electrochemical-DNA Sensors.

Electrochemical DNA (E-DNA) sensors have emerged as a promising class of biosensors capable of detecting a wide range of molecular analytes (nucleic acids, proteins, small molecules, inorganic ions) without the need for exogenous reagents or wash steps. In these sensors, a binding-induced conformational change in an electrode-bound "probe" (a target-binding nucleic acid or nucleic-acid-peptide chimera) alters the location of an attached redox reporter, leading to a change in electron transfer that is typically monitored using square-wave voltammetry. Because signaling in this class of sensors relies on binding-induced changes in electron transfer rate, the signal gain of such sensors (change in signal upon the addition of saturating target) is dependent on the frequency of the square-wave potential pulse used to interrogate them, with the optimal square-wave frequency depending on the structure of the probe, the nature of the redox reporter, and other features of the sensor. Here, we show that, because it alters the driving force of the redox reaction and thus electron transfer kinetics, signal gain in this class of sensors is also strongly dependent on the amplitude of the square-wave potential pulse. Specifically, we show here that the simultaneous optimization of square-wave frequency and amplitude produces large (often more than 2-fold) increases in the signal gain of a wide range of E-DNA-type sensors.

Research and data processing of double locked cavity ringdown absorption spectroscopy

A continuous wave cavity ringdown spectroscopy based on a double-locking loop is proposed to improve the shortcoming of low acquisition rate of concentration in traditional scheme. A small portion of laser is separated to pass through a C2H2 reference cell, used to lock the laser frequency to the 1+3 band P(9)e absorption line of C2H2 at 6534.3634 cm-1 by the 1st harmonic demodulation of the frequency modulation spectroscopy. The remaining portion is incident on a high finesses cavity to observe the ringdown events. Meanwhile, the reflected light of cavity is used to extract the error signal to lock the laser based on the PDH frequency locking technique. As a consequence, the frequency drift of the laser and the jitter of the cavity length are improved, therefore a more relatively accuracy result is expected. The laser light is dual frequency modulated by a fiber coupled electro optic modulator (FEOM)in the above system. In order to optimize, to some extent, the asymmetry of the error signal caused by the residual amplitude modulation due to the inconsistency of the laser polarization direction with the extraordinary axis of the FEOM, the demodulation phase is adjusted carefully until the error signal is smoothed up and close to symmetry. Then, the effect of locking loop is examined. The frequency of laser, based on the measurement by a wavelength meter, is more stable and the relative frequency discrimination between the laser and the longitudinal mode of cavity is about 9.8 kHz. In addition, the PDH locking, ensuring the efficient coupling of the laser with the cavity, can gain a high acquisition rate of the concentration information. In order to obtain a complete ringdown event, the frequency of square wave to the fiber coupled acoustic optical modulator (FAOM) is limited to 30 kHz with the duty cycle of 85%, which is determined by the ringdown time and re-lock time. However, there exists a relatively large random noise in a series of ringdown time measurements of empty cavity, which is mainly caused by the errors of fitting and measurement. For the further improvement of the accuracy of experiment, an efficient digital filter, Kalman filter which can suppress the noise considerably at no expense of real-time capability, is used. The standard deviation of the ringdown time is reduced from 0.00333 to 0.00153. According to Allan variance analysis, the detection limit can reach 410-9 cm-1 for a 2 s integration time. Finally, the C2H2 gases with different concentrations from 100 ppb to 5 ppm are measured to demonstrate the linear response of this system.

A Novel Compact Repetitive Frequency Square-Wave Generator Based on Coaxial Pulse Forming Lines and Coupled Magnetic Switches

In this paper, a novel repetitive frequency square-wave generator named pulse forming line-based repetitive square-wave generator (PFLRSG)-based coaxial pulse forming lines (PFLs) and coupled magnetic switches (MSs) is proposed. The generator is capable of amplitude multiplication, high-frequency operation, and rise-time compression. The operation principle is to charge PFLs in parallel via coupled inductors when MSs are unsaturated and discharge in series when MSs saturate to form square-wave voltage pulses across the matched load, with the common diode arrays as the last stage to sharpen the rise-time. The amplitude of the output pulse is dependent on the charging voltage and impedance matching between the PFLs and the load. The pulsewidth is determined by the transmission time of the PFLs. With the principle, circuit topology of a two-stage PFLRSG is presented. Test stand yields an output square-wave pulse with frequency of 1-10 kHz, amplitude of 8.6 kV, rise-time of 60 ns, and half width of 500 ns into a 150-Ω matched load. Furthermore, design rules are proposed so that topologies of PFLRSGs with stages other than two can be conveniently derived. As an example, a 4-stage PFLRSG is proposed.

Integrated Square Wave Voltammetry Redox Sensor System for Electrochemical Analysis

An integrated square wave voltammetry (SWV) redox sensor has been developed on the basis of a standard complementary metal–oxide–semiconductor (CMOS) process technology. The sensor consists of a square wave (SW) pulse generator, a voltage controller, and two electrodes for electrochemical analysis. Our proposed sensor is the first integrated sensor system of a SW pulse generator. Potassium ferricyanide solution was measured to obtain the characteristics of the proposed sensor. We confirmed that the dynamic ranges of potassium ferricyanide concentration and SW frequency were obtained from 0.6 to 6 mM and from 20 to 500 Hz, respectively. To verify the accuracy of the proposed sensor system, we performed a comparison between the fabricated sensor and an electrochemical analyzer.