PVDF Film Sensor Research Articles

Dynamic behaviour of cavitation bubble close to a flexible wall

The dynamic behaviour of cavitation bubble close to a flexible boundary is investigated experimentally. The cavitation bubble is produced as a consequence of an optical breakdown generated by the focus of 532 nm Nd-Yag laser beam. A gold mirror is used to focus the expanded laser beam into a spherically shaped plasma. A PVDF film sensor is used for the measurement of the interaction magnitude between the bubble and the flexible boundary. As the flexible boundary directly the PVFD film sensor is used. The sensor is flexibly mounted within a specially designed movable frame which enables to modify the elastic properties of the system. The bubble dynamics and the flexible wall movement are recorded by high-speed CCD camera and correlated with the acoustic signal obtained by the PVDF film. Different bubble collapse patters for different bubble wall distances and the corresponding acoustic signals are presented.

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor.

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, with its peak locomotion speed reaching 150 cm/s. First of all, we observed the microstructure and hierarchy of water strider legs using the scanning electron microscope. On the basis of the observed morphology of the legs, a theoretical model of the detachment from water surface was established, which explained water striders' capability to slide on water surface effortlessly in terms of energy reduction. Secondly, a dynamic force measurement system was devised using the PVDF film sensor with excellent sensitivity, which could detect the whole interaction process. Subsequently, a single leg in contact with water was pulled upward at different speeds, and the adhesion force was measured at the same time. The results of the departing experiment suggested a deep understanding of the fast jumping of water striders.

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

Calibration of PVDF Film Transducers for the Cavitation Impact Measurement

This paper describes investigation of the influence of the protective layer thickness on the calibration sensitivity of PVDF films sensors for the cavitation impacts measurements. The PVDF film sensor is casted into an aluminium block. The drop ball method is used for the measurement of the relation between impact force and the voltage detected on the PVDF film sensor. The calibration constants are measured for three different protective layers thicknesses. Five different ball weights for 400 mm drop height are used to reach the required impact force range. The ball positions for the evaluation of the impact force are measured with a high speed camera. The voltage signal detected on the PVDF film clamps was measured with a high speed digitizer. The measured signals are analysed in LabVIEW Signal Express.

On-line Vibration Monitoring and Analysis of Thin-walled Workpiece Based on PVDF Film Sensor in Milling Process

On-line Vibration Monitoring and Analysis of Thin-walled Workpiece Based on PVDF Film Sensor in Milling Process

Design of efficient loadcell for measurement of mechanical impact by piezoelectric PVDF film sensor

Conversion efficiency of mechanical impact into electrical voltage remains ever increasing demand for piezoelectric PVDF film sensor. For a given film sensor, the output voltage produced due to mechanical impact is highly dependent on the direction of stretching (or compressing) and active area of the film sensor. More is the active area of the film; higher will be the output voltage. It is shown that the active area is significantly increased due to the ridge-like shape given at the inner surfaces of the plates of sandwich type loadcell and as a result of which higher conversion efficiency is obtained. The effectiveness of the ridge-like shape is confirmed statistically by conducting two factorial design of experiment in which shape and material of the loadcell are considered as the two factors with 2×4 matrix. In case of loadcell made of glass plates, more than 100% increase in the output voltage is observed for ridge-like shape in comparison to its plain counterpart. Both the bandwidth and frequency range of the output signal is found to be independent and dependent of the loadcell materials for indirect and direct impact with the loadcell respectively. The merits and demerits of the fabricated loadcells are discussed.

High Signal-to-Noise Ratio Phonocardiogram using a Shielded PVDF Film Sensor

A shielded PVDF Film sensor has been used to obtain the Phonocardiogram (PCG) with high Signal-to-Noise Ratio (SNR). A very simple circuit is good enough to detect the first (S1) and the second (S2) sound of the PCG without using any digital signal processing technique. The mechanical coupling between the sensor and the subject determines the kind of signal detected. The sensor has been mounted on the membrane of a mechanical stethoscope in order to simplify the location of the best auscultation area on the chest. If the sensing area of the PVDF Film is in direct contact with the membrane (or the skin), the sensor detects the mechanical displacements of the heart contractions and respiration, so the PCG could not be detected. The best option to detect the S1 and the S2 is to leave an air gap between the sensor and the membrane. Despite using a shielded sensor, it is also necessary to shield electrically the circuit to reduce power line interference, which could not be filtered because it is in the frequency range of S1 and S2. The PCG and the lead II ECG have been measured on ten volunteers. Bland-Altman plots compares the time interval (beat-to-beat) between the peaks of the S1 and S2 with the RR interval of the ECG. The mean bias obtained is not greater than 0.75 ms, which is negligible. With the SNR obtained (>55 dB), it is possible to detect some valves diseases using a real-time comparison between the PCG and the ECG.

A new layered sensor for simultaneous measurement of EMG, MMG and oxygen consumption at the same position.

A new layered sensor for simultaneous measurement of electromyography (EMG), mechanomyography (MMG) and oxygen consumption based on near-infrared spectroscopy (NIRS) at the same position of the muscle is presented. The proposed sensor is a layered structure of a thin stainless-steel electrode, a PVDF film with transparent electrodes and optical sensors. EMG, MMG and oxygen consumption based on NIRS are measured by the stainless-steel electrodes, PVDF film and optical sensors, respectively. Using the three types of data, muscular activity can be analyzed in more detail. Additionally, the proposed sensor system reduces the constraint of the sensors arranged on the skin in measurements at multiple points because three types of information, previously obtained with three types of general sensors, are detected by a pair of proposed sensors. In an experiment, simultaneous measurement of EMG, MMG and oxygen consumption via NIRS at the forearm was demonstrated using the proposed sensor under fluorescent light. The performance of the layered sensor was evaluated.

148 脈診における脈波同時計測システムの開発 : カフを用いたPVDFフィルムセンサによる脈波計測の定量化

148 脈診における脈波同時計測システムの開発 : カフを用いたPVDFフィルムセンサによる脈波計測の定量化

Study on crack detection of civil infrastructures by using PVDF film sensor

Study on crack detection of civil infrastructures by using PVDF film sensor

PVDF 필름 내장 탄성벨트를 이용한 운동강도 모니터링

Pedometer, tri-axial accelerometer, and measuring system of <TEX>$CO_2$</TEX> generated during metabolism have mainly been used to measure the quantity of motion and inhaling capacity while walking or running. However, these sensors are heavy, expensive, and uncomfortable to wear and difficult to check the work-out condition. In an attempt to overcome these limitations, a soft, flexible, and lightweight piezoelectric polymer-based sensor has been prepared. The PVDF film sensor with thin silver-paste layers in both sides was coated with silicon rubber to amplify stress by the external power such as tension and pressure. Thus, movement of thigh muscles was monitored and physical activity was predicted during walking and running, with an elastic belt embedded with the prepared PVDF film sensor, which was named as a physiological sensing belt (PSB), strapped on the thigh.

EMI 차폐능을 갖는 PVDF 필름 내장 탄성벨트를 이용한 호흡 모니터링

The poled PVDF film sensor with thin silver electrode on both surfaces was coated with conductive carbon paste followed by silicon elastomer/carbon black mixture coating. This process gave it EMI shielding as well as enhanced toughness. The physiological sensing belt(PSB) for respiration monitoring was made by embedding the silicone rubber/carbon black/conductive carbon layer coated PVDF film between elastic textile bands. The sport bra having PSB could be well applied to respiration monitoring for the woman wearing it with very low motion artifact even during walking and running.

APPLICATION OF PIEZOELECTRIC MATERIAL FILM PVDF (Polyvinylidene Flouride) AS LIQUID VISCOSITY SENSOR

&lt;p&gt;The use of piezoelectric materials in sensors and transducers are growing rapidly. This material can be applied in many ways. One of Piezoelectric material founded in market was sheet- shaped called PVDF film. PVDF film applications in sensors allow the use in many application. In this study, PVDF film is used as the liquid viscosity sensor using the principle of concentric cylinders. This research aims to design a sensor with a mechanical sensor that can be used for viscosity. In this study, the mechanical and electrical parts of the sensor was designed so that it can be used as a viscosity sensor. The design begins with designing the mechanical sensor consisting of a cylinder with diameter of 3 cm which at the upper end of the shaft mounted a circular plate as a place to attach the PVDF film sensor. This cylinder will be immersed in the outer cylider of 5 cm in diameter filled with test fluid. This outer tube is rotated so that the liquid then follow to spin, the test fluid spin will be rubbing against the cylinder resulting a force and torque on the cylinder. This force will be forwarded to the shaft and up to the plate that has been attached PVDF film. Due to this force, the PVDF electrode charge will arise. This charge by a charge amplifier is converted into a voltage proportional to the force felt by the inner cylinder. Viscosity will affect the force that drive PVDF film so that by measuring the output voltage will obtain the viscosity of the test fluid.&lt;br /&gt;Research was done by taking 10 samples of oil and 3 different size ofPVDF film and a strain gage,that are: 1 cm x 3 cm (PVDF1); 1 cm x 2 cm (PVDF2); 1 cm x 1 cm (PVDF3). Results showed that the resolution of PVDF1, PVDF2 and PVDF3 are 4.6 mv/cPois; 3.1 mv/cPois and 1.5 mv/cPois respectively, while the strain gage produce a resolution of 1.2 mv/cPois. The average resolution of PVDF is 1.53 mv.cPois-1.cm-2, which means that every 1 cm2 PVDF film area and the increase of 1 cPois of viscosity of the material will produce 1.53 millivolts.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;&lt;br /&gt;&lt;/p&gt;

Investigation of the Transient Behavior of a Cantilever Beam Using PVDF Sensors

In this paper, a PVDF film sensor was used to measure the transient responses of a cantilever beam subjected to an impact loading. The measurement capability of a PVDF sensor is affected by the area of the PVDF film sensor and the signal conditioner (charge amplifier). The influences of these effects on the experimental measurements were investigated. The transient responses for the dynamic strain of the beam were measured simultaneously by the PVDF sensor and a conventional strain gauge. The resonant frequencies of the beam were determined by applying the Fast Fourier Transform on transient results in the time domain of the PVDF sensor and the strain gauge. The experimentally measured resonant frequencies from the PVDF sensor and the strain gauge were compared with those predicted from theoretical and FEM numerical calculations. Based on the comparison of the results measured for these two sensors, the PVDF film sensor proved capable of measuring transient responses for dynamic strain, and its sensitivity is better than that of the strain gauge. Furthermore, almost all the resonant frequencies can be obtained from the results of transient responses for PVDF film.

Measurement of the impuslive force generated by colapsing bubble close to a solid boundary

The article presents experimental results of the acoustical and optical study of cavitation bubble collapse close to a solid boundary in water. The bubble was generated by discharge of low-voltage capacitor into a couple of wires closing a simple circuit. Different distances from the solid wall and different maximum bubble radii were studied. The bubble radius was studied using time-resolved photography and by PVDF film sensor glued on the solid boundary. The illumination was provided by high-power led diode. Synchronization of the system was provided by pulse generator connected to an oscilloscope. The impact power of the bubble to the wall was estimated from the time-resolved photography of the bubble and from the PVDF film sensor signal. The PVDF film sensor calibration was performed by a pendulum test to estimate the impact force.

Application of PVDF Film Sensor to Detect Early Damage in Wind Turbine Blade Components

Monitoring technique for detection of early damage in the wind turbine blade has been investigated using PVDF film sensor and strain gages. The trailing edge component with shear web was prepared by sectioning the full-scale blade with a box spa. Several PVDF film sensors with dimension of 10x10x0.054 mm3 and strain gages were installed on shear web and skin of the component and the behaviour of these sensors were examined under opening and closing loads. From the test, optimal location for detecting the occurrence of damage with static loading was investigated and sensitivity of the PVDF sensors location to the damage was examined. With increasing the applied load, several pop-ins happened up to final failure. The outputs of the PVDF film sensors under quasi-static loads showed the relatively insignificant magnitude and peaks corresponding to pop-ins. So, it is found that PVDF film sensors mounted on the trailing edge component give an early response remarkably to the damage occurrence irrespective to the closing and opening loads. Therefore, it can be said the PVDF film sensors may be significantly useful in detecting the instance of damage occurrence in the trailing edge component. Further, it can be recommended that the relatively good location of the PVDF sensor to detect the damage in the trailing edge component be the locations free to the geometrical constraint, like the center of spar web and the blade skin remote from the joint between the spa cap and the shear web.

Characterization of a large-area PVDF thin film for electro-mechanical and ultrasonic sensing applications

Large-area PVDF thin films have been prepared and characterized for quasi-static and high frequency dynamic strain sensing applications. These films are prepared using hot press method and the piezoelectric phase (β-phase) has been achieved by thermo-mechanical treatment and poling under DC field. The fabricated films have been characterized for quasi-static strain sensing and the linear strain–voltage relationship obtained is promising. In order to evaluate the ultrasonic sensing properties, a PZT wafer has been used to launch Lamb waves in a metal beam on which the PVDF film sensor is bonded at a distance. The voltage signals obtained from the PVDF films have been compared with another PZT wafer sensor placed on the opposite surface of the beam as a reference signal. Due to higher stiffness and higher thickness of the PZT wafer sensors, certain resonance patterns significantly degrade the sensor sensitivity curves. Whereas, the present results show that the large-area PVDF sensors can be superior with the signal amplitude comparable to that of PZT sensors and with no resonance-induced effect, which is due to low mechanical impedance, smaller thickness and larger area of the PVDF film. Moreover, the developed PVDF sensors are able to capture both A 0 and S 0 modes of Lamb wave, whereas the PZT sensors captures only A 0 mode in the same scale of voltage output. This shows promises in using large-area PVDF films with various surface patterns on structures for distributed sensing and structural health monitoring under quasi-static, vibration and ultrasonic situations.

ECG와 호흡 측정이 가능한 모바일 헬스케어 의류 시스템

대부분의 모바일 웨어러블 헬스케어 모니터링 의류 시스템은 생체신호를 측정할 수 있는 센서와 데이터 취득과 무선 통신 및 제어를 담당하는 회로부, 이들을 내장하는 의복으로 구성된다. 기존의 의복형 헬스케어 시스템은 센서를 의복에 장시간 내장하기가 어렵고, 피부 접촉 시 시간에 따라 저항 값이 변화하기 때문에 장기적인 생체 신호 모니터링이 쉽지 않으며, 센서 전극과 회로 사이에 존재하는 신호선의 물리적 장애 요인도 가지고 있다. 본 연구에서는 이러한 문제점들을 해결하기 위하여, PVDF에 PEDOT 재료를 코팅하여 만든 패브릭 나노웹 ECG 전극과 PVDF 필름을 사용한 호흡 센서를 <TEX>$10\;{\mu}m$</TEX> 두께의 디지털 실을 이용하여 사용자의 의류와 일체화하였다. 탈부착이 가능한 무선 블루투스(Bluetooth) 내장 스테이션과 디지털실로 기존 의류와 일체화한 생체 신호 측정용 의류 제작을 통해, 휴대폰에서 손쉽게 심전도(ECG)와 맥박신호를 표시 할 수 있었다. Most wearable system for mobile healthcare applications consists of three parts. The first part is the sensing elements based on bio-signal, the second is the circuit module for control, data acquisition and wireless communication and control and the third is garment with a built-in electrodes and circuits. The existing healthcare garment systems have to find a solution to signal-wire and uncomfortable and inappropriate electrode to long-term attachment. Even if the wireless communication is used for healthcare garment system, the interface between sensors and circuits have to use wires. To solve these problems, this paper use electrode using PEDOT coated PVDF nanoweb for ECG signal and PVDF film sensor for respiratory signal. And, we constructed garment network using digital yarn of 10um, and transmitted ECG and respiratory signal to mobile phone through the integrated circuit with bluetooth called station To evaluate feasibility of the proposed mobile healthcare garment system, we experimented with transmission and measurement of ECG and respiratory signal using nanoweb electrode and digital yarn. We got a successful result without noise and attenuation.

A NOVEL PIEZOELECTRIC PVDF FILM-BASED PHYSIOLOGICAL SENSING BELT FOR A COMPLEMENTARY RESPIRATION AND HEARTBEAT MONITORING SYSTEM

ABSTRACT Human heartbeat and respiration signals were measured from a DAQ board interfaced with a homemade voltage-amplifier with specific frequency filtering function using an elastic textile belt imbedded with a poled-PVDF film, which is designated as a physiological sensing belt (PSB), as a piezoelectric sensor and analyzed. PSB sensor systems can be easily tied on the chest, abdomen, head, wrist, or ankle for comfortable fit. The sensitivity of the imbedded PVDF film sensor is highly dependent on the thickness of coated silicon rubber layer on both sides of the PVDF film. Both respiration and heartbeat signals could be isolated from the mixture signal measured from the chest and abdomen during respiration and pulse wave velocity could be calculated using time delay obtained from waveforms measured simultaneously at the two different body positions. Finally we found the feasibility of applying the PSB as a complementary respiration monitoring system to the traditional anesthesia activities or other types of patient respiratory monitoring such as polysomnography and telemedicine.

Piezoelectric film attached suspension for detecting disk flutter and reducing track misregistration

To increase the recording density of hard disk drives, high accuracy of head positioning is required. But disk flutter, which is airflow induced vibration, is a major contributor to head positioning error. For detecting disk flutter, we proposed a suspension to which a PVDF film sensor was attached, and built the suspension into an actual HDD. Comparing the power spectrum of disk vertical vibration with that of the PVDF film sensor output, disk flutter was well detected. We also implemented a feedforward controller and confirmed that the influence of disk flutter on position error signal is considerably suppressed.