Sensitivity Of Transducer Research Articles

Imperceptible energy harvesting device and biomedical sensor based on ultraflexible ferroelectric transducers and organic diodes

Energy autonomy and conformability are essential elements in the next generation of wearable and flexible electronics for healthcare, robotics and cyber-physical systems. This study presents ferroelectric polymer transducers and organic diodes for imperceptible sensing and energy harvesting systems, which are integrated on ultrathin (1-µm) substrates, thus imparting them with excellent flexibility. Simulations show that the sensitivity of ultraflexible ferroelectric polymer transducers is strongly enhanced by using an ultrathin substrate, which allows the mounting on 3D-shaped objects and the stacking in multiple layers. Indeed, ultraflexible ferroelectric polymer transducers have improved sensitivity to strain and pressure, fast response and excellent mechanical stability, thus forming imperceptible wireless e-health patches for precise pulse and blood pressure monitoring. For harvesting biomechanical energy, the transducers are combined with rectifiers based on ultraflexible organic diodes thus comprising an imperceptible, 2.5-µm thin, energy harvesting device with an excellent peak power density of 3 mW·cm−3.

Evaluating the impact of acoustic impedance matching on the airborne noise rejection and sensitivity of an electrostatic transducer

To capture sound from solid mediums, such as the human body or musical instruments, transducers designed for airborne sound pickup are typically used. Acoustic impedance mismatches between the medium and transducer decrease the energy captured and increase noise corruption. Here, we demonstrate the improved sensitivity and airborne noise rejection of an electrostatic transducer with an acoustic impedance matched to the medium of interest. The transducer produces an electrical response when mechanical vibrations compress the distance between an elastomer with patterned microstructures and a charged electret film. Using a statistical model generated through an I-optimal design of experiments, the elastomer is fabricated with a specific polymer and concentration of nanoparticles to possess a targeted acoustic impedance. Transducers containing elastomers with impedances in the range of 1 to 2.2 MRayls are assembled and characterized on simulators emulating the human body and a wooden instrument. The noise rejection is quantified using the coherence between the captured transducer signal and the simulated ambient noise. Sensitivities are similarly characterized by comparing the transducer signal and input simulator signal. With an impedance closely matched to the medium of interest, the transducer demonstrates a 2V/N sensitivity and 35 dB SNR improvement compared to an airborne transducer.

NOISE INFLUENCE ON THE RESOLUTION OF THE SENSORS BASED ON MAGNETIC TRANSISTOR STRUCTURES

Absolute sensitivity is a parameter that directly connects the disturbing value with the response to it, is the determining physical characteristic of the absolute majority of the conversion structure, regardless on the operation principle. This parameter is also considered the main criterion for the quality of the product when using such structures as sensors of the corresponding values. Therefore, the problem of the transducer sensitivity increasing remains relevant in connection with the increasing the sensor number built on new principles: new materials, new functionality and increasing the requirements arising from the sensor operating conditions.

Boosting Selectivity and Sensitivity to Biomarkers of Quantum Resistive Vapour Sensors Used for Volatolomics with Nanoarchitectured Carbon Nanotubes or Graphene Platelets Connected by Fullerene Junctions

Nanocarbon-based vapour sensors are increasingly used to make anticipated diagnosis of diseases by the analysis of volatile organic compound (VOC) biomarkers from the breath, i.e., volatolomics. However, given the tiny number of molecules to detect, usually only tens of parts per billion (ppb), increasing the sensitivity of polymer nanocomposite chemoresistive transducers is still a challenge. As the ability of these nanosensors to convert the interactions with chemical compounds into changes of resistance, depends on the variations of electronic transport through the percolated network of the conducting nanofillers, it is a key parameter to control. Actually, in this conducting architecture, the bottlenecks for electrons’ circulation are the interparticular junctions giving either ohmic conduction in the case of close contacts or quantum tunnelling when jumps though gaps are necessary. This in turn depends on a number of nanometric parameters such as the size and geometry of the nanofillers (spherical, cylindrical, lamellar), the method of structuring of the conductive architecture in the sensory system, etc. The present study focuses on the control of the interparticular junctions in quantum-resistive vapour sensors (vQRS) by nanoassembling pristine CNT or graphene covalently or noncovalently functionalized with spherical Buckminster fullerene (C60) into a percolated network with a hybrid structure. It is found that this strategy allows us to significantly boost, both selectivity and sensitivity of pristine CNT or graphene-based transducers exposed to a set of seven biomarkers, ethanol, methanol, acetone, chloroform, benzene, toluene, cyclohexane and water. This is assumed to result from the spherical fullerene acting on the electronic transport properties at the nanojunctions between the CNT or graphene nanofillers.

Nanozymes “Artificial Peroxidase”: Enzyme Oxidase Mixtures for Single‐Step Fabrication of Advanced Electrochemical Biosensors

AbstractWe report the single‐step fabrication of advanced electrochemical biosensors upon drop‐casting of “artificial peroxidase”, that is, oxidase‐containing mixtures. Compared to bienzyme biosensors, we substitute peroxidase with more active and stable nanozymes based on catalytically synthesized Prussian Blue. The electroactivity of nanozymes in the sensing membrane was facilitated with carbon black nanoparticles, which resulted in record sensitivity of the H2O2 transducer exceeding 1.1 A M−1 ⋅ cm−2. Both glucose and lactate oxidases were co‐immobilized with nanozymes in alkoxysilane or perfluorosulfonated ionomer membranes. The proposed drop‐casting approach results in biosensors that are advantageous over those conventionally produced upon layer‐by‐layer immobilization in terms of i) almost an order of magnitude increased sensitivity, ii) unsurpassed biosensor‐to‐transducer sensitivity ratio reaching the value of 0.3, and iii) three times extended operational lifetime.

Study of transmission characteristics of disk transducer in the radially propagated Rayleigh wave excitation mode

A mathematical model of a capacitive ultrasonic transducer is designed allowing to emit ultrasonic vibrations into an electrically conductive product. The influence of a polarizing electrostatic field on the Coulomb forces formation in the surface layer of a metal sample is determined. A closed solution to the electrostatics problem is obtained for a piecewise homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. An expression is obtained for calculating the surface density of a static electric charge on the metal sample surface. As part of the mathematical model of a capacitive sensor in the mode of converting electric energy to high-frequency mechanical (ultrasonic) energy in metals, closed solutions for electrostatics and electrodynamics problems are constructed in relation to a piecewise-homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. It is determined that a capacitive disk transducer excites forces acting normally to the surface of electrically conductive products. A quantitative assessment of the surface density of the Coulomb forces is made. The main factors determining the sensitivity of a capacitive disk transducer are specified. As an example of using the simulation results, the amplitude factor of radially propagating Rayleigh waves is calculated. The concept of the wave characteristics of the transducer in the excitation mode of ultrasonic surface waves is introduced.

NVESTIGATION OF TRANSMISSION CHARACTERISTICS OF DISC CAPACITY CONVERTER IN THE MODE OF EXCITATION OF ULTRASOUND RELAY WAVES

A mathematical model of a capacitive ultrasonic transducer is designed allowing to emit ultrasonic vibrations into an electrically conductive product. The influence of a polarizing electrostatic field on the Coulomb forces formation in the surface layer of a metal sample is determined. A closed solution to the electrostatics problem is obtained for a piecewise homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. An expression is obtained for calculating the surface density of a static electric charge on the metal sample surface. The main influencing factors that determine the spatial distribution of the charge density on the product surface, which will form the radiation pattern and power of the emitted ultrasound field, are defined. As part of the mathematical model of a capacitive sensor in the mode of converting electric energy to high-frequency mechanical (ultrasonic) energy in metals, closed solutions for electrostatics and electrodynamics problems are constructed in relation to a piecewise-homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. It is determined that a capacitive disk transducer excites forces acting normally to the surface of electrically conductive products. A quantitative assessment of the surface density of the Coulomb forces is made. The main factors determining the sensitivity of a capacitive disk transducer are specified.

Inter-Stage Output Voltage Amplitude Improvement Circuit Integrated with Class-B Transmit Voltage Amplifier for Mobile Ultrasound Machines.

Piezoelectric transducers are triggered by the output voltage signal of a transmit voltage amplifier (TVA). In mobile ultrasound instruments, the sensitivity of piezoelectric transducers is a critical parameter under limited power supply from portable batteries. Therefore, the enhancement of the output voltage amplitude of the amplifier under limited power supply could increase the sensitivity of the piezoelectric transducer. Several-stage TVAs are used to increase the voltage amplitude. However, inter-stage design issues between each TVA block may reduce the voltage amplitude and bandwidth because the electronic components of the amplifier are nonlinearly operated at the desired frequency ranges. To compensate for this effect, we propose a novel inter-stage output voltage amplitude improvement (OVAI) circuit integrated with a class-B TVA circuit. We performed fundamental A-mode pulse-echo tests using a 15-MHz immersion-type piezoelectric transducer to verify the design. The echo amplitude and bandwidth when using an inter-stage OVAI circuit integrated with a class-B TVA circuit (696 mVPP and 29.91%, respectively) were higher than those obtained when using only the class-B TVA circuit (576 mVPP and 24.21%, respectively). Therefore, the proposed OVAI circuit could be beneficial for increasing the output amplitude of the class-B TVA circuit for mobile ultrasound machines.

Metrological Characteristics of Self-Oscillating Transducers for Track Control Systems

This is a study of the sensitivity and accuracy characteristics of three of the best known types of self-oscillating displacement transducers with flat screens which serve as contactless supports. The screens are made of different metals: cast iron, 45 and St3 steels, 12Kh18N10T stainless steel, brass, dural, and copper. The results of an experimental study are shown graphically and in tables taking into account the mutual position of the self-oscillating displacement transducers, as well as the operating conditions for these transducers as a function of the coordinates of the screens. It is shown that during operation of self-oscillating displacement transducers there is a hysteresis that increases on going from a diamagnetic to a ferromagnetic screen. Experiments show that the sensitivity of self-oscillating displacement transducers depends on the screen material. The effect of fluctuations in the supply voltage in the grid on the accuracy characteristics of self-oscillating displacement transducers is also studied and confirmed. The results of experimental studies can serve as useful reference data, and in a number of cases are necessary for specialists involved in the design of automated track control in various areas of machine building. Questions relating to the need for supply voltage stabilizers, the choice of screen material, etc., are discussed.

Electrical tuning for sensitivity enhancement of a piezo-electric ultrasonic transducer: Simulation and fabrication

In this study, two simple electrical impedance tuning methods derived from Krimholtz, Leedom, and Matthaei (KLM) modeling were proposed for increasing the sensitivity of a piezo-electric material-based ultrasonic transducer. In the first method, the reactance components of the ultrasonic transducer were removed, and in the other method, the electrical impedance of an ultrasonic transducer was matched to that of the ultrasonic system. To these ends, electrical circuits composed of inductors and capacitors were de-signed and KLM simulations of the two methods were performed. To verify the simulation results, ultrasonic transducers were fabricated and operated under the same conditions as in the simulations, and the experimental results were compared with the simulated results. In conclusion, the electrical tuning method (elimination of the reactance compo-nents) was more effective and the transducer circuit structure was simpler. The experi-mental results showed good agreement with the KLM simulation results.

Contactless galvano-magnetics transducers of monitoring and control systems in agricultural energy

The paper provides information on the state of the use of direct current energy in the electric power industry of agriculture and water resource, hydraulic engineering, industry and metallurgy, irrigation, and land reclamation. Identified the need for contactless non-destructive testing of large constant currents in high-power electrical installations in irrigation, land reclamation, and hydraulic engineering. The basic requirements for contactless transducers and meters of large direct currents in circuits without breaking them are shown. Identified priority areas in the development of these transducers. The general principles of constructing contactless ferromagnetic transducers of large direct currents also the basic requirements for them and the results of the development of one of the options for the development of effective innovative galvano-magnetic contactless transducers of large direct currents with an expanded range of monitoring and control systems for powerful pumping stations in water supply and land reclamation are presented. To increase the sensitivity of galvanomagnetic contactless transducers of large direct currents, Hall transducers have supplied with short-term rectangular current pulses from a special generator. When measuring the amplitude values of the rectified current, in this case of galvanomagnetic contactless transducers, the supply of pulses of the control current of the Hall transducers with the converted current in the bus synchronization is provided. This is achieved by supplying galvano-magnetic contactless transducers of large direct currents with a magnetically controlled contact located near the bus with the converted current and included in the circuit of the current electrodes of the Hall transducers.A static characteristic of the developed galvano-magnetic contactless transducer of high currents obtained and its main technical characteristics and parameters are given. It is shown that the developed transducer, unlike the known ones, has increased accuracy and sensitivity, a technological design, and low weight and dimensions at low material consumption and cost. It can be widely used in electrical systems in land reclamation and irrigation, in water supply, industry, rail transport, science, technology, and for checking electric meters at the installation site.

Single-polar power supply of high frequency capacitive transducers for measurement

It is possible to increase the sensitivity of capacitive ultrasonic transducers in three ways: increasing the capacitance of the transducer, increasing the polarizing and pulsed high-frequency voltage applied in the transducer cover, using modern methods of processing information packet pulses excited and received from the product. The increase in the capacity of the transducer is limited by the design capabilities of the transducer itself and the selection of the dielectric separating the plate from the surface of the electrically conductive testing object. Using modern methods of processing the received information significantly complicates and increases the cost of implementation of the device using a capacitive transducer. The most acceptable, at the moment, way to increase the sensitivity is to increase the power of high-frequency voltage supply generators provided that packet pulses are excited. The generator presented in the article allows to create pulsed peak voltages in low-capacitance transducers of more than 3 kV with frequencies up to 5 MHz with a duration of 1 period of the filling frequency and sounding frequencies up to 1 kHz. It was experimentally shown that using the prototype of a new generator, the amplitudes of the pulses transmitted through a steel sample 20 mm thick were obtained, the ratio of which to the noise amplitude received by the miniature piezoelectric transducer is 13 times. Using the developed powerful amplifier of voltage pulses will increase the amplitude of the pulses received from the transducer and repeatedly reflected in the product.

Advances in traceable calibration of cylinder pressure transducers

Accurate and reliable dynamic pressure measurements are needed for optimizing performance in modern combustion engines, manufacturing processes and aerospace applications. Besides fast pressure transients, these applications subject dynamic pressure transducers to elevated temperatures. Both of these quantities effect the sensitivity of transducers. Therefore, transducers should be calibrated at conditions that corresponds to the operating environment.To answer these needs, the National Metrology Institute VTT MIKES has developed its drop weight dynamic pressure primary standard further. Developments include improved control and measurement of the falling weight, extension of the pressure range to combustion engine pressures down to 3 MPa and a heating option for dynamic pressure transducers under calibration. These advances enable traceable calibration of cylinder pressure transducers at conditions relevant to engine applications. The overall uncertainty (k = 2) of calibration is estimated to be around 1.7%. The performance was demonstrated by calibrating a piezoelectric pressure transducer in the pressure and temperature range from 7 MPa to 30 MPa in 20 °C, 120 °C and 180 °C, respectively. As a result, traceable calibrations of dynamic pressure transducers can be performed at conditions relevant for engine applications. This improves the reliability and accuracy of in-cylinder pressure measurements.

Accuracy characteristics of autogenerator transducers for track control systems

The advantages of autogenerator displacement transducers in track control systems of metal – cutting machines, industrial robots, robotic complexes and flexible automated productions, such as high speed and durability of control systems, as well as their disadvantages-the lack of sufficiently complete accuracy characteristics, which affects the efficiency of equipment with track control systems, are considered. Formulated the research problem and described a special experimental setup, which studied the sensitivity of the self displacement transducers three types based on their mutual arrangement and screens of various metals (iron, steel 45, steel St3, 12KH18N10T steel, brass, dural and copper), as well as the conditions of their operation depending on the positioning of screens. The results of experimental data processing are presented, and any dependence of sensitivity on the screen material is not established. The assumption about the randomness and insignificance of the revealed differences is put forward and verified, and it is shown by the Cochran criterion that they are rightfully considered insignificant with a reliability of at least 95 %. The influence of power supply voltage fluctuations in the network on the accuracy characteristics of auto-generator displacement converters is studied and the results of the research are presented. A statistical test was carried out using the student’s criterion, which showed the absence of this influence on the accuracy characteristics. It is noted that hysteresis occurs during the operation of autogenerator displacement transducers and it is experimentally established that in most cases it increases with the transition from a diamagnetic screen to a ferromagnetic one. It is proposed to use the results of the research of precision characteristics in the design and efficient operation of the system limit control on the basis of self converters of displacements of the considered types, addressing issues about the need to use the voltage regulator when selecting screen material, etc.

Development of a high sensitive inductive movement sensor

Research on a contact induction displacement sensor over short distances is presented. A ferrite core with a winding and a movable armature is used as a sensor. There is an air gap between the core and the armature. To solve the problem of improving the accuracy of measurement, the sensor is included in the bridge measuring circuit, which is powered by high-frequency alternating current. To increase the sensitivity of the indicated sensor to movement, a differential circuit for its inclusion is proposed. Also, in order to increase sensitivity, the resonant mode of operation of the bridge measurement circuit is used. To maintain a constant voltage of the power generator, a phase-locked loop is used. As a result of the study of the induction displacement sensor, practical results were obtained with a maximum displacement of ±0.6 mm. The sensor has not been studied for large displacements, since with an increase in the indicated displacement, the nonlinearity of the displacement-current transformation appears. The maximum sensitivity of the differential sensor in the indicated range of movement 2.44 μA/μm is obtained without the use of a phase-locked loop. The use of a phase-locked-loop frequency adjustment system increased the sensitivity to 3.48 μA/μm. During the study, the dependence of the sensitivity of the sensor on the frequency of the power generator was determined, which allows to determine the optimal power frequency of the measuring bridge circuit. Studies have shown that the use of contact inductive meters have the prospect of application and reserves for improvement. And the use of differential inclusion of the sensor and the resonant mode of operation gives a significant increase in the sensitivity of the primary transducer at small displacements. An inexpensive sensor has been developed that will be useful for many applications where it is necessary to measure displacements and linear dimensions by contact methods

Differential diagnosis of focal gallbladder lesions: The added value of contrast enhanced ultrasound with liner transducers.

To evaluate the benefits of contrast-enhanced ultrasound (CEUS) with high frequency transducers in characterization of focal gallbladder lesions (FGL). From January 2017 to April 2019, 59 FGL detected by B mode ultrasound (BMUS) were examined, first with the low frequency convex transducer (1-5 MHz) and afterwards with high frequency transducer (7.5-12 MHz). High frequency dynamic CEUS were applied after bolus injection of 4.8 ml Sulphur hexafluoride microbubbles (SonoVue®, Milan). The BMUS and CEUS imaging features were recorded and compared. All lesions were confirmed by surgical resection and histopathologic results. The final diagnoses of 59 FGL included gallbladder adenocarcinoma (n = 15), gallbladder polyps (n = 11), gallbladder adenomas (n = 18), focal adenomyomatosis (n = 9), and gallbladder Ascariasis debris (n = 6). The mean diameter of FGL was 24.5±11.4 mm, and mean depth to the abdominal wall was 21.2±7.3 mm. While applying CEUS with high frequency transducer, specific diagnostic features, including arterial phase irregular intralesional vascularity (10/15, 66.7%), late phase hypoenhancement (12/15, 80%), destruction of gallbladder wall (8/15, 53.3%), infiltration to the adjacent liver (6/15, 40.0%) were significantly higher in malignant FGL. The overall sensitivity, specificity and diagnostic accuracy for the correct characterization of malignant FGL were significantly improved by CEUS with high frequency transducer (sensitivity 93.3%, specificity 88.5%, accuracy 100%). With its superior contrast resolution, CEUS performed with high frequency transducers is helpful to achieve better visualization of gallbladder fundus and make differential diagnosis of gallbladder lesions, which might greatly improve diagnostic confidence between malignant and benign FGL.

Tuning the polymer–graphene interfaces by picric acid molecules to improve the sensitivity of a prepared conductive polymer composite gas detector

A new structure of a polymer composite was designed to be used as a vapor sensor for detection of a set of volatile organic compounds (VOCs), namely ethanol, methanol, isopropyl alcohol (IPA), toluene and water as moisture in the atmosphere. Picric acid was used for physical decoration of graphene (Gr), as a conductive filler, and then, the modified graphene (Gr.PA) was added to polyvinyl alcohol (PVA) to design a conductive polymer composite (CPC) sensitive layer for detection of polar vapor analytes. The Fourier transfer infrared spectroscopy (FTIR) was used to study the physical adsorption of picric acid molecules on the surface of Gr. The experimental results revealed that the sensitivity of the prepared CPC transducer was dramatically improved through the decoration of Gr surfaces with PA molecules. The enhanced sensitivity was related to the addition of –OH and –NO2 functional groups on the surface of Gr (due to picric acid molecules). Those polar functional groups increased the diffusion driving force of polar analytes into the polymer composite. On the other hand, upon adding PA molecules, Gr–Gr junctions were tuned as sensitive sites, and the adsorbed vapor molecules increased the distance of Gr platelets, which, consequently, decreased the electron tunneling conductivity of the prepared CPC. The experimental results also proved that one could change the electrical conductivity of Gr as a p-type semiconductor through adsorption of analyte molecules on its surface. All in all, the attained results demonstrated that tuning the conductive filler junctions could be regarded as an exceptional strategy to improve the sensitivity of CPC transducers.

Piezoelectric and Inversely Piezoelectric Responses of Bone Tissue Plates in the Megahertz Range

Piezoelectricity in bone is thought to be a mechanism by which ultrasound promotes the healing of bone fractures. However, a few studies have been conducted in the more clinically relevant megahertz range. To understand the piezoelectricity in bone, we fabricated ultrasound transducers using bone samples as piezoelectric materials and identified the longitudinal ultrasound radiation and reception in the megahertz range. The maximum transmitting sensitivity of the bone transducer was 140 mPa/V, which was nearly 1/1000 of a polyvinylidene difluoride (PVDF) transducer that has better electrical properties and piezoelectricity. The resonance frequencies of the transducer depend on the plate thickness and angle between the bone axis (alignment direction of the hydroxyapatite crystallites) and ultrasound propagation direction, reflecting the anisotropic character of the bone. The reception and transmission sensitivities of the bone transducers also depend on the plate thickness and angle, showing maximum values at off-axis angles. These results indicate the existence of both piezoelectricity and inverse piezoelectricity in bone, which may be key factors in understanding the bone healing by low-intensity biophysical (electrical or mechanical) stimulation.

Estimation of Factors that Affect the Metrological Characteristics of Target Flow Meters

The article is devoted to the effective system crea­tion for recording liquids and gases flows. There is extremely relevant for creating metering units of fuel and energy resources.
 The aim of the work is to determine the influence of the flowed body geometric configuration of the sensitive element and its orientation relative to the direction of the flow on the hydrodynamic flow meter metrological characteristics, as well as determining the instruments’ rational location in the technological line
 Based on the example of the hydrodynamic class measuring transducers factors that have a significant impact on their metrological characteristics are determined, the degree of the transducers sensitivity to the measured medium flows asymmetry is revealed. The flows asymmetry is simulated by hydraulic resistan­ces of different spatial configurations (spatial elbow, elbow, double elbow, contraction, abrupt contraction). Simulation modeling of the operation of such devices is performed. Sensitive elements of different Gaussian curvatures such as zero (cylinder), positive (cone) and negative (hollow hemisphere) were studied.
 The value of the registration result uncertainty depends on the flow asymmetry and the instrument spatial orientation relative to the vertical axis in the technological network. The obtained results make it possible to clearly determine the instrument installation place in the technological network under conditions of maximum accuracy and minimal impact on the measured medium. This allows effectively using transducers in places of the technological network, taking into account the specific conditions for the metering units creation. There is no ne­cessary to make straight pipeline sections before and after the instruments.
 The researches results show that measuring instruments with flow bodies in the shape of a cone oriented the apex toward the flow are the best.

A numerical modeling strategy for passive electro-acoustic transducers

In this paper an alternative numerical/analytical method for determining the directivity-dependent receiving sensitivity of general electro-acoustic transducer is presented. Unfortunately, the computational effort of calculating the directivity-dependent receiving sensitivity is more expensive by orders of magnitude than determining the transmitting sensitivity. Using the underlying integral representation of the problem and the existence of resolvent kernels, a postprocessing approach is derived which enables simulations of the receiving sensitivity with the effort of calculating the transmitting sensitivities.