Tunable Capacitor Based on Polymer-Dispersed Liquid Crystal for Power Harvesting Microsystems

A tunable capacitor based on polymer-dispersed liquid-crystal (PDLC) technology is presented in this paper. Its application for robust power harvesting microsystems was investigated. The power harvesting device utilized a piezoelectric microcantilever excited by ambient random vibrations to convert...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2008-10, Vol.55 (10), p.2568-2573
Main Authors: SHIH, Wen-Pin, CHUNG, Sheng-Yuan, CHEN, Yu-Yin, WU, Wen-Jong, CHANG, Pei-Zen
Format: Article
Language:English
Subjects:
Applied sciences
Beams (radiation)
Capacitance
Capacitors
Devices
Dielectric, amorphous and glass solid devices
Electric power generation
Electrical engineering. Electrical power engineering
Electronic equipment and fabrication. Passive components, printed wiring boards, connectics
Electronics
Exact sciences and technology
Excitation
Harvesting
Integrated circuit modeling
Liquid crystal
Liquid crystals
Piezoelectricity
Polymers
Power electronics, power supplies
power harvesting
Resonant frequency
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Studies
tunable capacitor
Tuning
tuning ratio
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Summary:A tunable capacitor based on polymer-dispersed liquid-crystal (PDLC) technology is presented in this paper. Its application for robust power harvesting microsystems was investigated. The power harvesting device utilized a piezoelectric microcantilever excited by ambient random vibrations to convert mechanical energy into electric power. For improving the power harvesting efficiency, the PDLC tunable capacitor was used to adjust the resonance frequency of the piezoelectric microcantilever beam to match the frequency of the ambient vibrations in real time. The fabrication process and measurement results of the PDLC tunable capacitor are detailed. The measured tuning ratio of the PDLC tunable capacitor was 63% at 300-Hz excitation frequency when a 25-V driving voltage was applied. The dielectric and optical properties of the fabricated PDLC tunable capacitor have been examined thoroughly. Based on the results of the experiment, an equivalent lumped-element model of the PDLC tunable capacitor has been developed. The simulation results showed that the impedance of the developed model agreed 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.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2008.2003226