Piezoelectric Polymer Thin Films Research Articles

Thin film formation of PEDOT conductive polymer and PVDF piezoelectric polymer by dip‐coating method assuming application to flexible power generation element

AbstractPoly(3,4‐ethylenedioxythiophene) (PEDOT) conductive polymer and polyvinylidene difluoride (PVDF) piezoelectric polymer thin films were formed by dip‐coating method. The relationship between drawing speed and film thickness was experimentally investigated. Dip‐coated PEDOT and PVDF thin films were characterized and confirmed that both had surely worked as electrode and piezoelectric film of a flexible power generation element, respectively. Using dip‐coating method, these thin films were successfully formed on 3D surface of a bellows shaped spring made of silicone rubber.

Piezoelectric polymer thin films with architected cuts

Abstract

Film formation and characterisation of PVDF piezoelectric polymer thin film by spray coating and its application to helical spring

Poly(vinylidene difluoride) (PVDF) thin film was formed by spray coating method. This method is suitable for fabricating a uniform thin film on a three-dimensional (3D) surface, even if it is complicatedly curved. PVDF is compatible with spray coating because it can be dissolved in an organic solvent. In previous study, we formed PVDF film by bar-coating method, which can deposit PVDF onto substrate by expanding it using a roller bar. However, this method limits coating targets to only flat substrates. In this study, spray coating was carried out to form PVDF film on a 3D surface. After coating, mechanical and piezoelectric properties of PVDF film were characterised. As a result, good mechanical and piezoelectric properties were confirmed. Power-generating element was fabricated using PVDF thin film spray-coated on a 3D helical spring and output voltage was obtained by compressing it.

Reconstrucción de Imágenes Optoacústicas: Efecto de los Sensores Piezoeléctricos de Banda Ancha

La obtención de imágenes optoacústicas es una técnica híbrida con una rápida evolución dentro del área de imágenes biomédicas. Ésta se beneficia tanto del rico y versátil contraste óptico como de la alta resolución espacial asociada con la naturaleza de baja dispersión de propagación de las ondas ultrasónicas. Su aplicación plantea una serie de difíciles problemas que exigen ulteriores desarrollos. Uno de ellos, el objetivo de este trabajo, es analizar cómo afecta a los algoritmos de reconstrucción de imágenes optoacústicas el uso de sensores no ideales (reales) de banda ancha. En particular, como aporte original, se estudia el caso de los sensores ultrasónicos extensos basados en películas delgadas de polímeros piezoeléctricos. Para lograr esto, se implementó un algoritmo de retroproyección temporal para detectores lineales. Luego, usando un modelo paramétrico para este tipo de sensores, se estudió la influencia del uso de un dispositivo real sobre la eficiencia del susodicho algoritmo.

Caracterización de Líquidos por Técnica Fotoacústica: Estudio de Sensores Piezoeléctricos de Banda Ancha

En este trabajo se presenta el estudio sobre tres sensores para sistemas fotoacústicos usados en caracterización de líquidos basados en películas delgadas de polímero piezoléctrico. Su desempeñoo fue comparado llevando a cabo mediciones sobre líquidos de características bien conocidas. A partir de los datos medidos se determinó la sensibilidad, el nivel de ruido y el límite de cuantificación de cada uno de los sensores. Aquel con las mejores características fue utilizado en la determinación de la eficiencia cuántica de los colorantes Rodamina 6G y Rodamina B. Los valores medidos concuerdan muy bien con los reportados por otros autores.

Evolution of electromechanical and morphological properties of piezoelectric thin films with thermomechanical processing

Piezoelectric polymers (PVDF and its co-polymers) in film and nanofiber forms are increasingly used for sensing, actuation and energy harvesting. Given the semi-crystalline structure of these polymers, their electromechanical coupling behavior changes with thermomechanical processing. This article reports on the evolution of the mechanical properties, piezoelectric properties and morphology of P(VDF-TrFE) poly[(vinylidenefluoride)-co-trifluoroethylene] piezoelectric polymer thin films fabricated by spin-coating during thermal annealing and drawing, studied via tensile test, polarized optical microscopy, X-ray diffraction, polarized FTIR, and piezoresponse force microscopy (PFM). The results show that annealing and drawing process result in ∼10 and 13 folds improvement in the elastic modulus and strength of the films, respectively. In addition, the piezoelectric constant and electromechanical coupling improves by 30% and more than 17 times, respectively. These changes are accompanied by 65% increase in the percentage of the crystallinity of the semi-crystalline piezoelectric films, compared to the as-fabricated films.

Reducing the capacitance of piezoelectric film sensors

We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series. In this way, the total capacitance is reduced by a factor 1/N(2), whereas the mechanical response and the active area of the sensor are not modified. We show the construction details for a two-section sensor, together with the impedance spectroscopy and impulse response experimental results that validate the design.

Electromechanical characterization of piezoelectric polymer thin films in a broad frequency range

Piezoelectric materials are usually characterized using resonant methods. However, piezoelectric polymers are used in broadband devices, thus requiring characterization over a wide range of frequencies. In this work, we present a non-resonant method for the broadband electromechanical characterization of piezoelectric polymer thin films. The procedure is based on measuring the complex capacitance of a sample of known geometry under three conditions: free, blocked and immersed in a fluid of known acoustic properties. The behaviour of the sample under study is modelled as a one-dimensional transducer and treated as a two-port network that relates the measurable electrical and mechanical variables. Also, the sample is considered as a free-space radiator when immersed in a fluid. The method determines the intensive and the equivalent circuit parameters of piezoelectric polymer films, allowing the characterization of elastic and electrical properties in a broad frequency range.In order to test the method, we performed isothermal capacitance measurements on a sample of poly(vinylidene fluoride) at a temperature of 298 K. The sample was measured along the direction of the poling field and in the frequency range from 10 Hz to 10 MHz. The results given by the method agree with those reported by other authors.

6PM2-D-4 圧電高分子材料を用いた微小領域内キャビテーション検出センサ(6PM2-D OS7 スマート・インテリジェント材料・デバイス)

In this research, a micro sensor which can detect cavitation in a microchannel has been fabricated by using piezoelectric polymer thin film. P(VDF/TrFE) was used as the sensor material. We have applied integration by using the photolithography process to miniaturize sensors. We have succeeded in fabricating the micro-sensor whose thickness is 158μm. We have also succeeded in receiving waveform in the high frequency range. Thus the sensor would detect cavitation by using frequency analysis of bubbles collapse sound.

Piezoelectric Materials and Devices for Wind Energy Harvesting

AbstractWe present materials development in fabricating thin film devices for the conversion of wind energy as a sustainable energy source. We demonstrate the feasibility of piezoelectric polymer thin film devices to harvest wind energy in a miniature wind tunnel. Using an example of prototype device based on polyvinylidene fluoride (PVDF) thin film devices, we are able to obtain electrical power from the wind’s energy through the mechanical deformation of PVDF, such as that obtained from the films flapping in the wind. We have obtained a preliminary result of 1 mW power (at 15 mph wind) with a single layer of PVDF of 4 x 2 inches and 50 μm in thickness sandwiched between two thin gold electrode films. Additionally, the fracturing of metallic electrodes over time from the induced strain of this application lead to the significance of examining carbon nanotubes as compliant electrodes offering better mechanical properties while maintaining necessary electrical properties.

Residual stress in piezoelectric poly(vinylidene-fluoride-co-trifluoroethylene) thin films deposited on silicon substrates

The residual stress and its evolution with time in poly(vinylidene-fluoride-co-trifluoroethylene) (P(VDF-TrFE) (72/28)) piezoelectric polymer thin films deposited on silicon wafers were investigated using the wafer curvature method. Double-side polished silicon wafers with minimized initial wafer warpage were used to replace single-side polished silicon wafers to obtain significantly improved reliability for the measurement of the low residual stress in the P(VDF-TrFE) polymer thin films. Our measurement results showed that all the P(VDF-TrFE) films possessed a tensile residual stress, and the residual stress slowly decreased with time. Our analysis further indicates that the tensile stress could arise from the thermal mismatch between the P(VDF-TrFE) film and the silicon substrate. Besides possible viscoelastic creep mechanism in thermoplastic P(VDF-TrFE) films, microcracks with widths in the range of tens of nanometers appeared to release the tensile residual stress.

Strain Distribution Measurements Using Piezoelectric Polymer Film Under the Constant Amplitude Load (Strain Formulas of Strain Gauge Models and Examples of Experiment)

The authors deduced strain analysis formulas of strain gauge models and attempted to fabricate strain gauges experimentally using a piezoelectric polymer film in this study. Constant cyclic load tests were carried out using semicircular-holed notched test specimens and center-circular-holed plate. Strains Sx, and Sy are analyzed using the deduced strain formulas. As a result, the following conclusions are drawn. (1) As a result of analyzing the strain using piezoelectric polymer thin film strain gauges, it was shown that the strain analysis method used in this study is effective and the trial strain gauges can he used as an effective tool in an experiment. (2) The piezoelectric polymer film exhibits load frequency dependence. This dependence is a problem in strain measurements. Thus, the authors devised a method of improving this dependence.

908 圧電高分子フィルムを用いたひずみ測定法 : ひずみゲージモデルの解析と実測例

The piezoelectric polymer film (PVDF) of the marketing was cut down in the rectangle, and the strain gage model was produced experimentally. it is called the piezoelectric polymer thin film strain gage. The strain analysis style was deduced from the piezoelectric polymer thin film strain gage model of the rectangle. Using produced piezoelectric polymer thin film strain gage, the experiment was carried out actually. The test pieces used band plate with (1) center circular hole and (2) edge circular hole notch board. Both strain distributions were measured, and the comparison examination was carried out by the combined use of strain gage.

403 圧電高分子フィルムを用いたひずみ測定 : ひずみゲージモデルの解析式と測定

The piezoelectric polymer film (PVDF) of the marketing was cut down in the rectangle, and the strain gage model was produced experimentally. it is called the piezoelectric polymer thin film strain gage. The strain analysis style was deduced from the piezoelectric polymer thin film strain gage model of the rectangle. Using produced piezoelectric polymer thin film strain gage, the experiment was carried out actually. The test pieces used band plate with (1) center circular hole and (2) edge circular hole notch board. Both strain distributions were measured and the comparison examination was carried out by the combined use of strain gage.