不鏽鋼基板微型能量擷取器之設計與研製

Design and Fabrication of Piezoelectric MEMS Generator Based on Stainless Steel Substrates

施雅蘐(Ya-Shan Shih)

指導教授 ： 吳文中

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00230

摘要

隨著生醫監控與無線感測技術的蓬勃，植入體內之生醫晶片、動物追蹤裝置與座落於高塔的無線感測節點，其所需之功率消耗便成為聚人關注的焦點，進而帶動能量擷取領域的發展。此外，隨著科技進步，CMOS製程造就電子產品不斷微型化，其耗電量也降至微瓦特(micro-watts)的等級。在體積小、所需能耗低的條件下，具有自供電之優勢的微機電系統(Micro electro-Mechanical Systems, MEMS)能量擷取裝置便從眾多解決方式中脫穎而出。
本論文呈現一系列不鏽鋼基板之微機電壓電式能量擷取結構，其能量擷取裝置能將周遭環境之震動能量，透過壓電式懸臂樑轉換為電能，使用的壓電材料為實驗室自製的氣膠沉積系統沉積的鋯鈦酸鉛(PZT)。論文中將介紹四種不同的壓電結構:d31、d33、雙指叉d33與雙震盪子指叉結構的模擬以及其製程與實驗結果，並於末文針對前三種不同卻相似的結構做實驗結果比較與討論。
實驗結果顯示，以不鏽鋼作為基板的微機電壓電能量擷取裝置相較以往的裝置更加穩定與耐震。不鏽鋼基板的可撓性不但降低其共振頻率，同時，也增加了懸臂樑的形變量，因而增加發電輸出量。結果中，d31裝置的能量輸出為10.533 μW，共振頻213.9 Hz；d33裝置也達到了0.214 μW，共振頻136.2 Hz；新設計的雙指叉d33裝置則將原本d33裝置的輸出提升了四倍，達到0.927 μW，共振頻127.9 Hz；而新結構的雙震盪子裝置則是成功地將30 μm基板之共振頻率壓低至27 Hz，50 μm基板降至66.4 Hz，此結構不僅共振頻率低，並具有倍頻之功能，若操作於共振頻的整除數頻率下，可得到多輸出峰值；並預估在10 Hz以下，由於其峰值頻率靠近，可造成寬頻效果，且其峰值大小更接近共振頻輸出效果。此四種結構輸出之電壓皆足以通過一般的整流電路，以方便後端的儲能應用。

關鍵字

PZT氣膠沉積 ； MEMS能量擷取 ； 懸臂樑 ； 壓電能量擷取 ； 不鏽鋼基板 ； 能量擷取 ； 雙震盪器

並列摘要

Of late years, the growing interest in the field of power harvesting technologies has been brought to researchers’ attentions. With the increasing interests in biomedical monitoring and sensor network applications, supplying power to the implanted biochips and wireless sensor devices have become an important issue[1]. Also, due to the miniaturization of electronics devices, the power consuming scale has been lowered to the micro-watts level. Summing up the above reasons, MEMS power harvesting device seems to be an optimistic solution, avoiding power source replacement, which may be impractical in some cases.
In this thesis, miniaturized power harvesting devices based on stainless steels in the form of cantilever beam is presented. Utilizing the lead zirconate titanate (PZT) as the piezoelectric transforming material, the fabricated devices own the ability to scavenge energy from ambient mechanical vibrations. To increase the voltage output, a home-made PZT deposition chamber which could deposit thin films having the thickness as thick as 10μm was used to deposit the PZT layer of the structures. Different harvesting modes of d31, d33, dual layer d33, and a dual oscillator structure are simulated and afterwards discussed. Subsequently, experimental results of the three similar structures are compared.
Experimental results confirm that the stainless steel substrates have superior robustness, allowing the MEMS device to withstand harsher environments comparing to previous researches. The experimental results show that the d31 device is able to provide the output power of 10.533 μW under the resonance frequency of 213.9 Hz; the d33 device is able to give the output power of 0.214 μW, under 136.2 Hz; the dual d33 device can output four folds the output of single d33, which is 0.927 μW, under 127.9 Hz. The fabricated devices are able to generate power output in scales of micro-watts and the voltage outputs have overcome the threshold voltage of a rectifying bridge, enabling the storage of harvested energy. A newly designed structure of dual oscillator is also presented. With the structure of dual oscillator, the device has lowered the resonance frequency to 27 Hz and 66.4 Hz for different thicknesses of substrate, 30 and 50 μm. This structure also enables the up-conversion of the device. The up-conversion effect not only causes multi-peak frequencies, it also broadens the bandwidth of low vibrating frequencies. It is predicted that the device can be able to operate in circumstances under frequencies lower than 10 Hz.

並列關鍵字

aerosol PZT deposition ； MEMS generator ； cantilever beam ； power harvesting ； piezoelectric generator ； stainless steel substrate

參考文獻

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