Study on Liquid-Crystal Based Micromachined Tunable Capacitors
Date Issued
2007
Date
2007
Author(s)
Chung, Sheng-Yuan
DOI
en-US
Abstract
This thesis presents a tunable power harvesting device and explains how a tunable capacitor based on polymer-dispersed liquid crystal (PDLC) can be used to optimize the power harvesting efficiency. The power harvesting device utilizes piezoelectric micro-cantilever excited by environmental random vibration to transfer mechanical energy to electric power. For improving the power harvesting efficiency, we have developed a PDLC tunable capacitor to adjust the resonance frequency of the piezoelectric micro-cantilever beam to match the frequency of environmental random vibration in real time. Fabrication process and measurement results of the PDLC tunable capacitor are detailed. Large tuning ratio up to 117.5% of the PDLC tunable capacitor is measured at 75kHz signal frequency. At 12V driving voltage, tuning ratio as 55% can be achieved. The dielectric and optical properties of the fabricated tunable PDLC capacitor have been examined thoroughly. Based on the experimental results, we have also developed an equivalent lumped-element model of the PDLC tunable capacitor. The simulation results show that the impedance of the developed model agrees well with that of the fabricated tunable capacitor. This model can be incorporated into the equivalent circuit of the integrated power harvesting system for efficiency optimization in the future.
Subjects
可變電容
能量擷取
tunable capacitor
power harvesting
polymer-dispersed liquid crystal
Type
thesis
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