Paint Sensor Research Articles

Voltage drift compensation in charge amplifiers for DC measurements: Application to piezoelectric paint sensors

Voltage drift over time in charge amplifiers is a problem not fully solved yet for DC measurements and continues to be a challenge for the scientific community. In this study we analyse the factors that cause this unwanted effect and propose a new method to compensate it. An automatic electronic circuit compensates the drift effect in two stages: first, a closed-loop proportional–integral control is used to bring the output voltage of the charge amplifier to zero and hold it while no measurement is being taken; and second, the voltage drift is compensated with an open-loop control when measurement is being taken. The proposed method allows us to compensate the voltage drift whatever its magnitude. Simulation and experimental results show that the drift effect in the output voltage of the charge amplifier is attenuated up to 99%.

압전 페인트 센서를 활용한 구조물 모니터링 최신 기술 동향

Recently, large-scale accidents caused by minor damage from fatigue failure and impact on structures have been frequently reported. Therefore, a real-time damage monitoring system of structures is considered to be one of the most important technologies to ensure safety in various types of research. The piezoelectric sensor, which has an advantage of converting deformation of a structure into an electrical signal without using an additional power source, has been reported as one of the most suitable methods for real-time monitoring systems. This review aims to describe the structural monitoring system utilizing piezoelectric paint sensors. First, we present the concept of a piezoelectric paint sensor with the advantages of flexibility and piezoelectric performance. Then, factors affecting the performance of the piezoelectric paint sensor are introduced. Finally, an overview of piezoelectric paint sensors for structural monitoring, such as vibration detection and impact monitoring, are provided. The state-of-the-art of the application of the piezoelectric sensor is also introduced, providing feasibility in industrial fields.

Pressure-sensitive paint measurements with temperature correction on the wing of AGARD-B under transonic flow conditions

This study experimentally examined the flow phenomena and pressure distribution on the wing of Advisory Group for Aerospace Research and Development Model B (AGARD-B) at a Mach number of 0.83. For simultaneous pressure and temperature measurement, a mesoporous pressure-sensitive paint (PSP) sensor was applied to one of the wings of AGARD-B at an angle of attack (AOA) of 0°–8° and a temperature-sensitive paint sensor was applied to the other wing. The collected temperature data were used for pixel-by-pixel temperature correction in a PSP experiment. The pressure distribution obtained on the AGARD-B wing through the PSP experiment with temperature correction agreed well with that obtained through computational flow dynamics (CFD) simulation and accurately indicated the low-pressure regions introduced by the vortex generated from the leading edge at an AOA larger than 4°. The lift coefficient calculated using the PSP data agreed well with that calculated using CFD.

Piezoelectric properties of paint sensor according to piezoelectric materials

The objective of this paper is to study the performance of piezoelectric materials on a piezoelectric paint sensor. The paper begins by presenting a fabrication method for a paint sensor with piezoelectric properties using piezoelectric materials. The paint sensor is composed of piezoelectric powder and epoxy resin in a 1:1 weight ratio. Five different piezoelectric materials, including three soft-type and two hard-type materials, were used and their piezoelectric properties compared in paint sensors and ceramic sensors. The paint sensors were cured using a steel mold for producing a uniform specimen size of 20 × 10 × 0.2 mm3, and an electrode was made on the upper and lower sides using silver paste. Poling treatment was then successfully performed at room temperature (20 °C) under a 4 kV mm−1 electric field for 30 min in order to activate the paint specimen as a sensor. Impact signals were monitored by measuring output voltage from the paint sensor in relation to impact force. The sensor’s piezoelectric properties were then calculated using normalized piezoelectric properties. In addition, five different piezoelectric ceramic sensors were fabricated and their d33 value measured to compare the sensitivity of paint sensors. As a result, Pb(Ni1/3Nb2/3)O3-Pb(Zr, Ti)O3 (PNN-PZT) powder showed higher sensitivity and higher piezoelectric properties than other piezoelectric materials in both paint and ceramic sensors.

Impact monitoring characteristics of piezoelectric paint sensor by thermal fatigue analysis for railroad vehicle applications

The strong aerodynamic drag under a railroad vehicle in motion causes the track ballast to fly up and around. The flying ballast can collide with the underside of the coach, damaging the electronics installed there. There are even cases wherein the aerodynamics of fast-moving train causes the gravel to hit the side of the coach and break the windows. Extensive and numerous studies are underway to reduce the damage caused by such phenomena. In this study, a “smart paint sensor” for impact monitoring was fabricated using piezoelectric nano powder and commercial paint for railroad vehicles, and the application of impact monitoring to railroad vehicles was analyzed. The process was simplified because the use of commercial paint eliminated the need to apply an additional layer of functionalized paint. Furthermore, the fact that the paint can be evenly sprayed on a large surface made it suitable for use on large and intricate objects such as a railroad vehicle bogie. Because railroad vehicles are exposed to thermal stress for a long period of time, a thermal fatigue test was conducted in order to figure out the stability of the polymer-based material, which is relatively vulnerable to temperature variations. The test results were used to analyze the impact sensitivity of the piezoelectric paint sensor. For the analysis, a full-size mock-up of the railroad vehicle bogie and an impact monitoring system with piezoelectric paint sensor were implemented in order to visualize the impact signals from differently shaped objects with large surfaces.

Radiosity from Individual Urban Landscape Elements Measured Using a Modified Low-Cost Temperature Sensor

Loss of green space in our suburban environment is contributing to increased urban heat. The material properties of surface treatments or landscape elements (LEs) are a determining factor in the amount, timing, and type of radiation present in the local environment. Landscape designers can use this information to better design for urban heat management, as emitted and reflected radiation (radiosity) from LEs can affect pedestrians via heat stress and glare and affect energy usage in buildings and houses if the landscape sky view factor is low. Low-cost black painted iButton temperature sensors were successfully used as radiometers to concurrently measure the daytime radiosity from 19 LEs samples located on an oval in the warm temperate climate of Perth, (Australia). Normalisation against gloss white paint on polystyrene removed the effect of varying weather conditions. Each LE had the same normalised average radiosity (DRav) between seasons (within ±5%), meaning the relative radiosity of new LEs can be measured on any day. White and lighter coloured LEs had the highest DRav and would have the most detrimental effect on nearby objects. Plants and moist LEs had the least DRav and would be most beneficial for managing local daytime urban heat. Measuring relative radiosity with iButtons presents a new way to examine the effect of LEs on the urban environment.

Impact paint sensor based on polymer/multi-dimension carbon nano isotopes composites

We presented a novel impact paint sensor made of piezoresistive nano-carbon composites and studied its characteristics. The paint sensors were fabricated with multi-walled carbon nanotube (MWCNT), exfoliated graphite nano-platelets (xGnP), and a hybrid type of the two nano-carbon fillers and were sprayed onto a carbon fiber-reinforced plastic panel for lab testing. In ball drop impact test, the MWCNT-xGnP-based hybrid sensor showed the best characteristics in impact energy sensing within the range 0.07–1.0 J. We also studied the piezoresistive mechanism due to dimensional variations of nano carbon isotopes for sensor design. Piezorestivity of nano-carbon sensor was significantly dominated the electrical contact variation of the electrical fillers in a matrix. This study is expected to provide a feasibility test for designing impact paint sensors with optimized sensitivity for a composite structural health monitoring.

Smart nano composite paint sensors for infrared detecting and energy harvesting

Smart nano composite paint sensors for infrared detecting and energy harvesting

Piezoelectric characteristics of PNN-PZT/Epoxy paint sensor according to the poling conditions

This paper deals with piezoelectric characteristics according to the poling condition in order to improve the disadvantage of conventional poling treatment and find optimal poling condition for the paint sensor. The paint sensor is composed with PNN-PZT (Pb(Nb,Ni)O3-Pb(Zr,Ti)O3) powder and epoxy resin by 1:1wt percent (12.2:87.8vol fraction) in order to reduce the cost and weight. The specimen was made up by using steel mold to get a uniform size, and the dimensions of the paint sensor are 20×10×1.0mm3. The poling treatment has been carried out under controlled conditions of the electric field and the poling time, while the poling temperature has been fixed at the room temperature. The output voltage from the paint sensor and the force from the impact hammer were measured by DAQ device (NI, PXI-6259) in order to measure the piezoelectric sensitivity, when the impact hammer hits the paint sensor by using impact device. The piezoelectric sensitivity defined comparing a paint sensor output voltage with impact force and piezoelectric properties by suggested equation for the paint sensor. The analysis of variance was performed to check the main effect and interaction effect on the sensitivity. In conclusion, the poling time affects the sensitivity more than poling electric field. The optimal poling condition of the paint sensor was obtained that the poling time is 30min, and the electric field is 4kV/mm at room temperature in the air.

CNT network modeling and simulation of the electrical properties of CNT/PNN-PZT/epoxy paint sensor

In this study, the electrical properties of Carbon nanotubes (CNT)/PNN-PZT/epoxy paint sensor, a kind of piezoelectric composites, were simulated to explain the effect of the dispersion state of Multiwalled CNT (MWCNT) in the paint sensor on sensor characteristics. The conductivity of the CNT/PNN-PZT/epoxy paint was calculated by the 3D resistor network simulation in consideration of the length, dispersion state, and volume fraction of MWCNT. The electrical property of the paint sensor was predicted efficiently by a simple simulation method. Both the conductivity of the piezoelectric composite and the percolation threshold of MWCNT in the piezoelectric composite were simulated according to the dispersion state of MWCNT in the composite. Finally, the simulation results were compared and verified with experimental data.

압전 페인트 센서를 활용한 충격 모니터링 활용 방안

Abstract The piezoelectric paint sensor is a paint type sensor comprising of an epoxy and piezoelectric powder, which is the main component of a piezoelectric material. This sensor can be easily attached to any type of structure as compared to other sensors because it is viable to directly apply it on structures, as in the case with a typical paint. In this study, the capability of piezoelectric paint sensor for impact detection was evaluated. In Particular, the applications of the piezoelectric paint sensor for railroad vehicles were considered. There have been various cases reported about the damages caused by flying gravel to the under-cover of the railroad vehicle during operation. In order to prevent this, real-time monitoring of the large under-cover surface of the railroad vehicle is unavoidable. Under the assumption of vehicle application, sensor sensitivities were measured after multiple and prolonged exposure to thermal cycle environment (-20~60℃). Sensitivity evaluation of paint sensor under environmental conditions was conducted in an aluminum specimen. In results, despite the small variations in sensitivity, we could confirm the applicability of this paint sensor for impact detection even after a severe environmental exposure test.

분극 시간에 따른 압전 페인트 센서의 압전 특성 연구

본 논문에서는 분극 시간에 따라 압전 페인트 센서의 특성이 어떻게 변하는지 평가하고, 그 결과를 기술하였다. 연구에 사용된 압전 페인트 센서는 유연 압전 재료인 Pb(Ni1/₃Nb<SUB>2/3</SUB>)O₃?Pb(Zr, Ti)O₂(PNN-PZT)와 에폭시 수지를 무게비 1:1로 혼합하여 제작하였다. 센서 시편은 몰드를 사용하여 40×10×1㎣ 크기로 제작하였고, 윗면과 아랫면에 실버 페이스트를 사용하여 전극을 제작하였다. 분극작업 시 온도는 상온으로, 분극 전계는 4kV/mm 고정한 상태에서 분극 시간을 달리함으로써 분극조건을 달리하였다. 분극 특성은 충격 망치를 이용하여 충격을 시편에 가했을 때 충격 망치에서 측정되는 힘과 압전 페인트 센서에서 출력되는 전압을 비교하여 살펴보았다. 그 결과, 상온에서 분극전계가 4kV/mm인 경우, 30분 정도 분극 처리를 한 경우 가장 최적의 분극 조건임을 확인하였다.

분극 전계에 따른 압전 페인트 센서 감도 측정

ABSTRACT: In this study, the experimental study has been performed by varying the polarization of the electric fieldand impact force to check the piezoelectric characteristics of piezoelectric paint sensor. Piezoelectric paint sensor usedin this study is composed of epoxy resin with a hardener and PNN-PZT powder in 1:1 weight ratio. The dimensionsof the paint sensor specimen are 40 × 40 × 1 mm 3 and regular specimens were made using a mold. The voids areremoved from the specimen in the vacuum desiccator. Both upper side and bottom side of the paint sensor werecoated with silver paste for making an electrode and then dried at room temperature for a day. The poling treatmenthas been carried out under controlled conditions of the electric field in order to check the effect of piezoelectricsensitivities, while the poling temperature was fixed at room temperature and the poling time was set to 30 min. Thepiezoelectric sensitivities have been measured by comparing output voltage from paint sensor with output force fromimpact hammer when the impact hammer hits the paint sensor. In result, the effect of the electric field has beenevaluated for the sensitivity and describe the result.초록

Vibration and impact monitoring of a composite-wing model using piezoelectric paint

This study investigates a piezoelectric paint sensor for large area sensing applications, and its sensing characteristics under dynamic loading conditions such as impact and vibration. The piezoelectric paint is composed of the Pb(Nb,Ni)O3-Pb(Zr,Ti)O3 (PNN–PZT) powder and epoxy resin. The PNN–PZT is a kind of soft piezoelectric material that offers many advantages such as high piezoelectric properties, easy poling, and so on. The PNN–PZT/epoxy paint sensor can be easily applied to various engineering structures, even to those having a complex geometry or curved shapes because of its flexibility. In this study, the PNN–PZT/epoxy paint was coated on a composite-wing model. One electrode was made on the upper surface of the piezoelectric paint, while the graphite/epoxy composite structure itself was used as the other electrode. Then poling was conducted at room temperature (20 °C) under a 4 kV/mm electric field for 10 min. When the composite-wing model was subjected to free-vibration, its vibration response was monitored by measuring the output voltage of the piezoelectric paint sensor; when the composite-wing model was impacted by an impact hammer, its impact signal was also measured by the piezoelectric paint sensor. The vibration and impact test results showed that the PNN–PZT/epoxy paint sensor captured the dynamic responses of the composite-wing structure very well. We believe that the piezoelectric paint sensor can be useful in many engineering applications such as real-time vibration and impact monitoring, damage detection, nondestructive structural health monitoring, and so on.

Smart paint sensor for monitoring structural vibrations

A class of smart paint sensors is proposed for monitoring the structural vibration of beams. The sensor is manufactured from an epoxy resin which is mixed with carbon black nano-particles to make it electrically conducting and sensitive to mechanical vibrations. A comprehensive theoretical and experimental investigation is presented to understand the underlying phenomena governing the operation of this class of paint sensors and evaluate its performance characteristics. A theoretical model is presented to model the electromechanical behavior of the sensor system using molecular theory. The model is integrated with an amplifier circuit in order to predict the current and voltage developed by the paint sensor when subjected to loading. Furthermore, the sensor/amplifier circuit models are coupled with a finite element model of a base beam to which the sensor is bonded. The resulting multi-field model is utilized to predict the behavior of both the sensor and the beam when subjected to a wide variety of vibration excitations. The predictions of the multi-field finite element model are validated experimentally and the behavior of the sensor is evaluated both in the time and the frequency domains. The performance of the sensor is compared with the performance of conventional strain gages to emphasize its potential and merits. The presented techniques are currently being extended to sensors that can monitor the vibration and structural power flow of two-dimensional structures.

Sensitivity analysis of piezoelectric paint sensors made up of PZT ceramic powder and water-based acrylic polymer

A strain sensor based on piezoelectric paint film has been designed to be used in structural vibration monitoring applications. The piezoelectric paint film can be considered as a piezoelectric composite constituted by two phases: lead zirconate titanate (PZT) ceramic powder (active phase) homogeneously distributed in a water-based acrylic polymer (passive phase). Two electrodes placed to both sides of the film are required to measure the electric charge generated by the sensor. Because PZT is a ferroelectric material, the film must be polarized with a high electric field across the electrodes prior to use. The sensor sensitivity, defined in this work as the electric displacement relative to the biaxial strain of the substrate surface in which the sensor is attached, has been analyzed as a function of various parameters: the electric field applied to polarize the sensor; the time during which the electric field is applied; the film thickness; the electrode area; and the concentration of PZT by weight. From the analysis of the experimental results a mathematical model has been proposed which defines the sensor sensitivity as a function of the previously mentioned parameters.

Dynamic characterization of piezoelectric paint sensors under biaxial strain

A piezoelectric paint film has been designed to be used as a strain sensor. The composite is a suspension of milled lead zirconate titanate (PZT) ceramic powder in a polymer binder (water-based acrylic). The sensitivity of the sensor was estimated as the electric displacement (electric charge per electrode area) generated by the sensor relative to the strain experienced by the substrate surface, under the hypothesis that the electric charge generated is proportional to the sum of the principal strains. The piezoelectric constant d 31 (conventionally used to characterize piezoelectric sensor materials for structural vibration measurement) has also been obtained. The sensor linearity has been demonstrated over a strain range of ±200 μɛ and the sensor sensitivity is shown to be flat to within ±2 dB over a frequency range of 5–500 Hz, ranges typically required for structural vibration monitoring applications.

A Constitutive Model for Piezoelectric Paint with Mixed Connectivity

This article presents a constitutive model for piezoelectric paint that addresses its special characteristics such as mixed connectivity and air void content. Piezoelectric paint is a composite piezoelectric material that is comprised of tiny piezoelectric particles randomly dispersed within a polymer matrix phase. The feasibility of using piezoelectric paint for ultrasonic sensing such as acoustic emission sensor has been demonstrated in the literature. With an emphasis on sensor application, a constitutive model that considers the special characteristics of piezoelectric paint such as mixed connectivity and air void content is formulated in a semi-empirical approach. The focus of this study is given to piezoelectric paints with a piezoelectric ceramic volume fraction ranging from 35% to 60%, for which some of the active particles form 1-3 connectivity, leading to higher piezoelectric activity than previous models for piezoelectric 0-3 composites predict. Percolation theory is used to empirically model the rapid increase of piezoelectric activity after a threshold level of piezoelectric ceramic particle volume fraction is exceeded in the piezoelectric paint. Such a constitutive model is very useful to sensor design since the insight gained from a parametric study of piezoelectric paint properties will provide input to optimizing paint formulation for a particular sensor design. The effect of piezoelectric particle volume fraction on the electromechanical properties of piezoelectric paint is first examined and is followed by a discussion of the air void content and polarization effects. The proposed percolation-based mixed connectivity model for piezoelectric paint sensor has been calibrated with experimental data.

Spatial portability of numerical models of leaf wetness duration based on empirical approaches

Leaf wetness duration (LWD) models based on empirical approaches offer practical advantages over physically based models in agricultural applications, but their spatial portability is questionable because they may be biased to the climatic conditions under which they were developed. In our study, spatial portability of three LWD models with empirical characteristics – a RH threshold model, a decision tree model with wind speed correction, and a fuzzy logic model – was evaluated using weather data collected in Brazil, Canada, Costa Rica, Italy and the USA. The fuzzy logic model was more accurate than the other models in estimating LWD measured by painted leaf wetness sensors. The fraction of correct estimates for the fuzzy logic model was greater (0.87) than for the other models (0.85–0.86) across 28 sites where painted sensors were installed, and the degree of agreement k statistic between the model and painted sensors was greater for the fuzzy logic model (0.71) than that for the other models (0.64–0.66). Values of the k statistic for the fuzzy logic model were also less variable across sites than those of the other models. When model estimates were compared with measurements from unpainted leaf wetness sensors, the fuzzy logic model had less mean absolute error (2.5 h day −1) than other models (2.6–2.7 h day −1) after the model was calibrated for the unpainted sensors. The results suggest that the fuzzy logic model has greater spatial portability than the other models evaluated and merits further validation in comparison with physical models under a wider range of climate conditions.

Preparation of Nano-Sized ZnO Powder by Freeze-Drying

Zinc oxide(ZnO) has been widely applied in the fields of cosmetics, paint, coating and gas sensor. Size down of ZnO is essential for the preparation of sol or film of ZnO in the application. The size and shape of ZnO particles are controlled by varying drying method. The ZnO was prepared by mixing of zinc acetate and sodium hydroxide at 0°C. Then it was freeze dried or 20°C vacuum dried. After washing the residual ions, it was further compared by drying at 20°C vacuum drying or 200 °C oven drying. The ZnO powder was characterized by XRD, Brunauer-Emmet-Teller analysis(BET) and transmission electron microscope(TEM). The ZnO have wurzite structure with ~10 nm particle size when it was prepared by freeze drying and then 20°C vacuum drying after washing the residual ions. On the other hand, without freeze drying, the ZnO particles observed to be aggregated to 200~400 nm with primary particle size of ~20 nm. The smaller size of ZnO particle in freezing drying compared to 20°C vacuum drying may be explained by frozen water preventing the growth of ZnO particles.