高深寬比微型多探針電極陣列系統

High Aspect Ratio Micro Multi-Probe Electrode Array System

陳昶孝(Chang-Hsiao Chen)

指導教授 ： 饒達仁

國立清華大學/工學院/微機電工程研究所/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00381

摘要

本研究主題為開發一〝微型多探針電極陣列之神經訊號量測系統〞，研究最終目標將朝向腦科學生物醫學檢測運用。為了要完成此量測系統，本論文將會以微型多探針電極陣列的設計和製作為主，並進行探針電極之強度與效能測試，以利將來完整系統的研發。
人腦由超過一千億個可傳遞電信號的神經元聚集而成的複雜系統，其信號傳遞過程中屬網路型觸發。由於考慮將應用於大腦皮層神經信號量測，微探針將被刺入，故探針強度將備受考驗。在設計完整的微探針製程之前，先行以ANSYS模擬各式幾何形狀，進而得到最佳化的微探針尺寸。從模擬結果可得之，以1/4圓切加支柱的根部設計，能承受最大的穿刺力量(18.5mN)。
接下來，微機電製程技術將被運用在微探針陣列的製作上。主要架構在矽底材微機械加工基礎上，並以SOI wafer為製程基材。製程主要含括：黃光微影、高溫成長、乾式蝕刻、CVD、PVD…等基本技術、在雙層矽晶片上開發出微電極陣列之結構，其優勢為將使得製程簡易，並提高製程的良率及均勻性，其良率可達98%。製程特色上，微探針厚度將取決於Device Si Layer厚度，可達精確厚度控制。
另以電化學交流阻抗分析法為基礎，架構一系統用於量測微電極與電解液之間的阻抗與相位，進而求得電雙層電容值。此資訊有利於未來電極量測神經信號前置處理的電路架設，避免負載效應，幫助調配匹配電阻，亦使OPA自身雜訊下降和避開高通濾波器之截止頻率，進而達到原始神經信號重現。微電極在AMES溶液中，平均阻抗為2.46MΩ/ 1KHz。
未來目標，初期先行整合元件與前級電路，此重點於降低雜訊對神經信號的影響。二期目標進行生物大腦皮層實體量測實驗，量測系統架設是其關鍵。最後目標將是置入藥物傳輸的微流道，以達主動型
醫療機制。

關鍵字

微探針 ； 電極陣列

並列摘要

This research is to design a “Micro Multi-Probe Electrode Arrays for Neural Signal Recording System”. The final goal is to apply the measurement system on bio-medical applications. Based on the optimal design of micro multi-probe electrodes by Ansys, the fabrication of electrodes can be accomplished by using MEMS technology. At the end, the performance of electrodes would be measured, which will be very useful for further development of measurement system.
Brain is a complicated system that sends electrical signal by thousand hundred million neurons. The process of signal is a very complicated network. As a result of the micro probe electrode would be used to measure neural signal of brain cortex, the intensity of electrode is very critical. Several kinds of geometry were applied to simulate by ANSYS before designing fabrication process. The shank geometry 1/4 Cycle (Pillar) is the proper one that can bear 18.5mN force.
MEMS technology was used to develop the fabrication of micro multi-probe electrodes, which started by using SOI wafer. Lithography, LPCVD, dry etching, PVD, etc were used to develop the micro electrodes on the SOI wafer. The yield of designed fabrication can reach 98%. The feature of process inherently can control the final probe thickness based on the thickness of device layer of the SOI wafer.
Then we used the electrochemical alternative current impedance analysis to measure the impedance and phase between electrode and electrolyte, and then to obtain the capacitance of electrode double layer. It is beneficial for us to set up the circuit of the further jobs in the future. To avoid the loading effect, it is useful to allocate the suitable matching resistance, which could be used to decrease the noise of OPamp and decide the proper cut frequency of high pass filter in order to to obtain the original neural signals.
Future work is to use current accomplished results to for developing a completed measurement circuitry. To reduce noise of the neural signal is very important. The final goal is to implant multi-channels by using developed electrode array and to inject medicine for some medical treatments.

參考文獻

[5] T. U. T. Kikuchi, T. Ichiki, and Y. Horiike, "Fabrication of quartz micro-capillary electrophoresis chips for health care devices," presented at Conferences of Microprocesses and Nanotechnology, Yokohama, Yokohama, Japan, July, 2001.

[6] K. D. Jandt, "Atomic force microscopy of biomaterials surfaces and interface," Surface Science, vol. 491, pp. 303-332, 2000.

[8] L. L. M. Meister, and D. A. Baylor, "Concerted signaling by retinal ganglion cells," Science, vol. 270, pp. 1207-1210, 1995.

[9] D. K. W. I. H. Brivanlou, and M. Meister, "Mechanisms of concerted firing among retinal ganglion cells," Neuron, vol. 20, pp. 527-539, 1998.

[10] S. H. DeVries, "Correlated firing in rabbit retinal ganglion cells," Journal of Neurophysiol, vol. 81, pp. 908-920, 1999.