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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A new super-multilayer alternating laminated film in the shape of a rectangle with round corners has been developed. The super-multilayer film, which comprised piezoelectric poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) films, was wound with the number of turns on the order of from 100 to 1000 to form piezoelectric rolls. These piezoelectric rolls could generate an induced voltage of more than 95% of the initial voltage for over 10 s when a constant load was applied. The desired duration and magnitude of the piezoelectric response voltage were realized by adjusting the number of turns of the piezoelectric rolls. Similarly to many other conventional piezoelectrics, the piezoelectric rolls enable instantaneous load-dependent voltage generation and attenuation. The piezoelectric rolls are also lighter than conventional piezoelectric ceramics and can be used as a novel pressure sensor. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.10PG03

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We report the potential of a system that enables the monitoring of complex human movements via new smart fabrics based on a piezoelectric poly-L-lactic acid (PLLA) fabric that have the function of sensing complex human motion. In particular, piezoelectric PLLA fabrics with plain, twill, and satin weaves were produced by Teijin Limited, Japan, a joint research company. First, a smart fabric was developed that consisted of pieces of the piezoelectric PLLA fabric with satin, plain, and twill weaves joined in the horizontal direction. The smart fabric, designed to accurately detect the twisting, bending, and elongation of the smart fabric itself was fabricated using a technique for sewing Japanese kimonos. Finally, we developed a prototype system that allows simple human motion to be detected through the motion sensing of clothes capable of being worn on the joints, such as the elbows, shoulders, knees, and waist, obtained by sewing together pieces of the smart fabric. This motion was linked with that of a humanoid robot.

DOI： 10.1080/00150193.2017.1360107

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We designed a new soft piezoelectric polymer actuator with a multilayer structure using the environmentally friendly polymer poly(lactic acid) (PLA). PLA is a chiral polymer having two isomers. One is poly(L-lactide) (PLLA) and the other is poly(D-lactide) (PDLA). PLLA and PDLA exhibit piezoelectric constants with opposite signs owing to their chirality. On the basis of their piezoelectric characteristics, we were able to realize a PDLA and PLLA multilayer film (PDLA/PLLA multilayer) with a simple structure. The PDLA/PLLA multilayer film of centimeter-order size exhibited a large piezoelectric resonance and its piezoelectric performance was equivalent to that of a practical piezoelectric ceramic. In this paper, as a first step toward realizing a new film actuator using the PDLA/PLLA multilayer film, we introduce the piezoelectric characteristics of a PLLA film and the concept of an actuation system using a PLLA film. Next, the fabrication process of the PDLA/PLLA multilayer film and its piezoelectric characteristics are summarized. Finally, typical examples of developed piezoelectric polymer actuation systems using a PDLA/PLLA multilayer film are described to demonstrate the potential application of piezoelectric polymer actuation systems. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.04EA07

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We have developed a piezoelectric fabric for sensing applied stress and strain using piezoelectric poly-l-lactic acid (PLLA) fibers, and tailored smart clothing having the function of sensing complex human motion using the piezoelectric PLLA fabric. To provide a high-quality PLLA fabric with large piezoelectricity, simultaneously satisfying the characteristics of softness, stretchability, and wearability, we first attempted the to improve the balance of the physical properties of PLLA fibers. We investigated the use of an acrylic copolymer as a plastic additive for improving the piezoelectric and mechanical properties of PLLA fibers, since the acrylic copolymer has extremely high dispersibility and compatibility, and the optimized furthermore the PLLA fiber fabrication conditions to improve the physical properties. To realize a piezoelectric fabric with the ability of sensing complex human motion, plain, twill, and satin weaves with improved the piezoelectricity, softness, stretchability, and wearability were produced using the PLLA fibers by Teijin Limited, Japan, a joint research company. Moreover, we developed a prototype system that allows human movement, detected through the motion sensing of smart clothing obtained by sewing together pieces of piezoelectric fabric, to be linked with that of a humanoid robot. At present, simple procedures such as bending of the arms and twisting of the wrists can be replicated by the humanoid robot but not complex movements of the arms.

DOI： 10.1080/00150193.2016.1171982

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Through three-dimensional (3D) printing, we attempted to fabricate 3D solid objects with piezoelectricity. By optimizing the conditions of 3D printing, we realized the fabrication of a piezoelectric object by 3D printing. In fact, we could produce a poly(L-lactide) (PLLA) object similar to a smart phone case fabricated by 3D printing, the molded body of which has button sensors at the desired sites by exploiting the piezoelectric properties of PLLA. Finally, we confirmed that the PLLA object behaved as a fully functional sensor. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.10NF01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Optically active crystalline polymers have shear piezoelectricity owing to their asymmetric crystal structure. In this study, to explore a novel shear piezoelectric polymer, we have focused on an imide ring structure and synthesized optically active polysuccinimides (PSIs), the minimum structure of optically active polyimides. As a result, optically active PSIs were obtained, and we observed that oriented optically active PSI films show shear piezoelectricity. Furthermore, both optical purity and molecular weight are significant factors in piezoelectric performance. This is the first report of the shear piezoelectricity of optically active polyimides, and we identify herein a novel category of a shear piezoelectric polymer. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.10NF02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We developed a new wearable wristband-type piezo-sensor for detecting the pressure signals from the heartbeat. A piezoelectric porous electret made from electro-spun poly(tetrafluoroethylene) (PTFE) was used as the piezo-sensor material. This lightweight and flexibile porous PTFE electret exhibited high and stable piezoelectricity, enabling the realization of a piezo-sensor in a new wearable wristband-type instrument. Using the instrument, we observed a signal with detection accuracy equal to that of an electrocardiogram.

DOI： 10.1109/TDEI.2014.004851

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Toward sensing the complicated motion of the human body, we have developed a new soft and flexible fiber sensor assembled from piezoelectric poly-L-lactic acid (PLLA) fibers (PLLA fiber sensor). As an early stage of this study, we attempted to detect the pulse rate and observe the motion of a human arm using the PLLA fiber sensor. First, we prepared left-hand and right-hand helical torsion coils (PLLA fiber left-hand and right-hand coils), which were formed by drawing a PLLA fiber with a drawing ratio of ten. As a result, we found that the pulse rate could be measured with extremely high accuracy by the PLLA fiber sensor. At the same time, we were able to detect the rotation of the forearm and upper arm using PLLA fiber sensors.

DOI： 10.1080/00150193.2015.1012410

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Recently, the application of uniaxially stretched poly(L-lactic acid) (PLLA) films to speakers, actuators, and pressure sensors has been attempted, taking advantage of their piezoelectric performance. However, the shear piezoelectric constant d(14) of uniaxially stretched PLLA film is conventionally 6-10 pC N-1. To realize a high sensitivity of pressure sensors, compact speakers, and actuators, and a low driving voltage, further improvement of the piezoelectric performance is desired. In this study, we carried out solid-state extrusion (SSE) to stretch and orient poly(D-lactic acid) (PDLA) and verified its effects on piezoelectric performance. By SSE, we were able to improve the mechanical strength and elastic modulus of PDLA samples. Furthermore, the d(14) of the samples was significantly increased to approximately 20 pC N-1. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.09PC02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

It has been reported that poly(beta-phenethyl L-aspartate) (PPLA) exhibits irreversible inversion from right-handed to left-handed helixes in a solid state at 130-140 degrees C from the results of circular dichroism measurement and X-ray diffraction. On the other hand, it is well known that semicrystalline chiral polymers show shear piezoelectricity due to their asymmetric crystal structure. The results of macroscopic shear piezoelectric measurement include information on macroscopic and microscopic properties due to the helix structure of the chain molecules. However, in general, no direct correspondence has been reported between the macroscopic piezoelectric properties and crystal characteristics because of the existence of a unique complex high-order structure in polymer films. We measured the temperature dependence of the piezoelectricity of a PPLA film in order to obtain more information concerning the helix inversion process. As a result, the sign inversion of the piezoelectric constant was observed at the temperature at which the helix inversion took place. It was also shown that the macroscopic orientation of the crystalline structure was maintained in the PPLA film after the sign inversion, even though molecular motion such as the segmental motion and side-chain motion of PPLA molecules was activated. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.09PC01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We developed a piezoelectric polymer film that was an electret using a porous poly(tetrafluoroethylene) (p-PTFE) film with high piezoelectricity and high heat resistance. First, we found that the p-PTFE electret had a piezoelectric constant d(33) of 100 pC/N after the optimization of its pore size. This value was about five times as large as that of poly(vinylidene fluoride) (PVDF) and was retained up to a temperature of as high as 120 degrees C. Then a new device using the laminated film with perfluoroalkoxy (PFA) laminated on one side of the p-PTFE electret was developed for the demonstration of pressure sensing. A new flexible device with a large area was realized. Then, for the demonstration of pressure sensing, a plastic touch pen for a touch panel was traced on the surface of the device at a constant speed of 80 mm/s under a compressive load of 0.05 N. The results confirmed that the device exhibited superior sensing responsiveness. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.09PC04

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We designed a new film actuator, whose driving force is generated by a surface wave, which induces rotational motion. Its performance is similar to that of a rotation motor even though the new film actuator has no complex mechanical parts. To realize the film actuator, we used a poly(l-lactic acid) (PLLA) film with improved piezoelectricity. First, we theoretically investigated the necessary conditions for a surface wave to be generated on the end face of a PLLA film by the fusion of its shear piezoelectricity and resonance, and then experimentally realized this. Using the actuator made using the PLLA film, we demonstrated that the clockwise and counterclockwise rotation of an object placed on the end face of the PLLA film actuator could be freely controlled by changing the frequency of the ac voltage applied to the actuator. © 1986-2012 IEEE.

DOI： 10.1109/TUFFC.2013.2744

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Synthetic piezoelectric polymer films produced from petroleum feedstock have long been used as thin-film sensors and actuators. However, the fossil fuel requirements for synthetic polymer production and carbon dioxide emission from its combustion have raised concern about the environmental impact of its continued use. Eco-friendly biomass polymers, such as poly(L-lactic acid) (PLLA), are made from plant-based (vegetable starch) plastics and, thus, have a much smaller carbon footprint. Additionally, PLLA does not exhibit pyroelectricity or unnecessary poling. This suggests the usefulness of PLLA films for the human-machine interface (HMI). As an example of a new HMI, we have produced a TV remote control using a PLLA film. The intuitive operation provided by this PLLA device suggests that it is useful for the elderly or handicapped. (c) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.09LD14

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

To realize a new polymer sensor fabricated from a piezoelectric chiral polymer fiber, we attempted to detect the response signal induced by the shear piezoelectricity of the chiral polymer poly(L-lactic acid) (PLLA) under the application of stress and strain, and we confirmed that the piezoelectric response signal was sufficiently large for use as a sensor signal. We then prepared a left-hand helical torsion coil (PLLA fiber left-hand coil), which was formed by drawing a PLLA fiber ten times. It was observed that, when twisted and released suddenly, the coil exhibited a torsion vibration, and we confirmed that the piezoelectric response signal followed the torsion vibration. Next, we prepared a system in which a PLLA fiber coil was linked to a personal computer used for simple image processing. The PLLA fiber left-and right-hand coils were placed on the arm of a subject, and the inward rotation and outward rotation of the forearm and upper arm were measured. Finally, using this system, we were able to visualize the rotation of the forearm and upper arm. (c) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.09LD16

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We designed a new polymer film transducer that can generate a surface acoustic wave. The transducer is fabricated by rolling a piezoelectric poly(l-lactic acid) (PLLA) film into a long thin roll (PLLA film roll transducer). The PLLA film roll transducer induced the rotation of an object placed its the upper end face via the torque caused by the generated surface acoustic wave. Moreover, a noteworthy experimental result is that the clockwise and counterclockwise rotation of the object can be freely controlled by changing the frequency of the ac voltage applied to the PLLA film roll transducer. We emphasize that no special complex mechanical parts were used in this study.

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We designed a new polymer film transducer that can generate a surface acoustic wave. The transducer is fabricated by rolling a piezoelectric poly(l-lactic acid) (PLLA) film into a long thin roll (PLLA film roll transducer). The PLLA film roll transducer induced the rotation of an object placed its the upper end face via the torque caused by the generated surface acoustic wave. Moreover, a noteworthy experimental result is that the clockwise and counterclockwise rotation of the object can be freely controlled by changing the frequency of the ac voltage applied to the PLLA film roll transducer. We emphasize that no special complex mechanical parts were used in this study. © 2012 IEEE.

DOI： 10.1109/ISAF.2012.6297732

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

We realized a multilayer film laminated alternately with poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) films in order to improve the piezoelectric performance of the PLLA film. In the fabrication processes, the thicknesses of PLLA and PDLA films were reduced to improve the effective electric field, and a multilayer composed of more than 100 layers (PDLA/PLLA multilayer film) was realized to improve the piezoelectric performance. In general, a single PLLA film has a piezoelectric constant of about 5 pC/N, and it is difficult to observe the piezoelectric resonance in this film of centimeter-order size using a commercial impedance analyzer because of its small Q-value. In contrast, the PDLA/PLLA multilayer film of centimeter-order size has a piezoelectric performance equivalent to that of the piezoelectric material with a piezoelectric constant of 100 pC/N, and also, the piezoelectric resonance can be observed in this film. On the basis of these results, we confirmed that even an object of 259 g mass is made to vibrate under the piezoelectric resonance vibration of this PDLA/PLLA multilayer film. In other words, necessary quantities for actual work as an actuator could be obtained in the PDLA/PLLA multilayer film. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.50.09ND13

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

To attempt the realization of a highly piezoelectric polymer film, we used an oriented poly(gamma-benzyl-L-glutamate) (PBLG) film that was cast from chloroform solution under the strong magnetic field induced by a generation apparatus using a superconducting magnet. First, the orientation of the PBLG principal chain in the film was observed macroscopically by polarizing microscopy (POM), and it was found that the orientation of the principal chain differed in each region. Then, in order to observe each region, using our original apparatus, the birefringence (retardation) and optical axis were measured at 100 mu m pitch/point-to-point, and a cm-order region with high retardation was found. We then cut off a small piece from this region of the PBLG film and evaluated the shear piezoelectric constant. A large shear piezoelectric constant of 18 pC/N was found in the small piece. Also, the PBLG film was investigated by atomic force microscopy (AFM). We found a characteristic slender structure in the region with a high macroscopic shear piezoelectric constant. Furthermore, the piezoelectric motion due to its shear piezoelectricity in the region was investigated microscopically by piezoresponse force microscopy (PFM), which successfully enabled the direct observation of the piezoelectric displacement due to its shear piezoelectricity in one direction in the entire region with the characteristic slender structure. On the basis of these results, we speculate that the principal chain was highly oriented and crystallized in the region with the characteristic slender structure, resulting in a large shear piezoelectric constant in the region. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.50.09ND02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Ferroelectret films (FFs) were fabricated using porous polyethylene (p-PE) film with various polarities treated by corona discharge. Their piezoelectric constant in the direction perpendicular to their surface was over 100 pC/N Hence, in order to clarify the piezoelectric motion, Piezo-Response Microscope (PRM) measurements and perpendicular elasticity measurements of the ferroelectret p-PE film were carried out. As a result, first, we found that there is a strong correlation between elastic and piezoelectric constants, and second, the areas surrounding the pores shift in one direction following the application of ac voltage, but areas far from the pores cannot move freely. For the mechanism behind expression of the piezoelectric phenomenon, these results indicate that a large decrease in thickness occurs predominantly across the pores upon the application of stress and, as a result, the macroscopic polarization caused by trapped electric charges surrounding pores increases considerably following the change in thickness. Therefore, a large piezoelectric constant is observed in ferroelectret p-PE film.

DOI： 10.1080/00150193.2011.577372

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In order to control the bending motion of poly-L-lactic acid (PLLA) fiber, which is one type of chiral polymer, caused by its shear piezoelectricity upon applying electric field, we simulated the electric field distribution in the PLLA fiber by a finite-element method. As a result, we found that the electric field distribution depends strongly on the distance between the electrodes on the surface of the PLLA fiber. On the basis of the simulation results, we design some electrodes on the surface of the PLLA fiber. When we applied an electric field with a tangential component in the cross section perpendicular to the fiber axis, using one electrode, linear motion could be realized owing to its piezoelectricity. Furthermore, when we added a radial component of the electric field using another electrode, the motion could be changed from linear to elliptical.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Chiral polymers have been known to exhibit small shear piezoelectricity for about fifty years. However, recently, we reported that poly(L-lactic acid) treated with supercritical carbon dioxide (sc-PLLA), which is a type of chiral polymer, exhibits much higher shear piezoelectricity than other chiral polymers. On the other hand, we found an important difference between motion due to shear piezoelectricity and that due to tensile piezoelectricity in piezoelectric materials through computer simulations. On the basis of these results, we fabricated a new type of electrically controlled tweezers constructed from a pair of sc-PLLA sheets with shear piezoelectricity. In general, when conventional tweezers open to the left and right, the trajectory of their motion becomes fanlike at the center of the connection (one end of the tweezers). In the new tweezers, the two small sheets making up the tweezers open parallel to each other, without the motion of parts near the connection. Moreover, a prototype 'finger' system using sc-PLLA sheets to realize complex motion in which the finger curled upon stretching of the sc-PLLA sheets was manufactured as a trial device. Using the prototype finger system, we demonstrated the firm grasping of a sample, but the sample could not be removed from a vessel. Thus, sc-PLLA increases the likelihood of realizing a device with highly operational pick-up in a very small region by using the shear piezoelectricity of a chiral polymer. (C) 2010 Society of Chemical Industry

DOI： 10.1002/pi.2758

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The piezoelectricity of a film of the eco-material poly(L-Lactic acid) (PLLA) with high transparency and flexibility has been noted for its possibility of application to new types of devices used in mobile equipment. However, for its application, there are many difficult problems to be solved, because the PLLA film has poor thermal stability. To change the high-order structure of the PLLA film, thus realizing an improvement in the temperature dependence of its piezoelectricity, a composite film with a stereocomplex crystal (SC) formed from PLLA and poly(D-lactide acid) (PDLA) molecules was fabricated. As a result, we obtained a composite film with a stable piezoelectric temperature dependence compared with a pure PLLA film. To analyze its piezoelectric temperature dependence, we first observed the high-order structure of the composite film using a polarized microscope (POM). However, we did not find any difference between the high-order structures of the composite film and the pure PLLA film. In contrast, from observation by atomic force microscopy (AFM), it was found that the grain structure in the composite film became more homogeneous than that in the pure PLLA film. These experimental results indicate that, by changing the high-order structure through a compound with SC, the external stress always has a constant effect over a wide temperature range and, as a result, the induced polarization is constant in the composite film. Thus, the composite film shows excellent thermal stability of piezoelectricity compared with the pure PLLA film. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.09MC11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The piezoelectric constant of a poly(L-lactic acid) (PLLA) fiber is larger than that of other piezoelectric polymers. It is well known that it is easier to fabricate large devices with a flexible shape using polymer materials than using inorganic materials. Thus, on the basis of the features of polymer materials, we attempted to fabricate a PLLA actuator for a large macroscale physical object using PLLA fibers. We consider how to bundle PLLA fibers into a tubular-type polymeric actuator (PLLAFTTPA) with electrodes for producing piezoelectric motion under the application of voltage. Then, by thermal welding, a PLLAFTTPA with electrodes on its inner and outer surfaces was manufactured. Finally, we succeeded in producing a PLLAFTTPA with a diameter of 1 cm and a length of 12 cm. We observed that, under the application of an ac voltage of 2 kV, the PLLAFTTPA could be tilted 20 mu m in the fixed direction when the base of the PLLAFTTPA was mounted. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.09MD14

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Poly(L-lactic acid) (PLLA), which is a type of chiral polymer, was subjected to a supercritical CO2 (s-CO2) treatment to change its high-order structure, realizing an improvement in its piezoelectricity. The piezoelectric constant e of the PLLA film treated with s-CO2 (sco2-PLLA) was twofold higher than that of the PLLA film fabricated by the conventional method. From observation by atomic force microscopy (AFM), it was found that, upon treatment with s-CO2, the grain structure of the sco2-PLLA film became homogeneous, in comparison with that in the PLLA film without s-CO2 treatment. Then, we confirmed that, using the sco2-PLLA film, vibration control using a negative-capacitance circuit could be more efficiently carried out than that using the PLLA film without s-CO2 treatment. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.09KE06

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOCIETY APPLIED PHYSICS  

A ferroelectret porous polyethylene (Fp-PE) film with a thickness of 30 mu m and a porosity of 58% was fabricated; its perpendicular piezoelectric constant d(33) was 80 pC/N. In the Fp-PE film observed by atomic force microscopy (AFM), pores with a diameter of about 0.3 mu m were almost homogeneously distributed. Moreover, from piezoresponse force microscopy (PFM), it was found that areas surrounding the pores shift in one direction following the application of ac voltage, but that areas far from the pores cannot move freely. These results indicate that the electrical charges trapped in areas surrounding the pores in the Fp-PE film play an important role in piezoelectricity. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.09KE05

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We studied a novel technique for electrically controlling the piezoelectric motion of the fiber of poly-(L-lactic acid) (PLLA), which is a type of chiral polymer. A PLLA fiber (30 mu m diameter) drawn seven times with a piezoelectric constant of 25 pC/N was prepared. First, it was reported that a bending motion due to the shear piezoelectricity of the PLLA fiber can be basically controlled by applying an electric field. Then, it was found that the targeting piezoelectric actuator that we used to study the tip motion of the free end of PLLA fibers whose other end was fixed, could be moved in a zig-zag pattern on a straight line, and/or along an ellipsoidal orbit, by the application of an electric field.

DOI： 10.1080/00150190902987871

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The electrically controlled piezoelectric motion of a fiber of poly(L-lactic acid) (PLLA), a type of chiral polymer, is invertigated. Laser light was propagted into the PLLA fiber and when the controlling electric field was applied to the fiber, the direction of the outgoing beam from the fiber changed owing to its piezoelectric motion. The change in direction was recorded using two charge coupled device (CCD) video cameras: one faces the tip of the PLLA fiber and the other is placed above the tip of the fiber. First it was realized that the outgoing beam moved in a zigzag manner when we applied the ac voltage with high harmonic waves to the PLLA fiber. Furthermore, when a component parallel to the PLLA fiber axis of the applied electric field was generated, the trajectory of the outgoing beam changed from a straight line to an ellipse.

DOI： 10.1143/JJAP.47.7642

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WILEY-V C H VERLAG GMBH  

Hydroxyapatite (HAp)-polyvinyl alcohol (PVA) nanocomposite film containing Li(+) was designed as a solid polymer electrolyte. A composite was prepared by reacting Ca(OH)(2) with H(3)PO(4) in the presence of PVA which is denatured in order to have the carboxyl group, and a LiN(CF(3)SO(2))(2) was added. HAp particles were commonly formed in the shape of spindles (long axis ca. 80 nm and short axis ca. 25 nm). The obtained nanocomposite film, in which HAp particles were dispersed uniformly, is transparent, flexible and drawable. its ionic conductivity is about 10(-3) S/m at room temperature. This value is very large. This high ionic conductivity is considerable on the basis of the dynamic percolation theory.

DOI： 10.1002/masy.200850803

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

We studied a method of controlling the elastic modulus of lead zirconate titanate (PZT) using the negative-capacitance circuit (NCC). NCCs are of two types: soft NCC that softens the piezoelectric material and hard NCC that hardens the piezoelectric material. In this study, the piezoelectric materials PZT ceramics and poly(L-lactic acid) (PLLA) were prepared. The elastic moduli of these materials markedly differ. By connecting the materials to soft and hard NCCs, the control of the vibrations of PZT ceramics and PLLA was studied. It was found that only the vibration amplitude of PZT ceramics markedly changes with the connection to soft and hard NCCs. In other words, no complex vibration mode of the PZT ceramics, such as torsion, chattering and segmental vibrations, is induced. It was also shown that only the vibration amplitude of PLLA, which is a softer material than PZT ceramics, could be similarly controlled by connection to soft and hard NCCs.

DOI： 10.1143/JJAP.46.7053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

\We studied a method for electrically controlling the bending of a poly(L-lactic acid) (PLLA) fiber. First, we simply evaluated the piezoelectric characteristics of PLLA fibers, which were produced under various conditions, to study bending motion using the measurement system developed here. As a result, a PLLA fiber (drawn seven times, 150 mu m diameter) with a molecular weight of 20,000 showed the largest piezoelectric modulus of 25 pC/N. Then, we found that a PLLA fiber bent with the application of an electric field to the fiber. That is, the bending motion of the PLLA fiber could be controlled. Also, it was demonstrated that the fabrication of an on/off switching system was possible using the bending motion jointly with a logic circuit.

DOI： 10.1143/JJAP.46.71221

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Generally, plastics and plastic films are low in moisture absorption and high in electric insulation. They are inherently easy to be charged with static and can cause a variety of static troubles. We developed a functional packaging material to solve these static problems, by using potassium ionomer. We reported good antistatic performance (e.g. short static decay time, and excellent ash test) of potassium ionomer films in a previous paper. However, a mechanism underlying the antistatic property of potassium ionomer has not yet been fully elucidated. In this study, we measured the space charge distributions of potassium ionomer using the pulsed electro-acoustic method. As a result of the space charge measurements, we found characteristic charge distribution of potassium ionomer film. On the basis of the existence of this characteristic charge distribution, we speculate that the space electric charge distribution of a potassium ionomer film under a direct current electric field shows apparent electric charge movement. Copyright (c) 2006 John Wiley & Sons, Ltd.

DOI： 10.1002/pts.759

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We report a novel technique for controlling the elastic coefficient of piezoelectric lead Zirconate titanate (PZT) by connecting an electric circuit that behaves as a "negative capacitor" (hereafter referred to as negative-capacitance circuit). In this experiment, a PZT ceramic was connected with the negative-capacitance circuit. The attenuation factor in transmission loss from the ratio of the signal obtained using the system with the negative-capacitance circuit to the signal obtained without the negative-capacitance circuit was calculated. The attenuation factor in transmission loss was grater than 10 dB in the frequency range from 1 kHz to 100 kHz.

DOI： 10.1080/00150190701195932

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We studied a novel technique for controlling the elastic coefficient of a piezoelectric lead zirconate titanate (PZT) ceramic by connecting a negative-capacitance circuit that behaves as a "negative capacitor". Thus, we can realize control through a mechanism in which PZT is softened and hardened. On the basis of this technology, we developed a simple experimental system for intercepting elastic waves in the frequency range from 8 kHz to 110 kHz. We determined the attenuation factor in transmission loss of the experimental system, which was more than 10 dB in this frequency range. The maximum attenuation factor in transmission loss was about 60 dB at a frequency of 91 kHz.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

It was shown that it is possible to control the piezoelectric motion of a poly-l-lactic acid (PLLA) fiber by applying d.c. and a.c. voltages as in a piezoelectric actuator. An electrically controlled catheter using piezoelectric PLLA fibers (PLLA fiber catheter) was developed. In the demonstration, it was assumed that thrombosis in blood vessels occurred and removal of the thrombosis from the affected area was attempted using the electrically controlled PLLA fiber catheter. This very delicate operation was performed under a microscope. A video of the test demonstration was recorded using a CCD video camera. All stages of operation using the electrically controlled PLLA fiber catheter proceeded well.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Targeting noise interception, we studied a novel technique for controlling the elastic coefficient of a piezoelectric lead zirconate titanate (PZT) ceramic by connecting a negative-capacitance circuit that behaves as a "negative capacitor." In this system, the attenuation factor in transmission loss was calculated from the ratio between signals obtained using the PZT system with and without the negative-capacitance circuit. The maximum attenuation factor in transmission loss was 57 dB.

DOI： 10.1080/00150190701353036

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Poly-L-lactic acid (PLLA) has recently attracted attention as a polymer which exhibits a high shear piezoelectric constant. In this study, it was possible to control the piezoelectric motion of the PLLA fiber by applying d.c. voltage and a.c. voltage similar to a piezoelectric actuator. Then, on the basis of the experimental results, an electric control catheter and tweezers, using PLLA fibers (PLLA fiber catheter/tweezers) was developed. In the demonstration, it was assumed that thrombosis in blood vessels occurred and it was attempted to remove the thrombosis from the affected area using the PLLA fiber catheter and tweezers. This very delicate operation was attempted under a microscope. Using the PLLA fiber catheter and tweezers, the affected area was excised. A video movie of the test demonstration was recorded using a CCD video camera. All stages proceeded well in this study. Copyright (c) 2006 John Wiley & Sons, Ltd.

DOI： 10.1002/pat.817

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

We report a novel elasticity control technique for piezoelectric lead zirconate titanate (PZT) ceramics using an electric circuit that behaves as a "negative capacitor" (hereafter referred to as a negative-capacitance circuit) for application to sound shielding technology. A feature of this technology using an optimized negative-capacitance circuit is effective sound attenuation regardless of the PZT ceramic type or frequency ranges of the noise. In this experiment, we prepared three types of PZT ceramic with different dielectric and piezoelectric characteristics. We improved the circuit constants of negative-capacitance circuits for the three kinds of PZT ceramic with different physical properties. We measured the transmission loss attenuation factor of the three types of PZT ceramic in the frequency range from I to 100 kHz. We found that the transmission loss attenuation factors of all three types of ceramic were greater than 20 dB in the frequency range from I to 100 kHz.

DOI： 10.1143/JJAP.45.7422

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

In order to study the light modulation properties due to the electrooptical effect, we prepared piezoelectric poly(L-lactic acid) (PLLA) films by drawing and annealing, and ferroelectric polyurea-5 (PU5) by vapor deposition. In all PLLA films fabricated in this study, we found that light amplitude modulation (LM) caused by applying an electric field occurs, using our experimental system based on the heterodyne interferometry principle. However, the LM was very weak. LM in the recrystallized PLLA film is stronger than those in the other PLLA films. The occurrence of LM in PU5 was confirmed using our experimental system. Such results have not been reported until now. Here, we emphasize that the occurrence of LM in PLLA fabricated by the drawing and annealing method and in PU5 film fabricated by the vapor-deposition method is clarified in this study for the first time.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

We produced a new system for measuring the small photoelastic constant of a polymer thin film with a small birefringence. Using our mesurement system, we evaluated the photoelastic constant of a polymer film in real time by quantitative analysis. Photoelastic constants Of 11.30 x 10(-12) Pa-1 for a cellulose triacetate film and 78-38 x 10(-12) Pa-1 for a polycarbonate film were obtained. Furthermore, we obtained a small photoelastic constant Of 0.12 X 10(-12) Pa-1 for a cycloolefin film for liquid crystal displays, using our new measurement system. This value is very small. We emphasize that, if a small change in retardation and stress cannot be detected simultaneously using our system, then we cannot obtain such a small photoelastic constant.

DOI： 10.1002/masy.200651032

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

In this study, we produced a new system for measuring the small photoelastic coefficient of a polymer thin film with a small birefringence. In the measurement system, a frequency-stabilized transverse Zeeman laser (STZL) was used on the basis of optical heterodyne theory. It is possible to measure the birefringence and principal axis direction of a polymer film within 100 μs. Therefore, we were able to evaluate the photoelastic coefficient of a polymer film in real time with quantitative analysis. Furthermore, we obtained a small photoelastic coefficient of 1.2 × 10 -13Pa -1 of a cycloolefin film for LCDs, using our new measurement system. Its value was very small. Then we measured the temperature dependence of the optical film. We emphasize here that it is impossible to measure such a small photoelastic coefficient of polymer films using the conventional measuring system on the basis of Senalmont method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The possibility has been indicated that a piezoelectric polymer with helical chirality (chiral polymer) such as poly-L-lactic acid (PLLA) shows a large linear electrooptical constant (Pockels effect). However, the linear electrooptical constant of a PLLA film may be very small because such a film fabricated by the conventional method has a complex high-order structure with intermingled crystalline and amorphous regions. In order to measure the small linear electrooptical constant of a PLLA film, we developed a new measurement system, which is based on the heterodyne interferometry principle. In this system, the accuracy of retardation is 0.08 nm and the measurement time is 0.1 s. In our attempt to realize a PLLA film with a large linear electrooptical constant, we fabricated a PLLA film, which was heated to 120 degrees C under 320MPa. Finally, using our new measurement system, we obtained a linear electrooptical constant of 0.070pm/V in the PLLA film, which is very small compared with those of other famous Pockels materials. However, the linear electrooptical constant of the PLLA film is clarified in this study for the first time.

DOI： 10.1143/JJAP.44.7115

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

A piezoelectric material was inserted in an elastic wave vibration transmission system to improve sound insulation. The apparent elasticity of the inserted piezoelectric material was controlled using an electric circuit called a negative-capacitance circuit. We prepared two identical brass bars with a length of 1.5 in and a diameter of 10 mm. The two brass bars were joined with a lead zirconate titanate (PZT) material, and two additional PZT materials were attached to the end of the brass bars. An elastic wave in the ultrasonic frequency range was applied to one end of the bar system and propagated through the bar, the PZT material and the other brass bar. A negative-capacitance circuit was attached to the PZT material. The increase in transmission loss excluding the normally existing loss in the PZT material was measured before and after connecting the negative-capacitance circuit that softens the PZT material. A maximum increase in transmission loss of more than 60% was obtained.

DOI： 10.1143/JJAP.44.7019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

It is difficult to obtain a drawn chiral polymer/inorganic material composite membrane with shear piezoelectricity by the conventional method because the chiral polymer/inorganic material composite membrane breaks during the drawing process by which shear piezoelectricity is realized. Using a strong magnetic field, we propose to manufacture a drawn composite membrane of poly-l-lactic acid (PLLA), a chiral polymer, and hydroxyapatite (Hap), an inoroganic material (PLLA/Hap composite membrane). The manufacturing method used here is effective for obtaining a drawn PLLA/Hap composite membrane with a large uniform area. Also, the shear piezoelectric constant of the drawn PLLA/Hap composite membrane is about 20 pC/N. This value is large for piezoelectric polymers.

DOI： 10.1143/JJAP.44.7119

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We developed an interesting instrument for manufacturing a biodegradable-polymer-insulated cable, with a variety of new functions. Using this instrument, we manufactured a poly-l-lactic acid (PLLA)-insulated cable. We measured the basic electrical insulation characteristic of the PLLA-insulated cable, and the following results were obtained. The mean breakdown strength of PLLA-insulated electric wire was approximately 3.5 times that of a polyvinyl chloride-insulated electric wire (VVF cable). Also, a bending test of the PLLA-insulated electric cable was performed. We obtained good results.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We fabricated poly-L-lactic acid (PLLA) fiber samples using high-speed spinning it? order to improve their piezoelectricity. If an electric field is applied to the PLLA fiber in the direction perpendicular to its fiber axis, the PLLA fiber must be driven by the piezoelectric effect. We developed an effective method of applying an electric field to the PLLA fiber. As a result, we could drive the PLLA fiber by the shear piezoelectric effect under the application of ac voltage, and observed the bending motion of the entire PLLA fiber. Next, we have designed tweezers using a pair of PLLA fibers controlled by applied ac voltage, and have pursued the realization of PLLA fiber tweezers; finally, this was achived. On the basis of our experimental results, we believe that there is a high possibility of realizing the PLLA fiber tweezers for the manipulation of soft and minute samples such as biological cells.

DOI： 10.1080/00150190590966982

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

We produced a new system for measuring the small photoelastic coefficient of polymer thin film with a small birefringence. In the measurement system, a frequency stabilized transverse Zeeman laser (STZL) was used on the basis of Optical heterodyne theory. It is possible to measure the birefringence and principal axis direction of a polymer film with a high retardation accuracy of more than 0.04nm in the temperature range from 20°C to 250°C.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A polymer that consists of the ethylene oxide unit and another characteristic group, such as mesogenic 4-cyano-4'hydroxydiphenyl, as two end groups was synthesized. New polymer complex films (PCFs) were obtained using the synthesized polymer and a salt. The temperature dependence of the frequency spectra of the linear to third-order nonlinear complex conductivities of the PCFs was measured. The PCFs show unique third-order nonlinear conductivity phenomena. The frequency spectra of linear and nonlinear conductivities of PCFs are reproduced by linear and nonlinear conductivity relaxation functions. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elstat.2004.04.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

The possibility has been indicated that polymers with helical chirality, such as poly-gamma-benzyl-L-glutamate (PBLG) and polyL-lactic acid (PLLA), exhibit a large shear piezoelectric constant. To attempt the realization of a PBLG membrane with a large piezoelectric constant, we fabricated the PBLG membrane oriented by magnetic field force. Concretely, the PBLG membranes were casted from 1,2-dichloroethane solution with various PBLG concentrations under the magnetic field generation equipment incorporating a superconducting magnet. First, the orientation of the chain molecules of the PBLG membranes obtained was observed macroscopically by means of a polarizing microscope (POM). The orientation of the chain molecules of the PBLG membranes was recognized for the case of casting from the PBLG 1,2-dichloroethane solution in the liquid crystal state. Also, from X-ray photograph measurements, it was found that the orientation direction of the chain molecules of PBLG was perpendicular to the magnetic field direction. We then measured the shear piezoelectric constant d(14) of the oriented PBLG membranes. With increasing the strength of the applied magnetic field in the casting process for the film preparation, d(14)* of the PBLG membranes obtained increases. Finally, a large piezoelectric constant of 26 pC/N was found in the PBLG membrane. It is assumed that d(14)* is not saturated even at the magnetic field of 10 T.

DOI： 10.1143/JJAP.43.6769

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We measured the basic electrical insulation characteristic of biodegradable polylactic acid (PLA), and the following results were obtained. The volume resistivity, dielectric constant, and dielectric loss tangent measured at room temperature were almost the same as those of crosslinked,polyethylene (XLPE) currently used as insulating material for cables and electric wires. The mean impulse breakdown strength of PLA was about 1.3 times that of XLPE. Also, space charge accumulation in PLA and XLPE was measured. The amount of space charge accumulation in PLA was one-half that in XLPE when dc voltage was applied for a short time.

DOI： 10.1109/TIA.2004.830751

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Polylactic acid (PLA) is a polymer material on which biodegradability research has been the most advanced. PLA is a chiral polymer in which molecules containing asymmetric carbon atoms have a helical structure. Two optical isomers of PLA exist, PLLA (poly(L-lactic acid)) and PDLA (poly(D-lactic acid)). In this study, using various physical processes, we fabricated various samples such as oriented PLLA film, PLLA fiber, rolled PLLA film and forged PLLA plate. We observed a large optical rotatory power rho in the cylindrical plate fabricated using a forging process. rho of forged PLLA plates is 7200degrees/mm which is approximately 300 times larger than that of alpha-quartz.

DOI： 10.1002/masy.200450819

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The poly-L-lactic acid (PLLA) shows a high shear piezoelectric constant. We fabricated PLLA fiber samples with large degree of crystallinity and high orientation of crystallites using high-speed spinning. If the electric field is applied to the PLLA fiber in the direction perpendicular to the PLLA fiber axis, the PLLA fiber must be driven by the piezoelectric effect. Therefore, we devised an effective method of applying the electric field to the PLLA fiber. We also developed equipment for measuring the piezoelectric motion of the PLLA fiber, which uses a CCD camera and divided photodiodes. As a result, we could drive the PLLA fiber by the shear piezoelectric effect under the application of ac voltage, and observed the bending motion of the entire PLLA fiber. Finally, we attempted to release and grasp the bead sample using a pair of PLLA fibers like tweezers, and succeeded.

DOI： 10.1080/00150190490460885

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

The possibility has been indicated that polymers with helical chirality, such as poly-L-lactic acid (PLLA), show a large optical rotatory power rho (about 9600 deg/mm: J. Kobayashi et al., J. Appl. Phys. 77 (1995) 2957) or piezoelectric constant in their fiber axial direction (helical chain direction). To attempt the realization of a new optical or piezoelectric active polymer device, we fabricated the PLLA on a basal plate using end-grafted polymer technology. The structure of PLLA on a basal plate was observed by atomic force microscopy. As a result, we found that the PLLA on a basal plate with annealing grows into have a needle-like structure. The roughness of the aggregate PLLA on a basal plate is 12.5 nm. rho of the PLLA on a basal plate is about 80 deg/mm. This rho value is larger than that of the quartz crystal which is a very well-known crystal with high optical activity. We speculated, on the basis of Kobayashi et al.'s report, that the helical chain direction of the PLLA on a basal plate obtained in this study is not perpendicular to but has a fixed angle to the surface of the basal plate.

DOI： 10.1143/JJAP.42.6172

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Recently, much importance has been attached to the problem of environmental pollution by industrial waste products. Recently, biodegradable polymers have attracted interest in that they open the way to an unexplored processing method for the disposal of industrial wastes Polylactic acid (PLA) is the polymer material on which biodegradability research has been the most advanced. Making the most of this advantage, in the future, we plan to apply PLA as an insulating material, for example, in electric wires and cables. For this reason, we measured the basic electrical insulation characteristic of PLA, and the following results were obtained. The measurement results of volume resistivity, dielectric constant and dielectric loss tangent, at room temperature, were almost the same as those of crosslinked polyethylene (XLPE) currently used as the insulating material for cables and electric wire, respectively. The mean value of the impulse breakdown strength of PLA was about 1.3 times that of XLPE. Thus, the possibility of the insulation thickness reduction of electric wire and cable is demonstrated. Also, the space charge accumulation of the PLA and XLPE was measured. The value of the space charge accumulation of the PLLA is half of that of XLPE, when the DC voltage was applied for a short time.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured the frequency dependence of linear to third-order nonlinear complex conductivities and permittivities of a new antistatic polymer film (NASPF), that is, a composite film which consists of highly conductive butadiene rubber (BUT) particles containing Li+ and poly(methyl methacrylate), at room temperature. The nonlinear conductivities obtained allowed an estimate of the important parameters which characterize ionic transport in the composite film, such as the hopping distance of ions or the size of a cluster connected to the site capable of ion hopping, without any additional assumptions. We obtained two hopping distances, 68 and 380 nm. The former may correspond to the distance between adjacent hopping sites in one BUT particle. The latter corresponds to the average size of the clusters formed by some BUT particles, in which ions can move freely. The results are consistent with transmission electron microscopic image data concerning BUT particle dispersion in the NASPF. (C) 2002 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Using new techniques, we fabricated two kinds of piezoelectric films, polyurea-5 and poly-L-lactic acid (PLLA) films, in order to investigate their optical properties, of which the higher order structures are simple. Our main findings are as follows. In the case of the PLLA film fabricated by the new technique, giarit optical rotatory power and high-speed light modulation exists. On the other hand, in the case of the polyurea-5 film prepared by vapor deposition polymerization, the Pockels coefficient of 0.09 pm/V is obtained This value is fairly large for polymers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

In order to investigate the intermolecular interaction between the individual chain molecules which causes the ferroelectric to paraelectric phase transition of ferrolectric polymers, we devised a new experimental system for measuring the transverse sound velocity for polymer films. Using the new system, we measured the transverse sound velocity nu (55) which corresponds to the elastic stiffness tensor component C-55 which reflects the intermolecular interaction between the individual chain molecules (sliding motion between adjacent chain molecules) of the copolymer film of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)). The value of nu (55) obtained here decreases significantly and then reaches a small constant nonzero value, in the temperature range from below the Curie point to the melting point. The results suggest that intermolecular interaction is strong in the ferroelectric phase and becomes very weak in the paraelectric phase, however, the intermolecular interaction between them does not disappear in the paraelectric phase.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

Tn order to investigate the piezoelectric properties of composite films of 0.91Pb(Zn1/3Nb2/3)O-3-0.09PbTiO(3) (PZNT) and polyvinylidene fluoride (PVDF) prepared by the sol-gel method in comparison with those of PVDF, copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)), and polyurea-5, the residual polarization P-r and the electromechanical coupling factor k(33) were measured. The results verified that PZNT- and PVDFcomposite-firm (PZNT/PVDF film) manufacturing method can effectively realize a uniformly large area composite membrane. We obtained the apparent P-r of PZNT/PVDF film in D-E hysteresis measurements. The k33 value of the PZNT/PVDF film is about 0.08. The k(33) value is approximately 1/4 that of the beta -PVDF or P(VDF/TrFE) film.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

In order to investigate the ferroelectric properties of polyurea-5 prepared by vapor-deposition polymerization in comparison with those of polyvinylidene fluoride (PVDF) and copolymers of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)), the residual polarization P-r, the piezoelectric constant e(31) and the Pockels effects were measured. As a result, the P-r values of polyurea-5. PVDF, and P(VDF/TrFE) were obtained as 20 mC/m(2), 60 mC/m(2) and 100 mC/m(2), respectively. On the other hand, polyurea-5, PVDF acid P(VDF/TrFE) showed e(31) of 5 mC/m(2); 60 mC/m(2) and 100 mC/m(2), respectively. We obtained P-r similar to e(31) in the case of P(VDF/TrFE) and PVDF. In the case of P(VDF/TrFE) and PVDF, P-r similar to e(31) has been reported by many researchers. However, in the case of polyurea-5, P-r > e(31) was obtained. The e(31) of polyurea-5 is about 1/20 that of P(VDF/TrFE). Also, to measure the Pockels effects of polyurea-5 films, a laser beam was introduced parallel and perpendicular to the thickness of the polyurea-5 him which was poled at room temperature. As a result, the Pockels coefficient of the polyurea-5 film was obtained to be 0.09 pm/V, which was approximately 1/4 that of PVDF or P(VDF/TrFE) films. however, this value is fairly large for polymers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

In order to investigate the ferroelectric properties of polyurea-5 prepared by vapor-deposition polymerization, we used switching measurements and found that polyurea thin films showed ferroelectric polarization reversal behavior. Ferroelectric switching transients with the amount of reversed polarization P-r of 20mC/m(2) were observed for the polymer thin film at room temperature. This P-r is consistent with a polyurea-5 film crystallinity of 30%. We then found a two-step increase in the switching transients above 50 degrees C. The first increase fives P-r of 20 mC/m(2) and the second increase gives a large P-r increment of 200 mC/m(2) which is much larger than the calculated value of the spontaneous polarization in the single crystal of polyurea-5. However the second increase with P-r of 200 mC/m(2) is almost independent of applied field E and shifts to short time regions with increasing E. These results imply that the second increase with P-r of 200 mC/m(2) is caused by ferroelectric switching.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The temperature dependence of the frequency spectra of linear to third-order nonlinear complex conductivities in tetraethylene oxide-organosiloxane copolymer/LiClO4 complexes was measured. At each temperature, a characteristic conduction relaxation phenomenon was observed in the spectra, which suggested the existence of different ion conduction mechanisms between the low-and high-frequency regions. We found that the ratio of linear to nonlinear conductivities was closely related to the elementary process of ionic transport in the samples. Without the need for any additional assumptions, we also found that the ratio obtained from nonlinear measurements allowed an estimate of the important parameters which characterize ionic transport in the samples, such as the size of a connected cluster of the site capable of ion hopping or the hopping distance of ion. (C) 1998 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

Vinylidene fluoride and trifluoroethylene copolymers (P(VDF/TrFE)) are ferroelectric polymers. P(VDF/TrFE) are crystallized in a paraelectric phase under special conditions, P(VDF/TrFE) formed a highly double-oriented crystalline film with no noncrystalline areas or lamella crystals. This film does not have a single-crystal structure, but has far more single-crystal-like features than any other solid polymeric material. Accordingly, it has been reported as a "single-crystalline" film (SCF) by Ohigashi et al. [Appl. Phys. Lett., 66, 3281 (1996)]. We investigated the formation process of a SCF by measuring its double refractive index. Furthermore, we evaluated the relationship between the degree of polarization and the degree of Pockels effect of the SCFs, by measuring the Pockels effects and the D-E hysteresis simultaneously The Pockels coefficients of the SCFs were in proportion to the degree of polarization. The maximum Pockels coefficient of the SCFs obtained was 2.82 pm/V, which is 7 times higher than that of conventional lamella films of ferroelectric polymers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured the frequency dependence of linear to third-order nonlinear complex conductivities in tetraethy lene oxide-organosiloxane copolymers. A characteristic conduction relaxation phenomenon was observed in the spectra, which suggested the existence of different ion conduction mechanisms between the high-and low-frequency regions. We also found that the ratio of linear to nonlinear conductivities was closely related to the elementary process of ionic transport. Furthermore, the ratio obtained from nonlinear measurements allowed the estimation of the important parameters which characterize ionic transport in polymers, such as the hopping distance of ions or the size of a connected cluster in the site capable of ion hopping, without the need for any additional assumptions.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

Ferroelectricity in vinylidene fluoride (VDF), trifluoroethylene (TrFE) and hexafluoropropylene (HFP) copolymers (P(VDF/TrFE/HFP)) with a low HFP content (lower than 11mol%) has been investigated primarily through switching measurements using P(VDF/TrFE) as a comparison. Switching phenomena as a result of ultimately 180 degrees rotations of individual molecular chains around their axes in crystalline regions were observed in P(VDF/TrFE/HFP) with an HFP content lower than 2.5 mol%. With increasing HFP content in P(VDF/TrFE/HFP), the amount of reversed polarization decreases, and the dielectric permittivity at the Curie point becomes smaller. However, the switching times have very low dependence on the HFP content of P(VDF/TrFE/HFP). These results suggest that noncrystalline regions in P(VDF/TrFE/HFP) are similar to those in P(VDF/TrFE), and the disorder in crystalline regions of P(VDF/TrFE/HFP) increases compared to that in crystalline regions of P(VDF/TrFE).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

''Single crystalline'' (SC) films of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymers (P(VDF/TrFE)) which are highly double-oriented films, do not form an intricate highly ordered structure, for example, a lamellar structure, but a simple one. After a SC film is poled under a de electric field, one-to-one correspondence can be observed between the macro-(drawn and poling axes) and optical axes in a SC film of P(VDF/TrFE). Therefore; linear electrooptical effects of SC films of P(VDF/TrFE) can be measured at room temperature and constant stress. We then found a large electrooptical coefficient in SC films of P(VDF/TrFE).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

Thin polyurea-5 films were prepared by vapor-deposition polymerization of 1,5-diaminopentane and 1,5-diisocyanatepentane. In order to investigate the ferroelectric properties of polyurea-5, we measured switching behavior. Switching phenomena were observed for the polymer thin films at room temperature. It was found that the switching time depends on the applied electric field E, and that the amount of reversed polarization is nearly independent of E. The results clearly revealed characteristics of ferroelectric switching phenomena. As a result; we obtained a residual polarization of about 20 mC/m(2) at room temperature. We found also that the switching time is long, and that the shape of switching curves is broad, compared to those of typical ferroelectric polymers, vinylidene fluoride and trifluoroethylene copolymers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

Thin polyurea-5 films were prepared by vapor-deposition polymerization of 1,5-diaminopentane and 1,5-diisocyanatepentane. In order to investigate the ferroelectric properties of polyurea-5, we used dielectric hysteresis measurements. Ferroelectric hysteresis loops were observed for the polymer thin him at room temperature. The dielectric hysteresis curve shows large polarization values above 70 degrees C, which are much larger than the calculated value of the spontaneous polarization in the single crystal of polyurea-5. To evaluate the residual polarization, sinusoidal electric fields with varying frequency were applied at various temperatures and the time variation of the electric displacement was detected by a charge amplifier. As a result, we obtained a residual polarization of about 25 mC/m(2) at temperatures in the range of 20-70 degrees C. This value is consistent with a polyurea-5 film crystallinity of 50%.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

A new experimental system has been developed, which enables measurements of linear as well as non-linear complex conductivities to be made. The frequency dependence of linear to fifth-order non-linear complex conductivities at different temperatures in a polyethylene oxide/salt complex can then be measured. A characteristic conduction relaxation phenomenon was observed in the spectra, which suggested the existence of different ion-conduction mechanisms between the high- and low-frequency regions. It was also found that the ratio of linear to non-linear conductivities was closely related to the elementary process of ionic transport. Furthermore, this ratio obtained from non-linear measurements allowed an estimate of the important parameters which characterized ionic transport in ion-conducting polymers, such as the hopping distance of an ion or the size of a connected cluster of the site capable of ion hopping, without the need for any additional assumptions. Thus, it was found that in a polyethylene oxide/salt complex, the typical size of a connected cluster of the effective sites capable of ion hopping was approximately 4 nm.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

The effects of thickness on ferroelectricity in vinylidene fluoride and trifluoroethylene copolymers have been investigated mainly through switching measurements. Switching phenomena as a result of ultimately 180 degrees rotations of individual chain molecules around their axes were observed in the copolymer films with thicknesses in the range of 0.03-1 mu m. With decreasing film thickness, the switching times increase, the switching curve becomes,road and the permittivity at the Curie point decreases. However, the amount of reversed polarization is nearly independent of film thickness. These results are generally reproducible if we assume a surface layer with thickness less than 0.01 mu m low permittivity, and absence of ferroelectric switching even in the presence of an applied electric field.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publisher：ELSEVIER SCI LTD  

Tetraethylene oxide-organosiloxane hybrid (TEOS), a flat membrane, was obtained by mixing solutions of tetraethylene oxide and methyltrichlorosilane in a Teflon vessel. In the frequency spectra of the linear conductivity of the ionically conductive membrane using TEOS as a matrix (TEOS/LiClO4), relaxations associated with the electrode and interfacial polarizations were observed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

Ferroelectric copolymers of vinylidene fluoride with trifluoroethylene and tetrafluoroethylene have been investigated by means of broad band dielectric spectroscopy (10 mHz-1 GHz) at temperatures covering the ferroelectric, paraelectric and molten phases as well as the glassy and rubbery states. The low-temperature relaxation spectra near T(g) (approximately -40-degrees-C) consist of two processes; a WLF-type segmental mode and an Arrhenius type local mode. these processes are unified near room temperature to be transferred continuously to the high-temperature process. After showing a peak at the Curie point T(c) (70-140-degrees-C), the relaxation strength decreases gradually in the paraelectric phase until the melting point T(m) (approximately 150-degrees-C) is reached, where it decreases rapidly. It is found that the relaxation time in the molten phase lies on the Arrhenius line extended from the low-temperature local mode process. Tbis implies that related molecular motions arise from a common elementary process. Departure from this Arrhenius line in the paraelectric phase is discussed by the use of a cooperative multi-site model.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

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Language：English   Publishing type：Research paper (scientific journal)  

Ferroelectric switching characteristics of vinylidene fluoride/trifluoroethylene copolymers have been investigated in relation to their higher order structures and compositions. The amount of reversed polarization increases with increasing crystallinity and drawing. This is consistent with the assumption that the switching occurs as a result of rotations of molecules around their chain axes in the crystalline regions. The switching time follows an exponential law at fields from 50 to 500 MV/m. Extrapolation to the infinite field predicts the switching time of 1-10 nsec. © 1985 The Japan Society of Applied Physics.

DOI： 10.7567/JJAPS.24S2.859

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARCEL DEKKER INC  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

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Language：English   Publisher：JAPAN J APPLIED PHYSICS  

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Catheters for thrombosis sample in blood vessels using piezoeletric polymer fibres

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