Piezo System Research Articles

The influence of lowing the Schottky barrier on the reactive oxygen species formation in Ag@SrBi2Ta2O9 piezocatalyst under ball milling

Loading noble metal nanoparticles on piezoelectric substrates to form the Schottky barrier is believed to be an effective way to promote charge separation and enhance the piezocatalytic performance. The presence of the exceeded Schottky barrier would influence the generation of reactive oxygen species (ROS). However, the detailed correlation between the Schottky barrier height and the type of ROS is not well established. Herein, a type of Aurivillius material, SrBi2Ta2O9 (SBTO) and its composite materials Ag loaded SBTO (Ag@SBTO), were synthesized for different bacteria inactivation and pollutants degradation under ball milling (BM). The results showed that Ag@SBTO3 (0.76 wt% Ag) could lead 7.46 log10 of E. coli K12 inactivation, which was 21.3 times higher than that of SBTO. And Ag@SBTO3 also can achieve about 98.05% of Oxytetracycline degradation, while SBTO showed a better efficiency in Minocycline Hydrochloride and Rhodamine B degradation, the degradation efficiency can reach up to 92.60% and 75.04%, respectively. The variety of catalytic efficiency can be attributed to the different Schottky barrier height and the reduced activation energy of the piezo system when they were subjected to BM effect, which ultimately changed the type of ROS. Our results confirmed that ·OH and ·O2– were the main ROS for SBTO and Ag@SBTO3 during the experiments, respectively, and BM lowering the Schottky barrier of Ag loading piezoelectric material was a facile strategy to generate different ROS for a wide range of applications in water pollution control and drinking water safety.

Development of a piezo stack – Laser doppler vibrometer sensing approach for characterizing shear wave dispersion and local viscoelastic property distributions

Laser Doppler vibrometry and wavefield analysis have recently shown great potential for nondestructive evaluation, structural health monitoring, and studying wave physics. However, there are limited studies on these approaches for viscoelastic soft materials, especially, very few studies on the laser Doppler vibrometer (LDV)-based acquisition of time–space wavefields of dispersive shear waves in viscoelastic materials and the analysis of these wavefields for characterizing shear wave dispersion and evaluating local viscoelastic property distributions. Therefore, this research focuses on developing a piezo stack-LDV system and shear wave time–space wavefield analysis methods for enabling the functions of characterizing the shear wave dispersion and the distributions of local viscoelastic material properties. Our system leverages a piezo stack to generate shear waves in viscoelastic materials and an LDV to acquire time–space wavefields. We introduced space-frequency-wavenumber analysis and least square regression-based dispersion comparison to analyze shear wave time–space wavefields and offer functions including extracting shear wave dispersion relations from wavefields and characterizing the spatial distributions of local wavenumbers and viscoelastic properties (e.g., shear elasticity and viscosity). Proof-of-concept experiments were performed using a synthetic gelatin phantom. The results show that our system can successfully generate shear waves and acquire time–space wavefields. They also prove that our wavefield analysis methods can reveal the shear wave dispersion relation and show the spatial distributions of local wavenumbers and viscoelastic properties. We expect this research to benefit engineering and biomedical research communities and inspire researchers interested in developing shear wave-based technologies for characterizing viscoelastic materials.

Settings of a monolithic piezoelectric filter on bulk acoustic waves by ion-beam etching

The process of tuning of the piezoelectric filter consists in lowering the frequencies of the resonators as a result of removing the electrode layer by means of ion-beam etching (IBE) in an inert gas atmosphere. It is necessary to control frequencies of the first and second resonators, as well as the frequency spacing (distance between frequencies of the upper and lower resonances of the piezo system), dynamic impedance of partial resonators and insertion attenuation. We present the results of using ion-beam etching in tuning monolithic piezoelectric filters on volumetric acoustic waves. It is shown that tuning should be performed using frequencies of the upper and lower resonances of the piezo system under control of the insertion attenuation. It is also necessary to exclude the control operations for the frequencies of the first and second resonators. The optimum parameters of ion-beam etching electrodes of the resonators are determined: working pressure — 1.33 × 10–5 Pa, working gas flow — 1.75 m3 · Pa/sec, ion beam energy — 1 keV, ion current density — 6 mA/cm2. Moreover, the dependence of the insertion damping and dynamic resistance on the frequency of the resonator was revealed. Characteristics of the obtained monolithic quartz filter are presented: nominal frequency — 21400.681 MHz, bandwidth by –3 dB — 32.66 kHz, insertion loss 0.5 dB. The obtained results can be used when tuning sections with smaller electrodes for filters at higher frequencies.

Neural Regeneration in Dry Eye Secondary to Systemic Lupus Erythematosus Is Also Disrupted like in Rheumatoid Arthritis, but in a Progressive Fashion.

Our objective in this study was to analyze the aberrant neural regeneration activity in the cornea by means of in vivo confocal microscopy in systemic lupus erythematosus patients with concurrent dry eye disease. We examined 29 systemic lupus erythematosus patients and 29 age-matched healthy control subjects. Corneal nerve fiber density (CNFD, the number of fibers/mm2) and peripheral Langerhans cell morphology were lower (p < 0.05) in systemic lupus erythematosus patients compared to the control group. Interestingly, corneal nerve branch density, corneal nerve fiber length, corneal nerve fiber total branch density, and corneal nerve fiber area showed a negative correlation with disease duration. A negative correlation was also demonstrated between average corneal nerve fiber density and central Langerhans cell density. This is in line with our hypothesis that corneal somatosensory terminal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk not only disrupts regeneration and keeps transcription activated, but could lead to Piezo1 downregulation and cell activation on Langerhans cells when we consider a chronic path. Hence, Piezo2 containing mechanosensory corneal nerves and dendritic Langerhans cells could also be regarded as central players in shaping the ocular surface neuroimmune homeostasis through the Piezo system. Moreover, lost autoimmune neuroinflammation compensation, lost phagocytic self-eating capacity, and lost transcription regulation, not to mention autoantibodies against vascular heparin sulfate proteoglycans and phospholipids, could all contribute to the progressive fashion of dry eye disease in systemic lupus erythematosus.

Piezoelectric energy harvesting from rail track vibration using frequency up-conversion mechanism

Piezoelectric energy harvesting has great powering potential in railway applications, but current piezoelectric literature for rail track vibration mainly focuses on a single piezoelectric element or piezoelectric cantilever, whose output power is usually at the level of µW. In this work, a piezo stack energy harvester using the frequency up-conversion method with attractive magnetic force is proposed and experimentally validated for harvesting energy from rail track vibration. It consists of two parts, an inertial mass system and a piezo stack system. The frequency up-conversion mechanism is realised by allowing the inertial mass to attach and detach the piezo stack transducer periodically with the help of the attractive magnetic force. The attractive magnetic force contributes to the collision between the two systems, especially when the excitation frequency is near the resonant frequency. A theoretical model of the proposed energy harvester considering the colliding motion and magnetic force is established. A prototype is fabricated and can generate a peak power of 96.69 mW and average power of 2.59 mW at an input acceleration of 1 g applied at 9 Hz with an optimum load impedance of 200 Ω.

Lean Blowout Sensing and Processing via Optical Interferometry and Wavelet Analysis of Dynamic Pressure Data

This paper introduces a novel approach to monitor combustion instabilities in turbomachinery. This innovation is motivated by the need to better analyze flame health in a continuous flow machine, and more precisely in its hot core expressed by machine OEMs and end-users. This improved monitoring system will support an optimization of the machine performance, leading to a safer, cleaner, more flexible and more cost-efficient operation for the end-user. There have been several numerical studies that simulate the nonlinear dynamics of flame instabilities limit in simple combustors, they predict the pressure oscillations frequency is very low 5-25 Hz. Nowadays, in gas turbine monitoring, dynamic pressure measurement sensors are based on electrical working principle technologies such as piezoelectric, piezo-resistive and capacitive measurement. While exposed to high temperatures, due to pyro-electric effects and noise spectral density of charge amplifiers, piezo sensors signal to noise ratio (SNR) decreases sharply at low frequencies (about a factor 10 every 100°). Optical sensing systems provide much better stability, in the low frequency range when exposed to high temperature and, moreover, are intrinsically insensitive to vibration or EMI perturbation. This feature allows analyzing more accurately low frequency flame dynamics. Within the frame of a joint study between Meggitt, Combustion Bay One e.U. and FH Joanneum GmbH, the behavior of an optical measurement system was tested under different combustion instability conditions. By acting on system parameters (equivalent ratio, air speed) several tests have been conducted where combustion has been driven to different instability conditions such as premixed to diffusion flame transition, lean blow out, flashback. Data have been recorded and analysed from both the optical and the piezo sensors installed within the combustion chamber. The objective of the test campaign is twofold: compare optical to piezo system performances under flame combustion instabilities and, taking advantage of improved low frequency SNR of pressure data coming from optical sensors, to develop and validate an algorithmic strategy to detect/prognose phenomena such as Lean Blow Out and Flashback. The paper initially describes the principia of the used optical sensing technology, including some relevant hardware and software aspects of the measurement chain. After that, the experimental set-up and tests conditions are presented. About piezo to optical data comparison, SNR analysis of test data confirms the expectations of a lower noise at low frequency and the improved visibility of flame instabilities provided by optical sensor. Based on this, in order to analyze the transient behavior at low frequencies associated to flame instabilities two algorithmic strategies have been developed: wavelet analysis and chaos dimension analysis. Based on these methodologies several Lean Blow Out indicators have been implemented and tested. Details of their behavior in response to the variation of the equivalence ratio close to the flame blow out are presented and discussed. Three of the proposed indicators, under the investigated test conditions, proved to possess the capability to detect the blow out event. Depending on how the approach to the blow out event occurs, some indicators also shown prognostics capability. Results show some indicators start reacting as the flame approaches to extinction or as the equivalence ratio reduces. These indicators can be considered flame health meters. The test campaign results shown in the paper allow to conclude that optical sensing technologies provide advantages over piezoelectric sensing technologies such as: insensitivity to pyro-electric effects and inherent insensitivity to external perturbations, i.e. electromagnetic interferences and radio frequency interferences, vibrations. Particularly the improved accuracy at low frequencies of the sensor coupled with new signal processing techniques, as the ones presented, may support a flame health monitoring capability and the ability to sense blowout precursors. The replacement of piezo-electric with fiber optic sensors will therefore be desirable for many combustion monitoring applications, especially the ones requiring monitoring of low frequencies. This can, provide significant payoffs in engine reliability and operability, in enabling optimal performance over extended time periods as an engine ages, in reducing maintenance costs, and in increasing engine life.

Estimation of Lorentz force detuning and its compensation on 650 MHz βg = 0.92 single cell SCRF cavity

Superconducting technologies are widely used in modern radiofrequency (RF) cavities for particle accelerators in various fields of applications. The Superconducting radiofrequency (SCRF) cavities are highly sensitive to small perturbation on cavity dimensions. The operation of the superconducting cavity becomes challenging due to narrow resonance bandwidth on account of a very high-quality factor. The main perturbing source is Lorentz Force acting on the cavity wall, which detunes the cavity from resonance. Finite element (FE) analysis has an important role in Lorentz force detuning (LFD) estimation, which requires coupled-field FE analysis between the structural and RF domains of the cavity. The LFD effect can be mitigated up to a certain extent by using a proper fast tuning methodology. This paper represents the methodology for structural-high frequency electromagnetic coupled field simulation for LFD calculation of 650MHz, βg = 0.92 single-cell SCRF cavity. First, the static LFD is calculated for various voltage gradients of SCRF cavity structure and then dynamic behavior of cavity due to LFD pressure pulse is studied at different pulse widths (PW) and pulse repetition rates (PRR). A comparison of transient FE analysis of the single-cell cavity with one end fixed and another end free and cantilever beam for similar loading is done for benchmarking. To counter the detuning effect, the SCRF cavity employs a piezo tuning device. The dynamic behavior of piezo pulse response on the cavity is also studied. An experimental test of the piezo tuner system has been performed at room temperature to validate the FE coupled simulation. Further, dynamic analysis has been carried for the combined effect of LFD pressure and piezo load pulse to compensate for the LFD effect. Optimizing the piezo load for compensating the frequency shift is also discussed and based on optimum load, LFD has been mitigated for different acceleration gradients.

Determination of the sleep-wake pattern and feasibility of NREM/REM discrimination using the non-invasive piezoelectric system in rats.

The piezoelectric cage-floor sensors have been used to successfully dissect sleep patterns in mice based on signal features related to respiration and body movements. We studied performance of the piezoelectric system to quantify the sleep-wake pattern in the rat over 7days of recording compared with a visual electroencephalogram/electromyogram scoring, and under two light/dark (LD12:12 and LD16:8) photoperiods leading to change in the 24-hr sleep characteristics (N=7 per group). The total sleep time (%/24hr) over the 7days recording and hourly sleep time over the last 24-hr recording were not statistically different between methods under the two photoperiods. Both methods detected higher total sleep time with the LD16:8 photoperiod compared with LD12:12 (p<.05), and correlated significantly (p<.001) at light and dark periods during each photoperiod. The accuracies for discrimination of sleep-wake patterns between methods were 81.9% and 84.9% for LD12:12 and LD16:8, respectively. In addition, spectral analysis of the respiratory signal given by piezo during all 10-s periods of the corresponding non-rapid eye movement and rapid eye movement sleep periods recorded by electroencephalogram/electromyogram resulted in selection of 36 features that could be inserted in an automated non-rapid eye movement sleep and rapid eye movement sleep classification, with 90% accuracy with the electroencephalogram/electromyogram visual scoring. The piezo system proved to be a reliable non-invasive alternative to electroencephalogram recording to study total sleep time in rat, with feasibility to discriminate between non-rapid eye movement and rapid eye movement sleep stages. This will be interesting in pharmacological or bio-behavioural studies evaluating sleep patterns or the restorative functions of sleep in the body and the brain.

Characterization of energy consumption of new piezo actuator system used for hydraulic on/off valves

This paper presents a newly developed four-way digital piezo valve system composed of four high-response on/off piezo valves. The main part of the new on/off piezo valves introduces the piezo actuator system, which can be used instead of conventional solenoids. One of the important aspects related to the energy consumption of hydraulic linear drives is the use of energy-efficient hydraulic valves that require low switching energy and low holding power consumption. The first part of the paper presents the theoretical background of piezo technology, which is very important for understanding the properties of piezoelectric actuators. It is followed by a detailed description of the new piezoelectric actuator system used in on/off valves and four-way digital piezo valve system. The main part presents a thorough experimental analysis of the electrical energy consumption of the new piezoelectric actuator system, which can be used both as an actuator of hydraulic high-response on/off valves as well as an energy-efficient micropositioner. To validate the electrical switching energy and the holding power consumption of the new piezoelectric actuator system, several existing on/off valves were used as reference. The experimental analysis shows a huge reduction of electrical energy consumption when using the new piezo actuator system for hydraulic on/off valve actuation. Especially the holding power consumption in the stationary active state is about 6 times lower compared to other hydraulic on/off valves.

RF commissioning of the compact energy recovery linac superconducting cavities in pulse mode

At the KEK compact energy recovery linac (cERL), a new beam line to produce radioisotopes (RIs) was constructed. To increase the beam energy for RI production, we proposed to switch the operation mode from continuous-wave mode to pulse mode. The first commissioning test of the cERL superconducting radio frequency (RF) cavities operated in pulse mode was therefore carried out. The RF pulse pattern for each cavity was carefully selected according to the corresponding cavity’s loaded Q and the capabilities of the power sources. A modified feedforward table was applied to reduce the peak reflected power at the power coupler. In addition, a filling on resonance approach that aims to reduce the required incident power during the filling time due to the existence of the Lorentz force detuning was adopted. The slow drift of the pulse-to-pulse detuning on the flat top of an RF pulse was successfully compensated for by a piezo feedback system. In this paper, we present the results related to the cERL pulse mode operation. The measured RF stabilities and beam energy stability in the cERL beam commissioning are presented as well.

Design of sustainable pedestrian power generator using Piezo electric sensors

Background/Objectives: The generation of electrical power and its utilisation is an essential practice. Currently, the energy sources are non-renewable and expensive; the demand for electric power is increasing rapidly. In this purposed work, energy is generated by pedestrian power or using locomotive pressure energy. Methods/Statistical analysis: We use a tile containing several piezoelectric transducers arranged in a series-parallel configuration so as stress or pressure applied by pedestrians can be converted in useful Electrical source. DC, AC filters and buck converters are used for smoothing purpose and to obtain required voltage level. Findings: We generated approximately 20 volts by applying the pressure of the human body on the multiple piezo tiles using anti-diodes, and the highest voltage was recorded of 45 volts without using anti-diodes. Novelty/Applications: The production and life of piezoelectric transducers has been enhanced and more wattage power is generated than existing designs. The power generated can be used directly; also, we used batteries to store power. This piezo system can be fixed in homes, schools, universities and anywhere where human movements occurr. Keywords: Piezoelectric; piezo transducers; renewable energy; pressure

Effects of a Novel Piezo Actuator-driven Pulsed Water Jet System on Residual Kidney After Partial Nephrectomy in a Rat Model

To evaluate renal damage after off-clamp partial nephrectomy (PN) using a novel surgical device, piezo actuator-driven pulsed water jet (ADPJ) system. Sprague-Dawley rats were divided into 4 groups and subjected to sham operation, off-clamp PN by the piezo ADPJ system, radio knife, and soft coagulation, which have been used as thermal coagulation devices. Urine and blood samples were collected, and residual kidneys were harvested at 1, 7, 14, 30, and 90 days after PN. Serum blood urea nitrogen, creatinine, and urinary and serum kidney injury molecule-1 KIM-1 levels were measured. Morphological features and the extent of renal ischemia of resection surfaces were evaluated by hematoxylin-eosin staining and immunostaining using antibodies to 1-methyladenosine, respectively. In addition, the expression levels of KIM-1 mRNA extracted from each resection surface were analyzed by quantitative real-time reverse transcription polymerase chain reaction. Serum blood urea nitrogen and creatinine were significantly lower with the piezo ADPJ system than with soft coagulation. Urinary and serum KIM-1 levels were also significantly decreased with the ADPJ. The extent of 1-methyladenosine immunostaining was significantly less with the ADPJ than with thermal coagulation devices. The expression levels of KIM-1 mRNA were also lower in the ADPJ system group. The piezo ADPJ system might attenuate renal damage after off-clamp PN.

Experimental analysis of functional requirements to exceed the 100 kW/l in high-speed light-duty diesel engines

The paper describes the results achieved in an experimental study aimed at identify the operating parameters, in terms of fuel injection characteristics, intake/exhaust conditions and thermomechanical stress of engine and turbocharger, required to exceed the high threshold of 100kW/l for light-duty high speed diesel engines. In order to increase the power/weight-volume ratio, such target is currently one of the milestones for diesel engine development engineers.To achieve the specific power target a high-performance prototype 0.5 l single-cylinder engine demonstrator was developed employing some special very robust components and high-quality parts from the state-of-art automotive diesel technology. A prototype advanced piezo injection system, capable of 3000bar maximum injection pressure, was employed.Geometrical features of the combustion system and injector nozzle were carefully preconfigured based on the characteristics of the most recent diesel engines developed for premium high-performance cars, as well as on the best knowledge of the authors. The operating parameters in terms of intake – exhaust conditions and injection strategy were properly parametrized in order to find the boundary conditions suitable for the desired specific power target.The paper discusses the system sensitivity to the boundary conditions of the charging and exhaust systems, and develops a balanced set of targets for the complete system based on thermo-structural, fluid-dynamic and efficiency considerations. The tests confirmed the benefits of the employment of very high fuel injection pressures as a way to face with the trade-off of combining high performance and fuel economy for light-duty high-speed diesel engines.

분사압력 1800 bar 실현을 위한 직접 니들구동방식 피에조 인젝터 설계 최적화 연구

The advantages of the common rail fuel injection system architecture have been recognized since the development of the diesel engine. In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure up to and above 2000 bar. And solenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomization. In this study, the direct needle-driven piezo injector was investigated for accomplishing injection pressure of 1800 bar by optimal design by simplification of component and changing number of springs and plates of DPI. It was found that a direct needle-driven piezo injection system features the prototype DPI for passenger vehicle to operate at 1800 bar of injection pressure.

Highly sensitive displacement measurement based on spectral interferometry and Vernier effect

A highly sensitive measurement of the displacement of an interferometer mirror based on spectral interferometry and Vernier effect is proposed and demonstrated. The displacement measurement employs two interferometers in tandem, an interferometer represented by a combination of a polarizer, a birefrigent quartz crystal and an analyzer, and a Michelson interferometer. In the setup the Vernier effect is generated and the resultant channeled spectrum is with the envelope which shifts with the displacement of the interferometer mirror. We analyze the new measurement method theoretically and show that the sensitivity of the displacement measurement based on the wavelength interrogation is substantially increased in comparison to a standard method with a Michelson interferometer. We also demonstrate the realization of the measurement setup in which the position of the interferometer mirror is controlled via a closed-loop piezo positioning system. Experimental results show that the displacement measurement can reach a sensitivity of 264nm/μm, which is substantially increased in comparison to −34nm/μm reached for a standard measurement.

자동초점에 사용되는 두 가지 Liquid Lens제어에 관한 연구

The autofocus system is automatically to drive the focus. It is very important to computer vision system. In the case of a compact camera, the actuator technology is used for auto-focus in mass production. the position sensor is required, the circuit configuration and easy method is widely used in VCM, compared to the stability of the drive size and the noise is a big stepping motor type, size has a piezo system having a humidity problem and the small leaded vulnerability. In addition, there is a liquid lens system, the advantages of low power in a compact structure but also a structure with proven quality and reliability and features required pressure. In this paper, we implement two control systems that can control the actuator as a liquid range of VCM using a sharpness of the image acquired by the image sensor automatically initiates 5Mpixel class was the implementation verification of focusing.

Experimental optimization of power-function-shaped drive pulse for stick-slip piezo actuators

Motion of a stick-slip piezo actuator is generally controlled by the parameters related to its mechanical design and characteristics of the driving pulses applied to piezoceramic shear plates. The goal of the proposed optimization method is to find the driving pulse parameters leading to the fastest and the most reliable actuator operation. In the paper the method is tested on a rotary stick-slip piezo actuating system utilized in an atomic force microscope.The optimization is based on the measurement of the actuator response to driving pulses of different shapes and repetition frequencies at various load forces. To provide it, a computer controlled testing system generating the driving pulses, and detecting and recording the corresponding angular motion response of the actuator by a position sensitive photo detector (PSPD) in real time has been developed. To better understand and interpret the experimental results, supportive methods based on a simple analytical model and numerical simulations were used as well.In this way the shapes of the single driving pulses and values of the load force providing the biggest actuator steps were determined. Generally, the maximal steps were achieved for such a combination of the pulse shapes and load forces providing high velocities at the end of the sticking mode of the actuator motion and, at the same time, lower decelerations during the slipping mode.As for the multiple driving pulses, the pulse shapes and values of repetition frequency ensuring the sticking mode of the actuator motion during the pulse rise time together with the maximum average angular rotor velocity were specified. In this way the effective and stable operation conditions of the actuator were provided.In principle, the presented method can be applied for the testing and optimization of any linear or angular stick-slip actuator.

PZT to Lead Free Piezo Ceramics: A Review

The growth of piezo science is phenomenal since the discovery of piezoelectricity in 1880. Among various piezoelectric materials, lead zirconate titanate (PZT) is a very popular and exhaustively studied piezo system which allows synthesis of large number of materials with wide range of properties due to formation of solid solutions over large range of Zr:Ti ratio. Also, this system accommodates wide range of dopants for modification of crystal structure. Due to this versatile nature, PZT has emerged as very popular among users and researchers worldwide. However, considering the toxicity of lead oxide, development of lead free piezo ceramics is encouraged in recent years. Some lead free piezo material systems such as BNT, BKT, KNN, BZT-BCT have been explored. However, development of lead free piezo devices and their performance in comparison with PZT devices are yet to be established. At this juncture, it was felt that an article reviewing the current status of development of piezo materials highlighting the change from PZT to various lead free systems would be of very much interest to the researchers. Therefore, efforts are made to bring out the recent developments on R&D of piezo materials in this review article.

A Piezo-resistive Application in Textile Design

In this study, it is aimed at that once the user carry loads over his capacity, system gives sound signal as a result work accidents can be decreased as much as possible by using piezo design application. Firstly, circuit design detecting sensor have been made in Proteus-Isis programme. Since parts of circuit can work, transfer the datas and give warning signal, foftware of system have been written in CCS c programme. Piezo system have been explained generally and work principle of design and system datas have been shared. It is showed that this prototype study can be applied and it is explained what kind of improvements can be made for future applications.

Spontaneous high piezoelectricity in poly(vinylidene fluoride) nanoribbons produced by iterative thermal size reduction technique.

We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar γ phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar γ phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 μA peak short-circuit current output.