Piezoelectric Polymer Sensors Research Articles

A vital signsignal noise suppression method for wearable piezoelectric devices.

This paper tackles the problem of noise suppression during vital signsignal monitoring. Physiological signal monitoring is a significant and promising medical monitoring method, and wearable medical monitoring devices based on piezoelectric polymer sensors are a trending way for their advantages of being flexible in the shape, portable to use, and comfortable to wear. However, this raises the question that the measured signal contains much more noise components. To avoid the following shortcoming of low signal to noise ratio (SNR), a noise suppression method based on improved wavelet threshold and empirical mode decomposition combined with singular value decomposition (SVD) screening the intrinsic mode function (IMF) components is proposed. A wavelet transform is first used under the combination of hard and soft thresholds to focus the target range in the low-frequency region where the energy of the physiological signal is concentrated. Then, a complete ensemble empirical mode decomposition is used to decompose the signal effectively, which can resist the influence of random noises. Meanwhile, a SVD decomposition procedure was used to filter out the lower correlated IMF components to retain the validity of the original signal. We verified the effectiveness of the proposed method through simulated and measured experiments as well as the advantages and disadvantages of the algorithm compared with other physiological signal denoising algorithms through SNR filtering results, power spectrum distribution, and other perspectives. The results proved that the proposed method could effectively remove more detailed noise and improve the SNR of the signal efficiently, which is more conducive to the demand for auxiliary medical diagnosis in the future.

Electrospun Core–Sheath PVDF Piezoelectric Fiber for Sensing Application

In recent years, piezoelectric polymer sensors are used in energy harvesting and self-powered sensing due to their flexibility, low density, and high piezoelectric constant, and their performances may be improved through a careful architectural design. Herein, we reported a facile strategy for fabricating core-sheath piezoelectric fiber (C-PEF) by directly electrospinning poly(vinylidene fluoride) (PVDF) onto the stainless steel wires. Such C-PEF can well respond to bending deformation with different degrees, and therefore it can be assembled into a piezoelectric bending sensor for airflow speed sensing. Furthermore, spring-like structured C-PEF (S-C-PEF) can serve as a piezoelectric spring sensor and in a sophisticated manner monitor human sleep behavior. This work paves a way for developing multigeometric piezoelectric sensors though a low-cost, facile, and reliable method, showing potential applications including bending sensing and health monitoring.

Validation of Screen-Printed Electronic Skin Based on Piezoelectric Polymer Sensors.

This paper proposes a validation method of the fabrication technology of a screen-printed electronic skin based on polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE) piezoelectric polymer sensors. This required researchers to insure, through non-direct sensor characterization, that printed sensors were working as expected. For that, we adapted an existing model to non-destructively extract sensor behavior in pure compression (i.e., the d33 piezocoefficient) by indentation tests over the skin surface. Different skin patches, designed to sensorize a glove and a prosthetic hand (11 skin patches, 104 sensors), have been tested. Reproducibility of the sensor response and its dependence upon sensor position on the fabrication substrate were examined, highlighting the drawbacks of employing large A3-sized substrates. The average value of d33 for all sensors was measured at incremental preloads (1–3 N). A systematic decrease has been checked for patches located at positions not affected by substrate shrinkage. In turn, sensor reproducibility and d33 adherence to literature values validated the e-skin fabrication technology. To extend the predictable behavior to all skin patches and thus increase the number of working sensors, the size of the fabrication substrate is to be decreased in future skin fabrication. The tests also demonstrated the efficiency of the proposed method to characterize embedded sensors which are no more accessible for direct validation.

A new device for real-time peroperative monitoring of ossicular chain reconstruction during middle ear surgery.

To limit functional surgical failure and reduce the rate of revision surgery in case of surgical ossicular chain reconstruction, a piezoelectric device was developed for assessment of ossicular chain vibrations during the middle ear surgery. The device resembled a pen and consisted of a reusable main body and a disposable sensitive head including piezoelectric polymer sensor. Almost all of components of the device were made of polymer for light weight and for acoustic impedance matching to the middle ear system. Several frequencies can be analyzed simultaneously and several measures can be taken by time. The results showed that the device can record normal and reconstructed ossicular chain vibration in response to an acoustic stimulation, with similar results to those achieved by laser Doppler vibrometer. This light, handheld and low-cost device allows fast, easy and safe assessments of normal ossicular chain mobility and ossicular chain reconstruction efficiency. Primary pre-clinical trial showed very promising performance of the device that could be used to qualitatively control ossiculoplasty during real-time surgical procedure. Clinical assessments will be done to further evaluate the real-life performance of the device.

Sensor Piezoeléctrico con Geometría Lineal para Tomografía Optoacústica: Implementación y Caracterización Eléctrica

En este trabajo se presenta la implementación y caracterización eléctrica de un sensor polimérico piezoléctrico de banda ancha con geometría lineal, basado en una película delgada de fluoruro de polivinilideno. Se midió la impedancia eléctrica del sensor en función de la frecuencia, encontrándose que el polímero prácticamente no fue alterado por el proceso de fabricación del sensor. Además, se estudió la respuesta en frecuencia del sensor con un amplificador de transimpedancia, observándose una marcada reducción del ancho de banda del sistema debida a la elevada capacitancia del dispositivo.

Parametric modeling of wideband piezoelectric polymer sensors: Design for optoacoustic applications.

In this work, we present a three-dimensional model for the design of wideband piezoelectric polymer sensors which includes the geometry and the properties of the transducer materials. The model uses FFT and numerical integration techniques in an explicit, semi-analytical approach. To validate the model, we made electrical and mechanical measurements on homemade sensors for optoacoustic applications. Each device was implemented using a polyvinylidene fluoride thin film piezoelectric polymer with a thickness of 25 μm. The sensors had detection areas in the range between 0.5 mm2 and 35 mm2 and were excited by acoustic pressure pulses of 5 ns (FWHM) from a source with a diameter around 10 μm. The experimental data obtained from the measurements agree well with the model results. We discuss the relative importance of the sensor design parameters for optoacoustic applications and we provide guidelines for the optimization of devices.

Determining a piston's top dead center (TDC) in an automobile using installed piezoelectric on a vibrating beam

Smart structures and MEMS are considered important field recently, due to the importance and high capabilities in measurement and the power of reaction and response to changes of the surroundings. This research concerns two fields of practical vision in the automotive industry and discuss the energy recycled industrial vibrations. The goal is to use the PVDF piezoelectric elements in car flywheel for energy harvesting, and compare and replace it with the revolution sensor. This research is totally based on empirical tests data and the result that the use of piezoelectric polymer sensors can harvest energy, was find performing far better than inductive sensors. Keywords: Piezoelectric element; Vibration energy harvesting; smart structures; Revolution sensor; Flywheel

A piezoelectric polymer cavitation sensor installed in an emulsion generation microchannel device and an evaluation of cavitation state

In previous works, ultrasonic emulsification was realized using small microchannel devices oscillated by piezoelectric transducers. By using the devices, the emulsification in the flow process was also realized. In these devices, the driving frequency was higher than 2 MHz. This value is higher than the maximum audible field. On the other hand, the frequency is too high to utilize the cavitation effect. This is because the cavitation threshold depends on the frequency. The aim of this study is to confirm the cavitation state in the microchannel device using a piezoelectric polymer sensor. A micropatterned cavitation detection sensor has been fabricated by a photolithography technique and evaluated in a high-intensity ultrasound field. The emulsification state in the microchannel device has been evaluated using the fabricated sensor.

Preliminary evaluation of the tactile feedback system based on artificial skin and electrotactile stimulation.

This research is motivated by the need of integrating cutaneous sensing into a prosthetic device, enabling a bidirectional communication between the amputee and the prosthetic limb. An electronic skin based on piezoelectric polymer sensors transduces mechanical contact into electrical response which is conveyed to the human subject by electrotactile stimulation. Rectangular electrode arrays are placed on each patient's forearm and experiments are conducted on five different subjects to determine how well the orientation, position and direction of single lines are recognized. Overall, subjects discriminate the different touch modalities with acceptable success rates. In particular, the direction is identified at best and longitudinal lines on the patient's skin are recognized with the highest success rates. These preliminary results assess the feasibility of the artificial skin - electrostimulation system for prosthetic applications.

3P4-7 Evaluation of a Microchannel Device for an Emulsion Generation by using a Piezoelectric Polymer Sensor

3P4-7 Evaluation of a Microchannel Device for an Emulsion Generation by using a Piezoelectric Polymer Sensor

Computational intelligence techniques for tactile sensing systems.

Tactile sensing helps robots interact with humans and objects effectively in real environments. Piezoelectric polymer sensors provide the functional building blocks of the robotic electronic skin, mainly thanks to their flexibility and suitability for detecting dynamic contact events and for recognizing the touch modality. The paper focuses on the ability of tactile sensing systems to support the challenging recognition of certain qualities/modalities of touch. The research applies novel computational intelligence techniques and a tensor-based approach for the classification of touch modalities; its main results consist in providing a procedure to enhance system generalization ability and architecture for multi-class recognition applications. An experimental campaign involving 70 participants using three different modalities in touching the upper surface of the sensor array was conducted, and confirmed the validity of the approach.

Investigation of the Effect of Weight Factor on Performance of Piezoelectric Weigh-in-Motion Sensors

Trucking industry growth increases loads on existing roads and may raise the possibility of overloaded vehicles, which consequently cause significant damage to pavement. Weigh-in-motion (WIM) technology improves weight enforcement activities by increasing the capacity of static weigh stations and provides traffic monitoring and traffic data for pavement research and design. However, there is still a lack of knowledge about the behavior of WIM sensors installed in different environments, which affects reliable and precise data gathering. Therefore, different types of piezoelectric WIM systems, including quartz, polymer, and ceramic sensors, were installed at the Center for Pavement and Transportation Technology (CPATT) test sites of the University of Waterloo in Canada. The objective of this research is to explore the behavior of piezoelectric WIM sensors under different load conditions specifically for the polarized sensors, which illustrated heteroscedasticity in weight estimations caused by inconsistent variance of estimations. The issue was solved by transformation of variables, which resulted in constructing a compensation curve. The investigated effect of the weight factor will assist in the recommendation of improved benefits of the least expensive WIM technology.

압전필름을 센서로 사용한 접촉식 계수장치 개발

This paper deals with the development of a contact-type counting device using a piezoelectric polymer film as a sensor. The piezoelectric and vibration characteristics of the film under a bending vibration were investigated theoretically and experimentally. A counting device, which includes filters, an amplifier, an analog-digital converter, and a display, was designed and fabricated. The performance of the piezoelectric polymer sensor was evaluated in the sense of the responses to contact force, contact frequency, and contact speed. The life and the temperature effect were also investigated for the piezoelectric film sensor.

Nondestructive damage detection and interfacial evaluation of single-fibers/epoxy composites using PZT, PVDF and P(VDF-TrFE) copolymer sensors

Damage sensing and interfacial evaluation of single-glass or basalt fibers/epoxy composites were performed by micromechanical technique and acoustic emission (AE). Piezoelectric lead–zirconate–titanate (PZT), polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer were used as AE sensor, respectively. In single-fiber composite, the damage sensing and interfacial properties with different sensor types were compared with each other. Piezoelectric PVDF polymer sensor was attached or embedded in the composite, whereas PZT sensor was only attached on the surface of specimen. For glass fiber/epoxy composite, the fiber fracture, matrix crack and possible interfacial debonding signals were detected by PZT sensor, whereas the fiber fracture signals were detected mainly by PVDF sensor because the sensitivity of PZT sensor was higher than that of PVDF sensor. The sensitivity of P(VDF-TrFE) copolymer sensor was rather higher compared with conventional PVDF sensor case. In case of embedded polymer sensors, responding sensitivity was higher than that of the attached case. It can be due to fully constraint inside specimen to transfer elastic wave coming from micro-deformation well.

힘 피드백 기반의 세포조작을 위한 세포막 침습력 측정

In biological cell manipulation, manual thrust or penetration of an injection pipette into an embryo cell is currently performed by a skilled operator, relying on visual feedback information only. Accurately measuring cellular forces is a requirement for minimally invasive cell injections. Moreover, the cellular force sensing is essential in investigating the biophysical properties for cell injury and membrane modeling studies. This paper presents cellular force measurements for the force feedback-based biomanipulation. Cellular force measurement system using piezoelectric polymer sensor is implemented to measure the penetration force of a zebra fish egg cell. First, measurement system setup and calibration are described. Second, the force feedback-based biomanipulation is experimentally carried out. Experimental results show that it successfully supplies real-time cellular force feedback to the operator at tens of uN and thus plays a main role in improving the reliability of biological cell injection tasks.<br/>

Finite element formulation for anisotropic coupled piezoelectro‐hygro‐thermo‐viscoelasto‐dynamic problems

A finite element algorithm has been developed for the efficient analysis of smart composite structures with piezoelectric polymer sensors or/and actuators based on piezoelectro-hygro-thermo-viscoelasticity. Variational principles for anisotropic coupled piezoelectro-hygro-thermo-viscoelasto-dynamic problems have also been proposed in this study. As illustrative studies, dynamic responses in laminated composite beams and plates with PVDF sensors and actuators are obtained as functions of time using the present finite element procedures. The voltage feedback control scheme is utilized. The proposed numerical method can be used for analysing problems in the design of smart structures as well as smart sensors and actuators. Copyright © 1999 John Wiley & Sons, Ltd.

Digital time delay network for an active underwater acoustic coating

A digital time delay system has been developed for control of an active underwater coating. The coating contains piezoelectric polymer sensors and a piezocomposite actuator encapsulated within a host polymer. Its application is to be layered onto submerged objects that desire reduction of an underwater sound reflection. The control system featured considers a time delay network as opposed to an analog phase delay approach featured in past studies [Howarth et al., J. Wave Mat. Interact. 4, 83–88 (1989); Howarth et al., J. Acoust. Soc. Am. 91, 823–831 (1991)]. The concept of the active coating control is that of an open-loop velocity feedback between sensors and actuator. This scheme prevents feedback instability because the actuator output is acoustically decoupled from the sensors. The digital time delay controller has the added benefit of parallel multichannel processing to characterize both the incident acoustic pressure and the reflected pressure. The reflected pressure is monitored at the sensors for near-field determination of the effectiveness of the active coating system prior to far-field sound radiation. Experimental results were obtained for normal incidence in a water-filled acoustic pulse tube terminated at its boundary with an active coating and air backing. Echo reduction comparisons as functions of sound reduction and bandwidth are presented.

NEW ACOUSTIC SENSORS

New developments in the field of microphones or acoustic sensors, based on the silicon, optic-waveguide, and polymer technologies are discussed. The silicon sensors are produced on silicon wafers with micromechanical methods. Subminiature transducers of this kind, utilizing the condenser or piezoelectric principles, are made with membranes of about 1 mm2 area and less than 1 µm thickness. Optic-waveguide sensors employ glass fibers or waveguides on glass or polymer substrates and detect phase or intensity modulations of the transmitted light caused by the sound waves. Polymer sensors utilize polymer electrets or piezopolymers, usually as thin membranes or layers. Polymer electret sensors find widespread applications as microphones and ultrasonic transducers. New developments include the use of electret biasing in silicon sensors and the design of electret-microphone arrays. Piezoelectric polymer sensors are being improved by the use of better materials and by innovative poling techniques, such as monomorph poling. Of interest are also hybrid sensors using silicon structures covered with piezoelectric polymer layers.

Piezocomposite coating for active underwater sound reduction

An active acoustic coating is presented for layering over objects in a fluid medium. The design of the active coating prevents an incident sound wave from reflecting off the acoustic boundary of a submerged object. The acoustic energy associated with the incident disturbance is absorbed out of the medium through a piezocomposite device in the coating and dissipated by internal electrical means. The components encapsulated inside the elastomer coating are a piezocomposite actuator and piezoelectric polymer sensors. The sensor arrangement detects and separates the acoustic field into a signal in terms of the incident acoustic pressure wave. The signal is manipulated through an electronic network to generate an appropriate driving voltage. This output drives a thickness extensional mode piezocomposite transducer (actuator) with a linear velocity profile over a broad frequency band. The actuator excitation results in a dynamic impedance matching with the incident disturbance such that the coating appears as a nonreflective acoustic surface. An advanced coating design includes an actuator that can be simultaneously driven to reduce the reflected and transmitted sound fields. Experimental results are presented for one-dimensional incident planar acoustic waves propagating in a water filled pulse tube.

Digital time delay network for active underwater acoustic coating

A digital time delay system has recently been developed for control of an active underwater coating. The active coating contains piezoelectric polymer sensors and a piezocomposite actuator encapsulated within a host polymer. The coating is for layering on submerged objects to actively reduce underwater sound reflection. The control system incorporates time delay circuitry as opposed to the analog phase delays used in previous studies. The type of control is an open‐loop velocity feedback. This system prevents feedback instability because the acoustic reflection is decoupled from the actuator. The digital controller can characterize both the incident acoustic pressure and the reflected pressure through parallel multichannel processing. The reflected pressure is monitored at the sensors for determination of the effective sound reduction. Experimental results were obtained in a water‐filled acoustic pulse tube terminated at its boundary with the active coating. Echo reduction comparisons as functions of soun...