壓電超聲波能源轉換器的電彈性理論

Abstract

由於近年來生醫感測系統與微機電技術的整合，許多生醫晶片或生醫感測器的體積已縮小至可植入人體的尺寸而達到可即時監測病患之生理狀態。然而長時間的監測系統需可長期供應的能源以供運作。根據此需求，本論文提出了使用聲波做為能量傳輸的概念，使用壓電材料做為聲波發射器和接收器，目標為將接收器植入人體內與植入式晶片或感測器結合，並由體外之發射器提供超聲波能量經過人體組織至接受器，再轉換成電能並儲存至電池，以隨時提供晶片或感測器使用。 本論文以Mason model為基礎，成功建立一維之壓電能量傳輸模型用以預測能量傳輸之效率。先以此模型萃取壓電材料之參數做為模型參數之基礎，可藉由輸入各材料參數、波傳距離和衰減係數並加以計算後可預測能量傳輸的效率。再者，設計聲阻抗匹配層希望可增加傳輸效率和頻寬。最後實驗驗證部分使用了鋯鈦酸鉛(PZT)壓電材料做為發射器和接收器，鋁合金(6061T6)和壓克力做為雙層聲阻抗匹配材料。並利用洋菜做為模擬人體組織之替代材料用以傳遞聲波能量。理論模擬顯示加上聲阻抗匹配層後功率增益可由-12.4dB增加至-6.9dB，實驗結果顯示可由-12.4dB增加至-9.3dB，在-20dB頻寬部分理論模擬顯示由14%提昇至89%，實驗結果顯示由9%提昇至78%。未來希望可縮小接收器之尺寸以達到可植入人體之目標，並設計後端儲存電路以有效儲存接收之能量。

According to the integration of biosensing system and micro-electro-mechanical systems (MEMS), the size of bio-chip and bio-sensor has been decreased enough to implant into human body. The implanted real-time medical monitoring can be achieved. However, for long term medical care, the power source of implanted chip has been an important issue. This study fuscous on building a piezoelectric acoustic power transmission model which can increase the power gain power transmission system. In addition, adding acoustic matching layers can improve the performance. Utilizing the piezoelectric effect, the acoustic wave provides a feasible way to wirelessly charge the battery of the implanted biochip. The lead-zirconate-titanate (PZT) is used to be the material of transmitter/receiver. Based on the results of the modified matching model, the double impedance matching layers are constructed by the aluminum alloy (6061T6) and polymethylmethacrylate (PMMA or Acrylic). The maximum power gain has been increased from -12.4dB into -6.9dB in simulation and from -12.4dB into -9.3dB in experiment result.