Yung Ting

A New Approach of Polyvinylidene Fluoride (PVDF) Poling Method for Higher Electric Response

Good response, in particular high sensitivity, of polyvinylidene fluoride (PVDF) attracts a lot of research works on its manufacturing process and applications. Polarization is an important factor that is influential to the performance of PVDF. In this article, a new polarization method using ITO (Indium Tin Oxide) glass is proposed. Different from the conventional poling method using metal eletrode coated onto PVDF film, ITO glass is used as electrode to transmit the electric field voltage into PVDF film for poling. With the advantage of applying higher electric field in the process of polarization and eliminating the occurrence of flashover and arcing efficiently, this approach can thus make PVDF film gain better electric output response. Also, thinner film is constructed would be another advantage of sensitivity improvement. Comparison with conventional method for regular polarization area is carried out by using both FTIR and DSC equipment. Piezoelectric charge constant d33 and electricity output response as well as sensitivity of PVDF are measured in experiment, which indicate ITO glass poling method is superior to conventional technique.

Investigation of energy harvest and storage by using curve-shape piezoelectric unimorph

A curve-shape piezoelectric unimorph is used for energy harvest. Deformation of the unimorph will gain electricity via piezoelectric direct effect. In this study, a cantilever unimorph encountered with external force at various vibration frequencies to generate electricity and save into a storage circuitry is investigated. Modeling of the unimorph and storage circuitry is derived. The analytical computation and experimental result are in a good agreement. Both outcomes verify that vibration frequency nearer the resonant frequency will gain more energy and the load resistance of a RC storage circuitry matching the equivalent impedance of piezoelectric ceramics will gain maximum storage energy. Efficiency of electromechanical conversion and energy storage is examined. As compared to other previous works using piezoelectric ceramics, the curve shape unimorph performs better. In experiment, for instance, by using a load resistor of 3kΩ ideally equal to the impedance of ceramics and an arbitrarily chosen capacitor of 470µF at vibration frequency of 135.59Hz for 25 seconds, electric power of 48mW is obtained and electromechanical efficiency of about 18.49% is achieved.

In-TFT-array-process micro defect inspection using nonlinear principal component analysis.

Defect inspection plays a critical role in thin film transistor liquid crystal display (TFT-LCD) manufacture, and has received much attention in the field of automatic optical inspection (AOI). Previously, most focus was put on the problems of macro-scale Mura-defect detection in cell process, but it has recently been found that the defects which substantially influence the yield rate of LCD panels are actually those in the TFT array process, which is the first process in TFT-LCD manufacturing. Defect inspection in TFT array process is therefore considered a difficult task. This paper presents a novel inspection scheme based on kernel principal component analysis (KPCA) algorithm, which is a nonlinear version of the well-known PCA algorithm. The inspection scheme can not only detect the defects from the images captured from the surface of LCD panels, but also recognize the types of the detected defects automatically. Results, based on real images provided by a LCD manufacturer in Taiwan, indicate that the KPCA-based defect inspection scheme is able to achieve a defect detection rate of over 99% and a high defect classification rate of over 96% when the imbalanced support vector machine (ISVM) with 2-norm soft margin is employed as the classifier. More importantly, the inspection time is less than 1 s per input image.

A novel approach to generate artificial outliers for support vector data description

In this paper, we propose a novel approach to generate artificial outliers for support vector data description with boundary value method. In SVDD, the width parameter s and the penalty parameter C influence the learning results. The N-fold M times cross-validation is well-known and popular scheme to calculate the best (C , s ) values. To automatically optimize the identification rate, we need more outliers. Due to this reason, we utilize boundary value in any two dimensions randomly to generalize new outliers. At the last, we use three benchmark data sets: Iris, Wine, and Balance-scale data base to validate the approach in this research has better classification result and faster performance.

A novel approach of feature classification using Support Vector Data Description combined with interpolation method

In this paper, we propose a novel approach to feature classification using support vector data description (SVDD) combined with interpolation method. In SVDD, the width parameter s and the penalty parameter C influence the learning results. The N-fold M times cross-validation method is well-known and popular scheme to calculate the best (C, s ) values. To automatically optimize the identification rate, we need more outliers. Due to this reason, we utilize the interpolation method to generalize new outliers. At the last, we use four benchmark data sets: Iris, Wine, Balance-scale, and Ionosphere four data base to validate the method in this research has better classification output and faster performance.

A New Approach for Surface Poling of Polyvinylidene Fluoride (PVDF)

PVDF has been popularly used for miscellaneous sensor and energy harvesting purposes. The advantages of flexible and light characteristics in particular enhance more interest. A new approach of using ITO glass for surface poling is investigated in this study. Instead of using metal electrode onto the PVDF surface, ITO is coated onto glass for conducting electrode. It can provide an easy way of electrode pattern design. Also, higher electric field can be applied in the process of poling so that higher response is achieved. Properties of PVDF films are characterized by using d31 meter to measure the piezoelectric constant and using Fourier Transformed Infrared Spectroscopy (FTIR) and Differential Scanning Calorimeter (DSC) to measure β-crystallization. From the experiment results, it indicates that PVDF film makes use of the ITO glass poling method will gain higher output voltage and current as compared to traditional poling technique. Comb type electrode pattern, for example, is efficient to generate higher output response for planar polarization and is able to control the desired output voltage and current. Using a whole piece of ITO glass for poling with pattern design can avoid from the defect of non-uniform polarization at the corners that usually happens in using metal electrode. Compared to the PVDF embedded in a cantilever and a pressing structure, the latter one will gain more output response.

Evaluation of energy harvesting by using piezoelectric unimorph ceramics

By using the piezoelectric direct effect, piezoelectric energy harvesters hold the promise of providing an alternative power generating device. Also, ambient vibration is the focus to provide the amount of available mechanical energy resource that can be converted into electricity by piezoelectric ceramics. Design and analysis of the piezoelectric unimorph ceramic and electric converter as well as efficiency of electromechanical conversion and energy storage is studied in this article. In experiment, electric power 33.84mW is gained by a capacitor 470µF and a load resistor 10.4M-ohm at low operating frequency of 2.5Hz for 25 seconds, for example. The effectiveness of this electric power to fully charge a NiMH battery only needs 30 minutes.

Experimental investigation of electrode pattern design for PVDF response

Polyvinylidene fluoride (PVDF) films widely used in many applications is due to its flexibility, good response and sensitivity. Electrode pattern is one of the primary factors that are influential to the performance of PVDF films. Different design of electrode pattern influences output response of PVDF. In addition, structure system which demonstrates input energy and output response has correlation with electrode pattern design. In this article, three types of PVDF films including unimorph, stack, and zig - zag, are investigated and compared. Bending moment imposing to a cantilever structure and force directly pressing onto the PVDF films structure are both concerned in experiment. From experimental results, both d33 and d31 piezoelectric charge constants show simultaneous response in consequence of a force applied onto PVDF films. Furthermore, d31 response is larger than d33 for both structures, which indicates d31 constant contributes more response in PVDF films. This phenomenon is useful to define kind of structure system so that optimum response of PVDF films can be achieved.

Circuitry design for direct wind energy harvest system

A wind energy harvest system by using piezoelectric polyvinylidene fluoride (PVDF) is proposed and investigated in this research. Nozzle accelerator is designed to collect wind from environment and increase wind velocity. Using the wind induced drag force to directly blow and vibrate the PVDF employed on the subsequent duct is a simple structure of generating electricity by means of piezoelectric direct effect. Battery-support pull-up circuitry is designed to harvest very small amount of electricity from PVDF.

Using piezoelectric sensor and actuator for ultrasonic assisted system

ABSTRACT An ultrasonic assisted system mainly consists of the transducer and the match-fitting cutter is designed to provide miniature vibration amplitude. In the transducer, a set of piezoelectric ceramics is used as actuator in charge of generating large enough vibration amplitude, which will be immediately measured by the neighboring sensor also made by piezoelectric ceramics. Since the driving frequency is easily affected by the changing working environment, variation of the vibration output is detected in time by the PZT sensor to support the feedback autoresonance control purpose. However, measurement on the transducer is not equivalent to that on the cutter. Further investigation on the measured output of the cutter in comparison with that of the transducer is carried out. It is found that there exists a reasonable and predictable relation between them. ANSYS is used for modal and harmonic analysis. The estimated resonance frequency and vibration amplitude are approximate to the experimental results, which verifies the accuracy of the proposed measurement method.