以微機電製程製作微電極作為評估銀、金、鉑三種材料之生物相容性

Abstract

為了更瞭解大腦的功能，利用清醒動物進行神經活動的記錄不可或缺。微機電製程製作的多通道微電極陣列可用來進行長期植入的實驗，但為避免微電極在長期植入後對於生物體可能造成的傷害，因此須先進行各種材料的微電極其生物相容性評估。 本文利用微機電製程以矽為基材製作神經探針，探針的前端有三種不同金屬材質之微電極：銀、金、鉑，以提供植入大鼠腦部皮質區進行生物相容性的評估。為了提高神經探針的生物相容性，使用一個具有良好生物相容性的高分子材料：聚-對二甲苯將神經探針完全包覆。微電極的電氣規格會依製程不同而異，因此微電極製作完成後進行其電氣特性之量測。 本文研發新的製程將聚-對二甲苯包覆在探針之外，以提高神經探針之生物相容性，並測試三種不同金屬材質微電極阻抗之頻率響應。此外本文亦製作前端濾波放大電路，克服將記錄到的神經信號傳輸至信號處理端時所遇到的問題。

To understand the brain function, neural signal recording in awake animal is indispensable. Neuroprobe fabricated by MEMS process could possibly be used for chronic implantation, but the prerequisite is to reduce tissue damage to an acceptable level after long-term implantation. Therefore, evaluation of biocompatibility of different electrode materials is necessary at the very first step. We fabricate a silicon-substrate neuroprobe by using MEMS process. Three sensing microelectrodes, made of silver, gold, and platinum, are deposited on the neuroprobe tip. The purpose of using these materials for the microelectrode is for biocompatible evaluation. Parylene, a biocompatible polymer, was used to fully coat the probe to serve this purpose. The microelectrode was tested in vitro to obtain its electrical characteristics. This study brings up a novel fabrication procession to coat probe fully with parylene for increasing biocompatibility, and obtains the frequency response of the microelectrode impedance. Also, a head-stage circuit was developed to improve the quality of the transmission.