Piezoelectric Sensor Applications Research Articles

Analysis of Properties and Macroscopic Defects of Metallic Bars, Pipes, and Strands through the Spectrum of Low-Frequency Excitations.

It is demonstrated that the application of piezoelectric sensors to metallic bars and strands can enable determining the status of the integrity of these elements through the spectrum of their acoustic excitations. The voltage output of the piezo, secured to metal bars or strands, is fed to the input of a Fast Fourier Transform analyzer, which allows displaying the spectrum of the excitations from which information on the length, overall quality of the metal, and the presence of defects can be obtained. We show that the analysis, performed on several materials and strands of different lengths, could be useful for cases in which visible inspection and/or direct access to the entire body of the metallic elements is not possible. Applications of our study for testing metallic structures embedded in concrete foundations are reported for construction sites.

Fabrication and application of flexible piezoelectric sensor based on electrospun PVDF-TrFE nanofibers

Flexible piezoelectric sensors have recently demonstrated great promise for use in wearable electronics and electronic skin. In this study, electrospinning was used to generate piezoelectric PVDF-TrFE nanofiber sensors. The relationship between nanofiber alignment orientation and piezoelectric property was examined. The experimental results demonstrated that the piezoelectric property improved with the increasing of nanofiber alignment orientation. The response time of piezoelectric sensor was 2 ms, and the sensitivity was 0.446 V/N and 0.029 V/N at vibration frequency of 5 Hz and 1 Hz, respectively. In addition, the applications of flexible piezoelectric sensor in human joint movements and surface contact have been demonstrated, indicates the potential in the field of motion monitoring.

Hydrothermally grown pure and Er-doped ZnS nanocrystals based flexible piezoelectric nanogenerator for energy harvesting and sensing applications

Pure zinc sulphide (ZnS) and Er-doped ZnS nanocrystals were grown by hydrothermal method at low temperature. Powder XRD analysis reveals the formation of wurtzite hexagonal phase structure for both pure and Er-doped ZnS samples. Morphology of 2D nanocrystals for both pure and doped ZnS nanocrystals was confirmed by FESEM technique. Presence of Er element in Er-doped ZnS was confirmed by energy-dispersive X-ray spectroscopy. Further, both pure and Er-doped nanocrystals have been used as piezoelectric fillers in polydimethylsiloxane (PDMS) for the fabrication of flexible piezoelectric nanogenerators. The Er-doped ZnS based nanogenerator showed almost 9 times (∼ 36 V) higher open circuit voltage as compared to pure ZnS based nanogenerator (∼ 4 V). Then, Er-doped ZnS nanocrystals based device was used to harvest the mechanical energy under the human walking and running conditions. Also, this device generated significant electrical signal under the human elbow bending. The output performances of Er-doped ZnS based device indicates that it can be a potential candidate for mechanical energy harvesting under various human body motions as well as for wearable piezoelectric sensor applications.

Design and Construction of a Density-Controlled Traffic Light System

This work introduces the application of piezoelectric sensors on the road which intersects to form a T juncture, the application of the sensor aids in regulating the control of traffic density on each side of the road. Traffic congestion as of today is caused by the improper management of time and eventually leads to traffic delays. This was undoubtedly observed during early hours when a lot of civilians head out to their workstations and during closing hours in the evenings. The increasing population and economic activities in urban areas contribute to higher vehicle ownership and usage, leading to more traffic on the roads. It is achieved from the general desire of people to achieve goals, which ultimately leads to daily overcrowding of the present transportation infrastructure. But despite attempts at solutions, everyone despises traffic congestion, and it only gets unfavorable. The objective of this project is to create a dynamic road signal that is based on density. The synchronization signals automatically change to detect intersection traffic density. The components required to build this project include the microcontroller (Arduino uno), LEDs (light emitting diodes), piezoelectric sensors, jumper wires, a 9 V battery, a switch, and an operational amplifier. The result of the work focuses on the detection of density from a sensor which will be constructed underground to operate as a counter for every vehicle that passes by as it will be powered by a battery of approximately 9 V. The sensor which is known as the piezoelectric sensor abides by the rule of piezoelectric effect, which states that the stress produced from a non-static object, or the mechanical energy produced from a moving object will produce an electric charge in response to the mechanical energy generated. The electric charge produced from the piezoelectric sensor will be transmitted to the microcontroller (Arduino Uno). Through the input stage of the signal received, the program in the microcontroller will command the light-emitting diode (LEDs) to function accordingly to the state of density detected from each side of the road. Thereby regulating the flow of traffic movement efficiently and accurately. Overall, the application of the piezoelectric sensor on the road can accurately detect the presence of a vehicle passing.

High-Transconductance and Low-Leakage Current Single Aluminum Nitride Nanowire Field Effect Transistor

This study presents electrical transport properties of a catalyst-free grown single aluminum nitride nanowire field effect transistor (AlNNW-FET) exhibiting a very high transconductance of 26.9 pS, high on/off current ratio of 795.9, high conductivity of 9.8 x 10-4 Ω-1.cm-1, and a very low leakage current of 10 pA. The conductivity of AlN nanowire is two orders of magnitude higher than the reported studies. The AlNNW-FET reveals a dominant p-type conductivity. The p-type conductivity can be attributed to aluminum vacancies and complexes composed of Al vacancies and oxygen impurities. In consequence, the fabricated AlNNW-FET with high-performance, cost-effectiveness, and high-power efficiency is very well suited for use in low power and high temperature nanoelectronic and piezoelectric sensor applications, as well as integrated electro-optical devices including optomechanical devices and pyroelectric photodetectors.

The Role of Molecularly Imprinted Polymers In Sensor Technology: Electrochemical, Optical and Piezoelectric Sensor Applications

With the help of molecular imprinting technology, artificial receptors can be made and used for identification. This technique's limitless application increases polymer technology and makes it adaptable to other technologies. In this study, examples of sensor applications are used to explain molecular imprinting technology (MIT) and its brief history. MIT can be used to create polymer-based artificial receptors with remarkable selectivity and affinity to detect any target molecules that can be imprinted on a polymer. A monomer is synthesized around a template molecule to create a selective cavity that serves as an artificial receptor. Molecularly imprinted polymers (MIP) offer a wide range of uses and have recently garnered much attention. These polymers' production methods, production kinds, and molecular imprinting techniques are all thoroughly detailed. The outstanding properties of MIPs make a crucial contribution to sensor applications offering selective, fast, easy, and cost-effective analysis, which became very popular after Clark published his first biosensor study. Apart from the biological recognition receptors, MIPs have the advantage that they are not affected by physical conditions of the environment, such as temperature, pH, and ion strength. To overcome the biological recognition receptors' disadvantages, molecularly imprinted polymers can be used for sensor development. From the point of view of the review, the combination of MIPs and sensors was explained and proposed as an informative paper.

Application of micro-bolus injection and piezoelectric sensors to improve the safety of radiopharmaceuticals bolus injection

Radiopharmaceutical dynamic imaging typically necessitates intravenous injection via the bolus method. However, manual bolus injection carries the risk of handling errors as well as radiological injuries. Hence, there is potential for automated injection devices to replace manual injection methods. In this study, the effect of micro-bolus pulse injection technology was compared and verified by radioactive experiments using a programmable injection pump, and the overall bubble recognition experiment and rat tail vein simulation injection verification were performed using the piezoelectric sensor preloading method. The results showed that at the same injection peak speed, the effective flushing volume of micro-bolus pulse flushing (about 83 μL/pulse) was 49.65% lower than that of uniform injection and 25.77% lower than that of manual flushing. In order to avoid the dilution effect of long pipe on the volume of liquid, the use of piezoelectric sensor for sealing preloading detection could accurately predict the bubbles of more than 100 μL in the syringe. In the simulated injection experiment of rat tail vein, when the needle was placed in different tissues by preloading 100 μL normal saline, the piezoelectric sensor fed back a large difference in pressure attenuation rate within one second, which was 2.78% in muscle, 17.28% in subcutaneous and 54.71% in vein. Micro-bolus pulse injection method and piezoelectric sensor sealing preloading method have application potential in improving the safety of radiopharmaceutical automatic bolus injection.

Establishing a Relationship between the Piezoelectric Response and Oxygen Vacancies in Lead-Free Piezoelectrics.

BiFeO3-BaTiO3 (BF-BT)-based lead-free piezoceramics are desired materials for high-temperature applications of piezoelectric sensors with a high Curie temperature and good piezoelectric properties. Recent studies have shown that oxygen vacancies have a significant effect on electrostrain and piezoelectric properties. Interestingly, two different phenomena exist, i.e., the increase in piezoelectric properties is often associated with a decrease in the concentration of oxygen vacancies, while the increase in electrostrain is often associated with an increase in the concentration of oxygen vacancies. Especially, for BF-based ceramics, the physical mechanisms related to property differences caused by oxygen vacancies are rarely reported, which needs further exploration. Here, two ceramics with differences in their oxygen vacancy concentrations are designed. Based on Rayleigh analysis, thermal/electric field-induced domain response (ferroelectric scaling), and macro-microstructural characterization, we can conclude that the transient piezoelectric response and the aging process are significantly affected by the oxygen vacancy concentration. In other words, the increasing concentration of oxygen vacancies in BF-BT ceramics enhances the reversible piezoelectric response contributed by lattice distortion and strengthens the response of domain switching and domain wall motion to electric and thermal fields but deteriorates their aging behavior, which leads to the degradation of piezoelectric performance. Besides, polarization saturation and defect pegging significantly improve the temperature stability of the strain.

Development and Temperature Correction of Piezoelectric Ceramic Sensor for Traffic Weighing-In-Motion.

Weighing-In-Motion (WIM) technology is one of the main tools for pavement management. It can accurately describe the traffic situation on the road and minimize overload problems. WIM sensors are the core elements of the WIM system. The excellent basic performance of WIMs sensor and its ability to maintain a stable output under different temperature environments are critical to the entire process of WIM. In this study, a WIM sensor was developed, which adopted a PZT-5H piezoelectric ceramic and integrated a temperature probe into the sensor. The designed WIM sensor has the advantages of having a small size, simple structure, high sensitivity, and low cost. A sine loading test was designed to test the basic performance of the piezoelectric sensor by using amplitude scanning and frequency scanning. The test results indicated that the piezoelectric sensor exhibits a clear linear relationship between input load and output voltage under constant environmental temperature. The linear correlation coefficient R2 of the fitting line is up to 0.999, and the sensitivity is 4.04858 mV/N at a loading frequency of 2 Hz at room temperature. The sensor has good frequency-independent characteristics. However, the temperature has a significant impact on it. Therefore, the output performance of the piezoelectric ceramic sensor is stabilized under different temperature conditions by using a multivariate nonlinear fitting algorithm for temperature compensation. The fitting result R2 is 0.9686, the root mean square error (RMSE) is 0.2497, and temperature correction was achieved. This study has significant implications for the application of piezoelectric ceramic sensors in road WIM systems.

Enhancement of Piezoelectricity by Novel Poling Method of the Rare‐Earth Modified BiFeO3–BaTiO3 Lead‐Free Ceramics

AbstractIn piezoceramics, the Curie temperature (TC) and piezoelectric coefficient (d33) are often inversely proportional, so it is very difficult to optimize high piezoelectricity and TC simultaneously. In addition, the high and temperature‐insensitive piezoelectric strain coefficient (d33*) with small hysteresis is also a longstanding obstacle in the development of lead‐free ceramics. In this work, a facile approach of donor doping strategy is adopted to replace Ba2+ with Yb3+, Y3+, Sm3+, and Nd3+ as a result, a high TC of 450 °C and outstanding d33 of 422–436 pC N−1 is achieved by a novel magnetic poling method. Thermally‐stable and outstanding piezoelectric strain performance (d33* ≈ 520–550 pm V−1 and ΔST ≈ 10%) with small strain hysteresis (H < 20%) results are highly encourageable in lead‐free ceramics. The main factors contributing to high piezoelectricity are the morphotropic phase boundary, suppression of defect charges by donor doping, thermal quenching, mesoscale nanodomain size, and novel poling method. The excellent piezoelectric performance and high TC of this work are superior to those of state‐of‐the‐art piezoceramics. The synergistic approaches of compositional design strategy and novel poling process in this work are highly beneficial for temperature‐insensitive piezoelectric sensor and actuator applications.

Evaluation of the structure and electrical properties of (1−x)Bi0.5(Na0.80K0.20)0.5TiO3–xLiNbO3 ceramic composite for piezoelectric sensor applications

Lead-free piezoceramics ([Formula: see text])Bi[Formula: see text](Na[Formula: see text]K[Formula: see text]TiO3–xLiNbO3 (BNKT–LN) (where [Formula: see text], 0.025, 0.050 and 0.075[Formula: see text]mol fraction) were examined for their ferroelectric stability and subsequent modifications. Traditional solid-state reaction techniques were used to create the BNKT–LN piezoceramics, which were then sintered at a temperature of 1200°C. We concentrated on the structural, dielectric, piezoelectric and ferroelectric properties of the BNKT–LN ceramics. The powder X-ray diffraction pattern revealed a single perovskite structure with no secondary phases, as was observed. The temperature-dependent dielectric curves demonstrated that the maximum dielectric constant ([Formula: see text]) is present in the pure BNKT sample and diffuses to a low value when the LN concentration rises. SEM confirms the material’s surface shape, and decreasing grain sizes are seen as the LN content rises. The BNKT–LN ceramics’ P–E hysteresis loops demonstrate good ferroelectric characteristics, with a maximum at 20 kV/cm. With an increase in LN concentration, remnant polarization ([Formula: see text]) and coercive field ([Formula: see text]) show a trend of increasing, reducing and then increasing. The maximum value of the piezoelectric coefficient ([Formula: see text]) for the combined samples was 147[Formula: see text]pC/N. As a result, the lead-free ceramic BNKT (BNKT–LN) doped with LN is an auspicious choice for piezoelectric sensor applications.

Piezoelectric Materials and Sensors for Structural Health Monitoring: Fundamental Aspects, Current Status, and Future Perspectives

Structural health monitoring technology can assess the status and integrity of structures in real time by advanced sensors, evaluate the remaining life of structure, and make the maintenance decisions on the structures. Piezoelectric materials, which can yield electrical output in response to mechanical strain/stress, are at the heart of structural health monitoring. Here, we present an overview of the recent progress in piezoelectric materials and sensors for structural health monitoring. The article commences with a brief introduction of the fundamental physical science of piezoelectric effect. Emphases are placed on the piezoelectric materials engineered by various strategies and the applications of piezoelectric sensors for structural health monitoring. Finally, challenges along with opportunities for future research and development of high-performance piezoelectric materials and sensors for structural health monitoring are highlighted.

PS-BPC02-7: RADIAL-DIGITAL PULSE WAVE VELOCITY: STIFFNESS OF SMALL CONDUIT ARTERIES INCREASES AFTER NITROGLYCERIN ADMINISTRATION

Objective: The alteration of the physiological stiffness gradient within larger vessels would increase the transmission of greater pulsatility to the microcirculation, thus explaining the damage to the pressure-sensitive organs. We aimed to describe the response of small conduit arteries of the hand (radial-digital PWV, rd-PWV) following the pharmacological alteration of the stiffness gradient using nitroglycerin. Design and method: Simultaneous application of piezoelectric sensors (Complior) at the level of the carotid (c), the radial artery (r) and the tip of the index finger (d) was used to calculate the rd-PWV by the following formula (rd-PWV = cd-cr direct distances/cd-cr transit times). Rd-PWV was obtained before and 4 minutes after a sublingual administration of 0.4 mg of NTG, in healthy adults (controls, n = 36) and patients with moderate chronic kidney disease (CKD, n = 30). Changes in arterial stiffness pre-post NTG and comparisons between the two groups were analyzed respectively with paired or independent samples t-tests. Results: Compared to controls, the CKD group was older (69 ± 15 years vs. 41 ± 20 years) and more hypertensive. Despite similar cd-PWV and cr-PWV, rd-PWV was significantly lower in CKD than in controls (3.6 ± 1.4 m/s vs. 4.5 ± 1.8 m/s, p = 0.024), but this difference faded (p = 0.145) after adjustment for age. Post NTG, brachial blood pressure decreased and heart rate increased similarly between groups (see Table 1). Cr-PWV decreased after NTG (both groups p < 0.001) while rd-PWV increased in controls (from 4.62 ± 1.49 m/s to 5.94 ± 2.29 m/s, p < 0.001) and in CKD (from 3.71 ± 1.60 m/s to 5.18 ± 2.12 m/s, p < 0.001), in a similar extent (p = 0.111 for interaction term). Cd-PWV significantly increased post-NTG only in the CKD group (p = 0.009). Conclusions: Again, we observed opposing changes in the regional stiffnesses of two distinct vascular territories following the administration of a vasodilator. Here, the two segments were mid-size and small conduit muscular arteries. This technique, adapted by our team for short peripheral arterial segments, may broaden our understanding of the consequences of the inversion of the stiffness gradient.

Enantiomeric hybrid high-temperature multiaxial ferroelectrics with a narrow bandgap and high piezoelectricity

Ferroelectric semiconductors have sparked growing attention in the field of optoelectronics, due to their unique ferroelectric photovoltaic effect. Recently, substantial efforts have been devoted to the development of ferroelectric semiconductors, including inorganic oxides, organic-inorganic hybrids, and metal-free perovskites. Nevertheless, reports of ferroelectric semiconductors with a bandgap of less than 2 eV have been scarce. Here, in combination with the incorporation of triiodide (I3−) and the introduction of chiral cations, we successfully constructed a pair of enantiomeric organic-inorganic hybrid ferroelectric semiconductors, (S-1,2-DAP·I)4·I3·BiI6 and (R-1,2-DAP·I)4·I3·BiI6 (R/S-1,2-DAP = (R/S)-(–)-1,2-diaminopropane), which possess high-temperature multiaxial ferroelectric phase transition with an Aizu notation of 422F2(s) at 405 K, a narrow bandgap of 1.56 eV comparable to that of CH3NH3PbI3 (∼1.5 eV), and an impressive piezoelectric response (piezoelectric coefficient, d22 of 35 pC/N) on par with PVDF (polyvinylidene fluoride, 30 pC/N). With intriguing attributes, (S-1,2-DAP·I)4·I3·BiI6 and (R-1,2-DAP·I)4·I3·BiI6 exhibit great potential for application of self-power polarized-light detection and piezoelectric sensors.

High temperature piezoelectric accelerometer fabricated by 0.75BiFeO3–0.25BaTiO3 ceramics with operating temperature over 450 °C

Owing to the high Curie temperature and good piezoelectric thermal stability, BiFeO3–BaTiO3 ceramics show great potentials for high-temperature piezoelectric sensor applications. In this paper, a compression-mode piezoelectric sensor was fabricated by the lead-free and high-temperature 0.75BiFeO3–0.25BaTiO3–MnO2 (BFBT25–Mn) ceramic and its sensitivity was characterized from room temperature to 550 °C over a frequency range of 200–1000 Hz. The output charge of the BFBT25–Mn piezoelectric sensor is independent of the measuring frequency at different temperatures. The maximum working temperature of the BFBT25–Mn piezoelectric sensor is 450 °C, about 250, 150, and 100 °C higher than those of these piezoelectric sensors fabricated by PZT-5A, BSPT64–Mn, and BSPT66–Mn ceramics, respectively. The temperature sensitivity coefficient from room temperature to 350 °C of the BFBT25–Mn piezoelectric sensor is 30% of that for the BSPT66–Mn sensor. Furthermore, the sensitivity of the BFBT25–Mn piezoelectric sensor is stable with the dwelling time at 400 °C. These results indicate that the BFBT25–Mn ceramic is a strong competitor for high temperature sensing applications.

Characterization of Piezoelectric Energy Production from Asphalt Pavements Using a Numerical-Experimental Framework

The recent increase in demand for electric energy and different ways of harvesting and generating it has been a key research stream in transportation infrastructure in Brazil. Since pavement structures are subjected to the mechanical load of millions of vehicles, the application of piezoelectric sensors is adequate, transforming deformations and vibrations on its layers into electric power. The general objective of this study was to investigate the use of piezoelectricity as a source of renewable energy applied to roadways using computational simulations and laboratory tests. The results indicate that factors such as frequency, load, the number of piezo cells, and spacing all affect the amount of power harvested. Regarding power generation in the simulation and laboratory characterization, the highest values obtained were 648.8 mW and 226.9 mW, respectively. The analysis indicates there is a correlation between the laboratory tests and the computational simulations, enabling the prototype application to capture up to 76.56 MWh of energy per month. Usage of piezoelectricity has been demonstrated to be a promising alternative to complement the Brazilian energy matrix and reduce the environmental impact.

Textured CaBi4Ti4O15 ceramics with large piezoelectricity, excellent thermal stability and high resistivity

The bismuth layer-structured ferroelectrics (BLSF) are promising high-temperature piezoelectric materials, in which large piezoelectricity, good thermal stability and high electrical resistivity are desired. Here highly textured CaBi4Ti4O15 BLSF ceramics with orientation factor of 82% have been fabricated by spark plasma sintering technique. The piezoelectric coefficient d33 is significantly enhanced by 250%, from 7.2 pC/N for the texture-less sample to 25.3 pC/N for the textured one, accompanied by a high Curie temperature TC= 788 °C. The variation of d33 is below 5% in the temperature range of 25–500 °C, showing excellent thermal stability. The textured sample exhibits high electrical resistivity ρ = 2.1 × 1011 Ω·cm, an order of magnitude larger than that of the texture-less sample. At the temperature as high as 500 °C, the textured sample still maintains excellent electrical properties of d33 = 24.2 pC/N, tanδ = 9.9% and ρ = 2.7 × 106 Ω·cm, suggesting that the textured CaBi4Ti4O15 ceramics could be a potential candidate for high-temperature piezoelectric sensor or detector applications.

Flexible, Equipment-Wearable Piezoelectric Sensor With Piezoelectricity Calibration Enabled by In-Situ Temperature Self-Sensing

Flexible piezoelectric sensors have attracted much attention due to good dynamic response, high sensitivity, and self-powered sensing advantages. However, piezoelectric outputs are usually affected by temperature variation, thus limit their applications on industrial intelligent equipment. Here, a new flexible piezoelectric sensor with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> temperature sensing and piezoelectricity calibration function is developed. The sensor can calibrate the piezoelectric output based on temperature to achieve high-accuracy sensing capability. It consists of a flexible polyimide substrate, S-shaped platinum interdigital electrodes and aligned piezoelectric fibers. The designed S-type electrode with thermosensitive effect measures the temperature <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> , and then the piezoelectric strain output from P(VDF-TrFE) fibers is calibrated according to the temperature. The temperature sensor has a high sensitivity of 19.2 Ω/°C with good linearity, and keeps good accuracy under bending deformation. When the working temperature range is 25 °C–60 °C, the sensor has a good piezoelectricity calibration effect, so that it maintains a stable sensitivity of 244 mV/μϵ without being affected by temperature. Furthermore, this article systematically studied the influence of temperature on piezoelectric output, and established a calibration method to improve the accuracy of piezoelectric output under temperature changes. Finally, the flexible integrated sensor was conformally attached on the bearing surface to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> sensing temperature and micro-strain. The structural design and piezoelectricity calibration method can promote the application of flexible piezoelectric sensors in the industrial field.

RADIAL-DIGITAL PULSE WAVE VELOCITY: RESPONSE OF SMALL ARTERIES TO A MODIFICATION OF ARTERIAL STIFFNESS GRADIENT INDUCED BY NITROGLYCERIN

Objective: We previously demonstrated that it is possible to modulate the arterial stiffness gradient with the administration of nitroglycerin (NTG). This alteration of the physiological stiffness gradient would increase the transmission of greater pulsatility to the microcirculation, thus explaining the damage to the pressure-sensitive organs. We aimed to describe small conducting arteries response following the pharmacological alteration of the stiffness gradient using regional stiffness of the hand (radial-digital PWV, rd-PWV). Design and method: The simultaneous application of piezoelectric sensors (Complior) at the level of the carotid ®, the radial artery ®, and the tip of the index finger (d) was used to calculate the rd-PWV by the following formula (rd-PWV = cd-cr distances/cd-cr transit time). Rd-PWV was obtained before and 4 minutes after a sublingual administration of 0.4 mg of NTG, in healthy adults (controls, n = 23) and patients with moderate chronic kidney disease (CKD, n = 18). Changes in arterial stiffness pre-post NTG and comparisons between the two groups were analyzed using generalized estimating equations. Results: Pre NTG, despite similar cr-PWV, rd-PWV in CKD seemed lower than controls (3.7 ± 1.6 m/s vs. 4.6 ± 1.5 m/s, p = 0.067). This difference between the two groups faded (p = 0.865) after adjusting for age, where the standardized coefficient B of age = -0.407 (p = 0.037). Post NTG, cr-PWV decreased in both groups (p &lt; 0.001) while rd-PWV increased similarly (no interaction, p = 0.111)), between controls (from 4.62 ± 1.49 m/s to 5.94 ± 2.29m /s, p &lt; 0.001) and CKD (from 3.71 ± 1.60 m/s to 5.18 ± 2.12m/s, p &lt; 0.001). There was no difference in changes of brachial pressures between the two groups. Conclusions: Again, we observed opposite changes in arterial stiffness in two different arterial territories following the administration of NTG. In contrast with cr-PWV, regional stiffness of the hand increase after NTG administration. Rd-PWV is a new approach for the measurement of the regional stiffness of small arteries that could open the way to a better hemodynamic understanding of the consequences of the inversion of the stiffness gradient.

Tailoring the chemical heterogeneity of Mn-modified 0.75BiFeO3-0.25BaTiO3 ceramics for piezoelectric sensor applications

The Mn-modified 0.75BiFeO3-0.25BaTiO3 (75BFBTMn) piezoelectric ceramic possesses a high depolarization temperature of 500 °C and a large piezoelectric coefficient of 110 pC/N, showing the potential for high temperature piezoelectric sensors. However, 75BFBTMn ceramic usually suffers dielectric degradation and abrupt drop of piezoelectric coefficient in the range of 300 °C to 500 °C. Combined the high-energy synchrotron X-ray diffraction analysis with Backscatter-SEM results, it is demonstrated that the electrical thermal instability is owing to the existence of chemical inhomogeneity. The Air-annealing treatment is able to decrease the volume fraction of pseudo-cubic phase and the lattice distortion, removes the chemical inhomogeneity in the grain and free Bi2O3 at grain boundary, and then eliminates dielectric anomalies and piezoelectric degradation with temperature. These results indicate that air-annealing is a simple but effective method to eliminate the chemical inhomogeneity in 75BFBTMn ceramics, thereby improving the property thermal stability for high temperature piezoelectric sensor applications.