Piezoelectric Polymer Film Research Articles

Study of tunable Fabry-Perot filter based on piezoelectric polymer film

Tunable Fabry-Perot filter (FPF) has high practical value in optic communications. Piezoelectric copolymer P(VDF-TrFE) can be used as spacer material in FPF to obtain large tunability in wide range because of its great electrostrictive effect. The filter has been fabricated with the structure of DBR/electrode/spacer/electrode/DBR. The copolymer is partly etched at where the light traverses. The transmittance spectra have been studied. The resonant wavelengths have been modulated by applied voltage. The optical length is measured to be 804 μm, which shrinks under the electric field. The filter exhibits a total optical path-length change of -0757% under an electric field of 140 V. The results indicate that the electrostrictive effect plays a major role.

411 弾性圧電デバイスを用いた海洋エネルギー発電技術に関する研究(新エネルギー(1))

We have developed a way of harvesting electrical energy from the ocean power, e.g. tide, current, wave, breaking wave and vortex, using a flexible piezoelectric device consisting of piezo-electric polymer film (PVDF), silicon and natural rubber. The flexible piezoelectric device (FPED) is a hydro-electric ocean energy converter designed to convert renewable energy harnessed from ocean energy into usable electricity. The basic concept generating electric power using FPED is to utilize fluid structure interaction, e.g. flattering, flapping and periodic bending, caused by ocean energy. The FPED deformed by kinetic energy of the ocean power stores elastic energy and also converts it to the electric energy. We carried out some experiments using wave tank and the water tunnel with a bluff body. We have confirmed the electricity generated by wave, current and vortex using the FPED.

A Technology of Electrical Energy Generated From Ocean Power using Flexible Piezoelectric Device

We have developed a way of harvesting electrical energy from the ocean power, e.g. tide, current, wave, breaking wave and vortex, using a flexible piezoelectric device consisting of piezo-electric polymer film (PVDF), silicon and natural rubber. The flexible piezoelectric device (FPED) is a hydro-electric ocean energy unit designed to convert renewable energy harnessed from ocean energy into usable electricity. The basic concept generating electric power using FPED is to utilize fluid structure interaction, e.g. flattering, flapping and periodic bending, caused by ocean energy. The FPED deformed by kinetic energy of the ocean power stores elastic energy and also converts it to the electric energy. We carried out some experiments using wave tank and the water tunnel with a bluff body. We have confirmed the electricity generated by wave, current and vortex using the FPED.

Study on Wave Power Generator Using Flexible Piezoelectric Device

We have developed a new wave power generator using flexible piezoelectric device (FPED) which is a hydro-electric ocean energy unit designed to convert renewable energy harnessed from ocean energy into usable electricity. In our previous works, the FPED consisting of piezo-electric polymer film (PVDF) is a way of harvesting electrical energy from the ocean power, e.g. tide, current, wave, breaking wave and vortex. The concept of this study is that existing coastal and ocean structures (i.e. a breakwater, submerged obstacle, reef in shallow water and submerged plate in deep water) are utilized as a wave power generator sticking with the FPED to make a safety and disaster prevention. We examined the usefulness and electric performance of the FPED deformed by waves in experiments.

Large magnetoelectric effect from mechanically mediated magnetic field-induced strain effect in Ni–Mn–Ga single crystal and piezoelectric effect in PVDF polymer

Abstract Magnetoelectric (ME) effect is observed in a bilayered composite fabricated by laminating one ferromagnetic shape memory Ni–Mn–Ga single-crystal plate with one piezoelectric PVDF polymer film. The reported ME effect originates from the mechanically mediated magnetic field-induced strain effect in the Ni–Mn–Ga plate and piezoelectric effect in the PVDF film. The induced ME voltage shows a good linear response to the applied ac magnetic field in the field range of 0–5 Oe. A large ME coefficient ( α E ) of 1.24 V/(cm Oe) is obtained at an optimal bias magnetic field of 5.1 kOe due to the reversible reorientation of martensitic twin variants in the Ni–Mn–Ga plate. Based on the combination of pseudo-piezomagnetism in the Ni–Mn–Ga plate and piezoelectricity in the PVDF film, the ME effect in the bilayered composite is predicted and found to agree with the experimental results.

Development of a piezoelectric polymer film sensor for plantar normal and shear stress measurements

We have developed a new sensor prototype for plantar pressure measurements during gait. The mechanical stress at the plantar surface has two components, pressure acting normal to the surface and shear stress acting tangential to the surface. The shear stress can be further divided into anterior–posterior (AP) and medial–lateral (ML) components. The developed sensor simultaneously measures both normal and shear stresses. It utilizes commercial polyvinylidenefluoride (PVDF) material and consists of four separate sensor elements. This paper presents the sensor development and calibration for each force components. A shaker providing dynamic excitation force was used in the calibration. Average sensitivities computed from the results were (12.6 ± 0.8) mV/N for the normal force, (223.9 ± 20.3) mV/N for the AP shear force and (55.2 ± 11.9) mV/N for the ML shear force. A preliminary plantar pressure measurement was also done. The results obtained were promising. However, the sensor developed here is the first prototype. In future, a matrix sensor based on this principle is planned to be constructed.

Piezoelectric oxide semiconductor field effect transistor touch sensing devices

This work presents piezoelectric oxide semiconductor field effect transistor (POSFET) based touch sensing devices. These devices are fabricated by spin coating thin (∼2.5 μm) piezoelectric polymer film directly on to the gate area of metal oxide semiconductor (MOS) transistor. The polymer film is processed in situ and challenging issues such as in situ poling of piezoelectric polymer film, without damaging or altering the characteristics of underlying MOS devices, are successfully dealt with. The POSFET device represents an integral “sensotronic” unit comprising of transducer and the transistor—thereby sensing as well as conditioning (and processing) the touch signal at “same site.”

Ultrasonic imaging using air-coupled P(VDF/TrFE) transducers at 2 MHz

A reflection non-contact ultrasonic microscope system working both in amplitude and phase difference modes at 2 MHz has been developed using an air-coupled concave transducer made of piezoelectric polymer films of poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)]. The transducer is composed of three 95 μm-thick P(VDF/TrFE) films stacked together, each of which is activated electrically in parallel by a driving source. The transducer has a wide aperture angle of 140° and a focal length of 10 mm. The measured two-way transducer insertion loss is 80 dB at 1.83 MHz. Despite 20 dB higher insertion loss than that estimated from Mason’s equivalent circuit, we have obtained clear amplitude acoustic images of a coin with transverse resolution of 150 μm, and clear phase difference acoustic images of the rough surface of a paper currency bill with depth resolution of sub-micrometer. Using two planar transducers of P(VDF/TrFE), we have also successfully measured in through-transmission mode the sound velocity and absorption of a 3 mm-thick silicone-rubber plate. The present study proves that, owing to its low acoustic impedance and flexibility, P(VDF/TrFE) piezoelectric film is very useful for high frequency acoustic imaging in air in the MHz range.

Fabrication and measurement of polypeptide‐based piezoelectric composite polymer film.

A new class of polymer composite piezoelectric materials based on piezoactive biopolymer, poly(‐benzyl,L‐glutamate) (PBLG), and a matrix polymer, poly(methylmethacrylate) (PMMA), is presented. The composite polymer offers the possibility of decoupling the electrical and mechanical properties, therefore improving the overall system efficiency. By simultaneously poling and curing (at ambient conditions) PBLG and methylmethacrylate (MMA) mixture solutions, we fabricated a flexible composite film with a significant portion of the PBLG molecules oriented normal to the film surface. This film exhibited moderate piezoelectricity (d33=20 pC/N), and its mechanical characteristics were similar to those of low molecular weight PMMA. Present samples are about 40 μm thick with tensile strength of 13 MPa and Young’s modules of 450 MPa. The frequency response is ± 3 dB from 0.1 to 7 kHz and at 1 kHz is linear with acceleration more than a 10 dB range.

Piezoelectric polymer films as power converters for human powered electronics

Piezoelectric polymer film material allows for conversion of mechanical energy into electrical energy that can be used for supplying electronic devices. While this method does not allow obtaining large useful power, recent advances in electronic technology, in particular wide availability of submicron low-power CMOS processes, have made feasible the idea of using piezoelectric polymers as power converters for human powered electronics. This concept allows to overcome the necessity of using battery as a power source, which is one of the main obstacles to widespread adoption of wearable computing devices. Of particular interest is harvesting energy from walking, which can be achieved by using piezoelectric polymers. In this paper maximum power has been calculated that can be drawn from walking energy owing to application of the copolymer polyethylene–polypropylene (PE–PP) shoe insole. The amount of electric energy obtained from a PE–PP foil of a thickness of 11 μm for a single step of a duration of 1 s – that is equivalent to a frequency of 1 Hz – amounts to 340 nJ.

Combined two frequency array for optoacoustics and acoustics

A combined transducer for optoacoustics and b‐mode ultrasound has to be built according to the specific requirements of both modalities. In order to combine the two tasks in one transducer, we have designed a probe consisting of a PZT array and a PVDF array in a sandwich assembly. The 20 MHz PZT array is a linear array with 128 elements bearing a 150 μm pitch. It operates as a high resolution transmit and receive array for the visualization of geometrical structures in biological tissue. A thin piezoelectric polymer film (PVDF) that is structured as receiving array is superposed to the PZT array. The PVDF array allows to detect the small optoacoustic pressure transients resulting of laser irradiation of small biological structures. Its acoustic impedance of approximately 4‐4,5 MRayl allows to use it in a double function as optoacoustic receiving array and matching layer for the PZT array. The combined array is driven by a custom made multichannel read‐out system supporting sampling frequencies of 80 MHz and combined imaging with b‐mode and optoacoustics. This combined probe integrates the benefits of a high resolution PZT array and gives access to the specificity of optoacoustic signal generation.

307 圧電材料を用いた曲げ変形センサによる関節角度計測に関する研究

This paper showed that a very thin, flexible bending sensor was able to be composed by laminating a polymer piezoelectric film (PVDF film) and processing the electrode geometry appropriately. Moreover, the angle such as the elbow joints of the human body was measured with a developed sensor. A variety of electrode patterns are molded on the surface of a polymer piezoelectric film accumulated by the laser beam machining. It was experimentally clarified that problem of the bending deformation sensor developed before using PVDF film.

Electromechanical Characterization of a Biosensitive and Electroactive Polymer Membrane

Most piezoelectric biosensors normally use crystals, as in the quartz crystal microbalances or surface acoustic wave devices. A new system is described in which piezoelectric polymer films (made of polyvinylidene fluoride, PVDF, and Immobilon, a porous type of PVDF) are used to produce a mass sensitive oscillatory resonant device. Recent results demonstrated that this system successfully detects the binding between bovine IgG (immunoglobulin G) and anti bovine IgG. In order to improve the performance of the biosensor the electromechanical behaviour of such film-membrane is being studied. Miniaturization is also a desirable trend which will be pursued. Thus reports on the dependence on the electrical, mechanical and biological properties with the size of the film will be presented.

2839 高分子圧電フィルムを用いたひずみ測定 : 自由形状の蒸着電極を付与する方法(S37-4 非破壊評価とモニタリング(4),S37 非破壊評価とモニタリング)

Piezoelectric polymer film has recently been recognized as a monitoring sensor because piezoelectric polymer film generates the high voltage in proportion to the strain. From this point of view, amplifier and power are not required. This research is conducted as follows: the potential in the film surface is measured and analyzed using non-contact electrometer, and the method using the lead wire installed on the film is devised. In addition, films with one side electrode are used for this method. Conductive tape and conductive pastes are also used as the electrode installed to the non-electrode surface. However, this method generates uncertain output voltage. So the method for depositing the electrode of arbitrary shape on non-electrode surface is applied.

Evaluation of piezoelectric PVDF polymers for use in space environments. II. Effects of atomic oxygen and vacuum UV exposure

AbstractThe effects of atomic oxygen (AO) and vacuum UV radiation simulating low Earth orbit conditions on two commercially available piezoelectric polymer films, poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE), have been studied. Surface erosion and pattern development are significant for both polymers. Erosion yields were determined as 2.8 × 10−24 cm3/atom for PVDF and 2.5 × 10−24 cm3/atom for P(VDF‐TrFE). The piezoelectric properties of the residual material of both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF‐TrFE) was observed. A lightly cross‐linked network was formed in the copolymer presumably because of penetrating vacuum ultraviolet (VUV) radiation, while the homopolymer remained uncross‐linked. These differences were attributed to varying degrees of crystallinity and potentially greater absorption, and hence damage, of VUV radiation in P(VDF‐TrFE) compared with PVDF. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2503–2513, 2005

Elasticity Control of Curved Piezoelectric Polymer Films

The control of sound transmission through a curved piezoelectric PVDF film was achieved using a negative capacitance circuit as a feedback system. A laser Doppler vibrometer was used to measure the vibration amplitude of the film. The vibration amplitude decreased to near zero and then increased with the reversed phase with increasing feedback voltage. The transmission of sound through the film was significantly suppressed when the vibration amplitude of the film reached near zero. The effect of the thickness and the radius of curvature of the film were tested. The efficiency of feedback depended on the electromechanical coupling factor of the film and the difference of the loss factor between the capacitances of the film and the circuit.

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.

1465 片面電極付高分子圧電フィルムを用いた一定繰返し負荷によるひずみ分布測定法(S20-5 応力・ひずみ分布計測法(1),S20 実験力学的手法による材料・製品の評価)

1465 片面電極付高分子圧電フィルムを用いた一定繰返し負荷によるひずみ分布測定法(S20-5 応力・ひずみ分布計測法(1),S20 実験力学的手法による材料・製品の評価)

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.

Sound isolation by piezoelectric polymer films connected to negative capacitance circuits

Sound isolation has been achieved using a piezoelectric polymer film connected to a negative capacitance feedback circuit. A curved PVDF film was located in the middle of an acoustic tube and the transmission loss of sound through the film was determined in the audio frequency range. At any chosen frequency, the complete isolation of sound was achieved by adjusting the feedback, i.e. the complex capacitance of the circuit was matched precisely to that of the film.