植入式生醫微型系統之無線電源傳輸 製作與其電源傳輸於生物組織之探討

Development of Wireless Power Transmission for Implantable Biomedical Microsystems and Study of Power Transmission in Bio Tissues

陳宏榮(Hon-Zon Chen)

指導教授 ： 婁世亮

中原大學/工學院/醫學工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400666

摘要

中文摘要

生醫植入式微小化系統的能量來源可分為：(1)於植入式系統內置電池作為能量來源，(2)外部電源傳輸能量．以外部電源傳輸能量的好處是植入式生醫元件的壽命不會因為電源耗盡而必須更換，但是缺點是外部電源若為有線傳輸，則可能有傷口感染的可能，若為無線傳輸，則無線電源會受到生物組織的阻礙而影響植入式元件的正常功能，本篇論文中主要是探討以RF無線功率傳輸技術作為植入式電子生醫元件及系統所需的電源供應及資料傳輸的方式，首先介紹生醫植入式微型系統及以E級功率放大器作為其能量傳輸，我們將解釋class E功率放大器的基本線路及生醫植入式電刺激器的線路基本架構並製作可調整四種不同振盪頻率之class E振盪線路．在理論中闡述RF電源線圈耦合原理及影響電源耦合的基本因素，介紹發射線圈幾個種類與我們所採用的線圈的磁場分布，並介紹在組織細胞中，影響組織對於RF能量吸收的因素．我們探討植入式能量接收元件在四種振盪頻率下，於生物體中與在空氣中時所能接收到的能量之差異，本實驗採用豬肉脂肪與豬里肌肉作為生物材料，探討在發射線圈與接收線圈之間的材料之介電係數，高度，截面積與在接收線圈下方的包覆材料與接收線圈所接收到的能量的關係．本研究發現，低頻的傳輸效率低於高頻的傳輸效率，然而，在低頻中，接收功率的衰減比高頻較為緩慢，換句話說，低頻具有較高之穿透性．除此之外本研究發現，在高介電係數材料中，能量衰減的速度較低介電係數材料緩慢．吾並建立一套評估模式，可用於評估一植入式元件置於一豬肉材質中時，可能所能接收的功率．

關鍵字

生醫植入式微型系統 ； class E功率放大器 ； RF無線功率傳輸技術 ； 電源耦合理論

並列摘要

Abstract

The power energy of bio-implantable microsystems can be provided from (1) conventional wire cord, (2) battery, and (3) an external power transmission system. Unacceptable problems of cosmesis, maintenance, and infection hinder the wire cord development. Life-span issues of battery technologies limit its applications in bio-implantable Microsystems. The advantages of the external power transmission system include continuous availability of power to an implanted unit, and ability to control the implanted unit with the external device using the same radio frequency (RF) link. However, the wireless power transmission systems use RF techniques which the carried power can be attenuated by tissues. Thus, a common question is raised that for a given communication bandwidth how far away the microimplant can be positioned underneath bio tissues so that the microimplant can properly function as it is designed for.
In this research course, we developed a wireless RF power transmission/receiving system to investigate the issue stated above. A major component in the system, a class E power amplifier, is introduced. Four RF resonant frequencies to transmit power in a fashion of electromagnetic wave (EM) were implemented. Protocols of studying power transmission in air and in pork were designed. Instead of human body, this study used pork as bio tissues for the experiments.
Our study results prove that for the coil based power coupling technique transmission efficiency of low frequency EM is less than that of high frequency EM. However, the decreasing speed against distance (or thickness of medium) is slow for low frequency EM comparing with high frequencies. In other words, low frequency EM waves have better penetration capability.
In addition, the study results demonstrate that for all used frequencies high dielectric constant (ε) media such as pork lion attenuate power most. The power attenuation rate of high ε, on the other hand, is slower when the thickness increases comparing with low ε.
Most importantly a mathematical model (i.e. assessment model) that can be used to assess power received beneath bio tissues was developed. By using this model, when a microimplant to be placed within bio tissues, its position, in terms of thickness of the bio tissues, and the power received can be easily obtained.

並列關鍵字

coil coupling ； class E power amplifier ； Bio-implantable Microsystems ； RF wireless power transmission

參考文獻

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“Transcutaneous, dual channel phrenic nerve stimulator for diaphragm