Dynamic Behavior Investigation of the Piezoelectric PVDF for Flexible Fingerprint
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0949-C06-06
Dynamic Behavior Investigation of the Piezoelectric PVDF for Flexible Fingerprint Wen-Yang Chang1,2, Ying-Hui Cheng2, Shu-Yuan Liu2, Ying-Chiang Hu2, and Yu-Cheng Lin1 1
Department of Engineering Science, National Cheng Kung University, 1 University Road, Tainan, 701, Taiwan 2
Microsystems Technology Center, Industrial Technology Research Institute, No.31, Gongye 2nd Rd., Annan District, Tainan, 709, Taiwan ABSTRACT This study reports a flexible technology for identifying the fingerprints using the piezoelectric polyvinylidene fluoride (PVDF) materials. The flexible PVDF has successfully developed to identify the fingerprints by an electric charge of the piezoelectric character. The fingerprint sensors were fabricated using the polymer MEMS (micro electromechanical systems) technologies and integrated into the flexible polyimide substrate. The study focuses on the 3D array fabrication for reducing surface tension of each PVDF pixel and the dynamic control circuit for acquiring the piezoelectric signals. Experimental results show the 3D array patterns by pressing on PVDF film have a good structure, and each pixel is more freedom that means the pixel is unrestricted on top surface and can reduce the couple effect of each pixel. The depth of micro array is about 15 m and the response speed of the flexible fingerprint sensors are as fast
μ
as 5 ms. Therefore, the aim of this study is to speed up the technology for promoting the flexible fingerprint. The feasibility studies also show the molding transfer is an appropriate low-cost technology for fabricating of the flexible piezoelectric fingerprint sensor. Furthermore, the PVDF has a good mechanical strength and electrochemical stabilities for fingerprint sensor applications. INTRODUCTION The flexible electronic display and paper have been developed rapidly in recent years [1-3] for new product applications. In general, the current studying used a soft power switch to control ON or OFF of the flexible products. Therefore, in our study, we try to use the flexible fingerprint identification (FI) of the piezoelectric PVDF as secret controlling switch for protecting private secrecy. However, the traditional FI sensors that based on the hard substrate are difficult to become softer and integrate to flexible products. There are mainly two types of the FI sensors: optical sensors [4] and solid state [5-8]. The optical FI sensors need an illuminative component and to make level for recognizing sensing. Observably, it is not convenient for the portable usage and flexible bending repeatedly. The solid state sensors were usually designed as a capacitance
[5], a pressure [6], or a thermal foil type [7] structure. These fabricated technologies include the complementary metal oxide semiconductor (CMOS) [8] and micro electromechanical system (MEMS) [2]. It also knew that most of the solid state sensors are not suitable for bending usage and cannot be fabricated easily. Thus, the few researchers have been recently studied the flexible FI, as the Hiroki [9] proposed a
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