Showing papers on "Piezoelectric sensor published in 2017"

Self-Powered Real-Time Arterial Pulse Monitoring Using Ultrathin Epidermal Piezoelectric Sensors

Abstract: Continuous monitoring of an arterial pulse using a pressure sensor attached on the epidermis is an important technology for detecting the early onset of cardiovascular disease and assessing personal health status. Conventional pulse sensors have the capability of detecting human biosignals, but have significant drawbacks of power consumption issues that limit sustainable operation of wearable medical devices. Here, a self-powered piezoelectric pulse sensor is demonstrated to enable in vivo measurement of radial/carotid pulse signals in near-surface arteries. The inorganic piezoelectric sensor on an ultrathin plastic achieves conformal contact with the complex texture of the rugged skin, which allows to respond to the tiny pulse changes arising on the surface of epidermis. Experimental studies provide characteristics of the sensor with a sensitivity (≈0.018 kPa-1 ), response time (≈60 ms), and good mechanical stability. Wireless transmission of detected arterial pressure signals to a smart phone demonstrates the possibility of self-powered and real-time pulse monitoring system.

Integrated 3D printing and corona poling process of PVDF piezoelectric films for pressure sensor application

Abstract: This paper presents a novel process to fabricate piezoelectric films from polyvinylidene fluoride (PVDF) polymer using integrated fused deposition modeling (FDM) 3D printing and corona poling technique Corona poling is one of many effective poling processes that has received attention to activate PVDF as a piezoelectric responsive material The corona poling process occurs when a PVDF polymer is exposed to a high electric field created and controlled through an electrically charged needle and a grid electrode under heating environment FDM 3D printing has seen extensive progress in fabricating thermoplastic materials and structures, including PVDF However, post processing techniques such as poling is needed to align the dipoles in order to gain piezoelectric properties To further simplify the piezoelectric sensors and structures fabrication process, this paper proposes an integrated 3D printing process with corona poling to fabricate piezoelectric PVDF sensors without post poling process This proposed process, named 'Integrated 3D Printing and Corona poling process' (IPC), uses the 3D printer's nozzle and heating bed as anode and cathode, respectively, to create poling electric fields in a controlled heating environment The nozzle travels along the programmed path with fixed distance between nozzle tip and sample's top surface Simultaneously, the electric field between the nozzle and bottom heating pad promotes the alignment of dipole moment of PVDF molecular chains The crystalline phase transformation and output current generated by printed samples under different electric fields in this process were characterized by a Fourier transform infrared spectroscopy and through fatigue load frame It is demonstrated that piezoelectric PVDF films with enhanced β-phase percentage can be fabricated using the IPC process In addition, mechanical properties of printed PVDF was investigated by tensile testing It is expected to expand the use of additive manufacturing to fabricate piezoelectric PVDF-based devices for applications such as sensing and energy harvesting

Flexible Piezoelectric Touch Sensor by Alignment of Lead-Free Alkaline Niobate Microcubes in PDMS

Abstract: A highly sensitive, lead-free, and flexible piezoelectric touch sensor is reported based on composite films of alkaline niobate K0.485Na0.485Li0.03NbO3 (KNLN) powders aligned in a polydimethylsiloxane (PDMS) matrix. KNLN powder is fabricated by solid-state sintering and consists of microcubes. The particles are dispersed in uncured PDMS and oriented by application of an oscillating dielectrophoretic alignment field. The dielectric constant of the composite film is almost independent of the microstructure, while upon alignment the piezoelectric charge coefficient increases more than tenfold up to 17 pC N−1. A quantitative analysis shows that the origin is a reduction of the interparticle distance to under 1.0 μm in the aligned bicontinuous KNLN chains. The temperature stable piezoelectric voltage coefficient exhibits a maximum value of 220 mV m N−1, at a volume fraction of only 10%. This state-of-the-art value outperforms bulk piezoelectric ceramics and composites with randomly dispersed particles, and is comparable to the values reported for the piezoelectric polymers polyvinylidenefluoride and its random copolymer with trifluoroethylene. Optimized composite films are incorporated in flexible piezoelectric touch sensors. The high sensitivity is analyzed and discussed. As the fabrication technology is straightforward and easy to implement, applications are foreseen in flexible electronics such as wireless sensor networks and biodiagnostics.

A Low-Power Wireless Piezoelectric Sensor-Based Respiration Monitoring System Realized in CMOS Process

Abstract: This paper presents a methodology of monitoring respiration pattern using piezoelectric transducer incorporating CMOS integrated circuits for signal processing and data transmission. As a proof of concept, the system has been tested by placing electrodes on human chest using adhesive hydrogel to detect the pulsatile vibration due to respiration. The system can be used either as a wearable device itself or alternatively can be attached to a jacket or a chest belt. The front-end transducer is a piezoelectric material-based sensor, which is comprised of a ferroelectric polymer named polyvinylidene-fluoride (PVDF). PVDF is also biocompatible, which makes the sensor suitable to be used as a wearable device. The charge produced by the sensor is converted to a proportional voltage signal with the help of a charge amplifier designed in a standard 130-nm CMOS process with eight metal and one poly layer. The analog voltage signal acquired from the charge amplifier is then converted into a digital signal using a reconfigurable pipelined analog-to-digital converter for ease of transmission. An impulse-radio ultra-wideband transmitter operating in the frequency range of 3.1–5 GHz is designed for wireless transmission of the data. The smaller footprint, lighter weight, wireless telemetry, and low-cost material along with the low-power integrated CMOS circuitry for signal processing and data transmission make the proposed system an attractive choice for stable respiration monitoring system.

Distributed Piezoelectric Sensor System for Damage Identification in Structures Subjected to Temperature Changes.

Abstract: Structural health monitoring (SHM) is a very important area in a wide spectrum of fields and engineering applications. With an SHM system, it is possible to reduce the number of non-necessary inspection tasks, the associated risk and the maintenance cost in a wide range of structures during their lifetime. One of the problems in the detection and classification of damage are the constant changes in the operational and environmental conditions. Small changes of these conditions can be considered by the SHM system as damage even though the structure is healthy. Several applications for monitoring of structures have been developed and reported in the literature, and some of them include temperature compensation techniques. In real applications, however, digital processing technologies have proven their value by: (i) offering a very interesting way to acquire information from the structures under test; (ii) applying methodologies to provide a robust analysis; and (iii) performing a damage identification with a practical useful accuracy. This work shows the implementation of an SHM system based on the use of piezoelectric (PZT) sensors for inspecting a structure subjected to temperature changes. The methodology includes the use of multivariate analysis, sensor data fusion and machine learning approaches. The methodology is tested and evaluated with aluminum and composite structures that are subjected to temperature variations. Results show that damage can be detected and classified in all of the cases in spite of the temperature changes.

Early Damage Detection in Composites during Fabrication and Mechanical Testing

Abstract: Fully integrated monitoring systems have shown promise in improving confidence in composite materials while reducing lifecycle costs. A distributed optical fibre sensor is embedded in a fibre reinforced composite laminate, to give three sensing regions at different levels through-the-thickness of the plate. This study follows the resin infusion process during fabrication of the composite, monitoring the development of strain in-situ and in real time, and to gain better understanding of the resin rheology during curing. Piezoelectric wafer active sensors and electrical strain gauges are bonded to the plate after fabrication. This is followed by progressive loading/unloading cycles of mechanical four point bending. The strain values obtained from the optical fibre are in good agreement with strain data collected by surface mounted strain gauges, while the sensing regions clearly indicate the development of compressive, neutral, and tensile strain. Acoustic emission event detection suggests the formation of matrix (resin) cracks, with measured damage event amplitudes in agreement with values reported in published literature on the subject. The Felicity ratio for each subsequent loading cycle is calculated to track the progression of damage in the material. The methodology developed here can be used to follow the full life cycle of a composite structure, from manufacture to end-of-life.

Electromechanical Fields in Piezoelectric Semiconductor Nanofibers under an Axial Force

Abstract: Piezoelectric semiconductors (PS) nanofibers, which simultaneously exhibit piezoelectricity and unique electric conductive behavior, have huge applications in sensors, energy harvesters, and piezoelectric field effect transistors. Electromechanical fields and charge carrier in PS nanofibers can be effectively controlled by a mechanical force. One-dimensional linear equations for PS nanofibers, which are suitable for small axial force and small electron concentration perturbation, are presented. Analytical expressions for the electromechanical fields and electron concentration in the fiber are obtained. Numerical results show that the electromechanical fields near the two ends are sensitive to the initial electron concentration and the applied axial force.

Human–computer interface glove using flexible piezoelectric sensors

Abstract: In this note, we propose a human–computer interface glove based on flexible piezoelectric sensors. We select polyvinylidene fluoride as the piezoelectric material for the sensors because of advantages such as a steady piezoelectric characteristic and good flexibility. The sensors are installed in a fabric glove by means of pockets and Velcro bands. We detect changes in the angles of the finger joints from the outputs of the sensors, and use them for controlling a virtual hand that is utilized in virtual object manipulation. To assess the sensing ability of the piezoelectric sensors, we compare the processed angles from the sensor outputs with the real angles from a camera recoding. With good agreement between the processed and real angles, we successfully demonstrate the user interaction system with the virtual hand and interface glove based on the flexible piezoelectric sensors, for four hand motions: fist clenching, pinching, touching, and grasping.

On-Line Corrosion Monitoring of Plate Structures Based on Guided Wave Tomography Using Piezoelectric Sensors

Abstract: Corrosion is a major safety and economic concern to various industries. In this paper, a novel ultrasonic guided wave tomography (GWT) system based on self-designed piezoelectric sensors is presented for on-line corrosion monitoring of large plate-like structures. Accurate thickness reconstruction of corrosion damages is achieved by using the dispersive regimes of selected guided waves and a reconstruction algorithm based on full waveform inversion (FWI). The system makes use of an array of miniaturised piezoelectric transducers that are capable of exciting and receiving highly dispersive A0 Lamb wave mode at low frequencies. The scattering from transducer array has been found to have a small effect on the thickness reconstruction. The efficiency and the accuracy of the new system have been demonstrated through continuous forced corrosion experiments. The FWI reconstructed thicknesses show good agreement with analytical predictions obtained by Faraday's law and laser measurements, and more importantly, the thickness images closely resemble the actual corrosion sites.

A wearable piezoelectric bending motion sensor for simultaneous detection of bending curvature and speed

Abstract: For simultaneous detection of bending curvature and speed, a wearable bending motion sensor was developed by measuring the output voltage signals. A discrepancy in the piezoelectric output voltages was effectively sensed as a function of bending curvature and speed for recognition of bending motions of the piezoelectric element. This simultaneously bending curvature and speed detectable flexible bending motion sensor is superior compared to other piezoelectric sensors which demonstrated a difference in piezoelectric output signals as a function of only bending curvature. For the wearable platform of the device, elastic ZnO NR–PDMS and Ag NW–SWCNT were utilized as active and electrode materials. This wearable and flexible piezoelectric bending motion sensor is expected to be applied toward the realization of artificial skin motion detectors.

Facile Fabrication of a Flexible LiNbO3 Piezoelectric Sensor through Hot Pressing for Biomechanical Monitoring.

Abstract: Wearable pressure sensors have attracted increasing attention for biomechanical monitoring due to their portability and flexibility. Although great advances have been made, there are no facile methods to produce sensors with good performance. Here, we present a simple method for manufacturing flexible and self-powered piezoelectric sensors based on LiNbO3 (LN) particles. The LN particles are dispersed in polypropylene (PP) doped with multiwalled carbon nanotubes (MWCNTs) by hot pressing (200 °C) to form a flexible LN/MWCNT/PP piezoelectric composite film (PCF) sensor. This cost-effective sensor has high sensitivity (8 Pa), fast response time (ca. 40 ms), and long-term stability (>3000 cycles). Measurements of pressure changes from peripheral arteries demonstrate the applicability of the LN/MWCNT/PP PCF sensor to biomechanical monitoring as well as its potential for biomechanics-related clinical diagnosis and forecasting.

Investigation on the factors influencing the performance of piezoelectric energy harvester

Abstract: In this study, we devised a promising method to harvest the clean power from vehicle vibrations. We tested the electrical response of stacked piezoelectric units at different temperatures and loadings by using indoor laboratory tests. It is also discovered that ambient temperature has a great influence on the piezoelectric power generation. The generated electric energy of piezoelectric unit increased with increase in the loading and their relationship follow the cubic polynomial. It is demonstrated that there is a linear correlation between the open-circuit voltage and the amount of charge generated of the piezoelectric unit. The output energy increases with an increase in the frequency and the load.

Auxetic behavior and acoustic properties of microstructured piezoelectric strain sensors

Abstract: The use of multifunctional composite materials adopting piezo-electric periodic cellular lattice structures with auxetic elastic behavior is a recent and promising solution in the design of piezoelectric sensors. In the present work, periodic anti-tetrachiral auxetic lattice structures, characterized by different geometries, are taken into account and the mechanical and piezoelectrical response are investigated. The equivalent piezoelectric properties are obtained adopting a first order computational homogenization approach, generalized to the case of electro-mechanical coupling, and various polarization directions are adopted. Two examples of in-plane and out-of-plane strain sensors are proposed as design concepts. Moreover, a piezo-elasto-dynamic dispersion analysis adopting the Floquet–Bloch decomposition is performed. The acoustic behavior of the periodic piezoelectric material with auxetic topology is studied and possible band gaps are detected.

On-Chip Feedthrough Cancellation Methods for Microfabricated AFM Cantilevers With Integrated Piezoelectric Transducers

Abstract: Active microcantilevers with on-chip sensing and actuation capabilities provide significant advantages in tapping-mode atomic force microscopy. The collocated transduction in active cantilevers enables effective control of their dynamics, allowing for the modification of the quality ( $Q$ ) factor and operation at higher flexural modes to obtain higher scan rates. However, having closely spaced transducers in dynamic applications often results in electrical crosstalk from the actuation signal to the sensor output. As a result, the dynamic response of the cantilever becomes heavily dominated by this feedthrough, making the use of on-chip transduction impractical for atomic force microscope (AFM) imaging without cancelling this undesired effect. In this paper, we propose two on-chip feedthrough cancellation methods based on pseudo-differential actuation and differential sensing concepts. The implementation of the methods is demonstrated by the use of two microfabricated cantilevers with separate piezoelectric sensors and actuators. Following the cancellation of the feedthrough, both cantilevers are successfully employed for AFM imaging using the on-chip transducers for actuation and deflection sensing. [2017-0101]

Diagnosis and validation of damaged piezoelectric sensor in electromechanical impedance technique

Abstract: Piezoelectric sensor diagnosis and validity assessment as a prior component of structural health monitoring system are necessary in the practical application of electromechanical impedance technique. This article proposed an innovative sensor self-diagnosis process based on extracting the characterization of the real admittance (inverse of impedance) signature within a high-frequency range, which covered both diagnosis on damaged sensor after its installation and discrimination of sensor and structural damages during structural health monitoring process. Theoretical analysis was derived from the impedance model of piezoelectric-bonding layer-structure dynamic interaction system. Experimental investigations on piezoelectric sensor-bonded steel beam involved with structural damages of mass addition and notch damage were conducted to verify the process. It was found that the real admittance was reliable and critical in sensor diagnosis, and sensor faults of debonding, scratch, and breakage can be identified ...

Refined zigzag theory for vibration analysis of viscoelastic functionally graded carbon nanotube reinforced composite microplates integrated with piezoelectric layers

Abstract: Damped free vibration of carbon nanotube reinforced composite microplate bounded with piezoelectric sensor and actuator layers are investigated in this study. For the mathematical modeling of sandw...

A High Performance Piezoelectric Sensor for Dynamic Force Monitoring of Landslide

Abstract: Due to the increasing influence of human engineering activities, it is important to monitor the transient disturbance during the evolution process of landslide. For this purpose, a high-performance piezoelectric sensor is presented in this paper. To adapt the high static and dynamic stress environment in slope engineering, two key techniques, namely, the self-structure pressure distribution method (SSPDM) and the capacitive circuit voltage distribution method (CCVDM) are employed in the design of the sensor. The SSPDM can greatly improve the compressive capacity and the CCVDM can quantitatively decrease the high direct response voltage. Then, the calibration experiments are conducted via the independently invented static and transient mechanism since the conventional testing machines cannot match the calibration requirements. The sensitivity coefficient is obtained and the results reveal that the sensor has the characteristics of high compressive capacity, stable sensitivities under different static preload levels and wide-range dynamic measuring linearity. Finally, to reduce the measuring error caused by charge leakage of the piezoelectric element, a low-frequency correction method is proposed and experimental verified. Therefore, with the satisfactory static and dynamic properties and the improving low-frequency measuring reliability, the sensor can complement dynamic monitoring capability of the existing landslide monitoring and forecasting system.

Zero-power sensors with near-zero-power wakeup switches for reliable sensor platforms

Abstract: The near zero-power sensor node solution is presented with piezoelectric sensors and DC tunable threshold electrostatic switches. A sensor suite measuring acceleration, rotation, and magnetic field based on PZT lateral bimorphs is used with NEMS switches for the detection of a desired signal pattern and generating a wake up trigger. The sensors are capable of detecting physical signals from 5 Hz to 1.5 kHz, with sourcing load capacitances as high as 200 pF. The sensor sensitivities achieved are: 0.1 V/g for the accelerometer, 31 mV/Gauss for the magnetic field, and 0.31 mV/(°/s) for rotation. NEMS switches, with threshold voltages in the mV to 15V range, can combine multiple sensor outputs through multi-gate actuation to detect desired event specific features. Using the sensors, we demonstrate the detection of a portable electrical generator in its different operational modes (On/Off state and the Eco mode).