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URN etd-0731112-105001 Statistics This thesis had been viewed 1795 times. Download 985 times. Author Li-Chung Huang Author's Email Address No Public. Department Mechanical Engineering Year 2011 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 63 Title Isolation of Acoustic Waves in a Sensor Array Utilizing Phononic Crystals Keyword isolation sensor array phononic crystal finite element method. finite element method. phononic crystal sensor array isolation Abstract In recent years, multiple bulk acoustic wave sensors have been fabricated on a single piezoelectric substrate to develop a sensor array for the detection of multiple analyte parameters. However, such an array may induce acoustic interference between adjacent sensors. Phononic crystals are synthetic structures with periodic variation of elastic property. A phononic crystal with band gaps forbids acoustic waves within the frequency ranges of band gaps to propagate through the structure. This study proposes a sensor array consisting of multiple quartz crystal microbalances (QCMs) which are surrounded by phononic crystals. Phononic crystals are utilized for isolating acoustic energy of individual QCM and suppressing the interference. At first, the resonance response of a QCM and dispersion relations of quartz plates with square-lattice phononic crystals were calculated by finite element analysis. When the thickness of the AT-cut quartz substrate, lattice constant, and filling ratio are chosen as 80 μm, 100 μm, and 0.475, a complete band gap occurs from 19.4 to 23.1 MHz and includes the first resonance frequency of the QCM (20.77 MHz). QCM sensor arrays were also simulated by setting the periodic boundary condition. Results show that mode shape of a sensor unit surrounded by six rows of the phononic crystals with band gap has centralized displacement field distribution and acoustic energy attenuation about 30 dB, indicating that the phononic crystals indeed contribute to a confinement of acoustic energy in the individual QCM. Moreover, the sensor arrays with two QCMs were designed based on the simulation results and fabricated by deep reactive ion etching. Measurement results show that the phononic crystal with band gap forbids acoustic waves and contributes to decrease spurious modes in the frequency response of the QCM sensor array. Accordingly, phononic crystal is verified to be capable of suppressing the crosstalk between adjacent QCMs in a sensor array. Advisor Committee Yung-Yu Chen - advisor
Jia-Hong Sun - co-chair
Wen-Ching, Shih - co-chair
Files Date of Defense 2012-05-17 Date of Submission 2012-07-31