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標題: 可量測微升液體pH值與溶氧濃度的電化學式微流體感測晶片
Microfluidic Electrochemical Sensing Chips Capable of Measuring pH Value and Dissolved Oxygen Concentration of Microliter-Scaled Solutions
作者: 林孝安
Shiau-An Lin
Chien-Jen Wang
Ming-Jay Lin
Ching-Chou Wu
關鍵字: 氧化銥;微通道鹽橋;pH感測器;溶氧感測器;微流體晶片;Iridium oxide;salt-bridge microchannel;pH sensor;dissolved oxygen sensor;microfluidic chip
出版社: 臺中巿: 國立中興大學農學院
Project: 農林學報, Volume 62, Issue 4, Page(s) 331-341.
近年來利用微製程製作的微流體生物感測器已受到廣泛重視,可藉由量測微量液體的溶氧濃度(dissolved oxygen concentration, [O_2])與pH值的變化,以得知生物體的呼吸活性與酸化率。研究中藉由定電流法沈積氧化銥(IrOx)薄膜於金電極上,用以當作電化學量測系統的參考電極與pH 感測電極,以建構一全晶片式電化學感測器。以0.6~1.0 mA/cm^2電流密度(current density, CD)沈積之IrOx電極的pH靈敏度與鍍層厚度並無顯著差異,但IrO_x鍍層厚度隨沈積時間的增加而變厚。且比較以0.8 mA/cm^2沈積5分鐘(0.8CD/5M-),10分鐘(0.8CD/10M-)與15分鐘沈積(0.8CD/15M-deposited)之IrO_x-pH電極的90%反應時間(RT_90),顯示IrO_x膜愈薄其RT_90愈短。但在長期穩定度上以0.8CD/15M-deposited IrO_x電極的電位漂移量最小,僅為0.33±0.12 mV/h。藉由整合晶片上的IrO_x參考電極與利用微通道鹽橋對量測槽的連結,可對微量液體同時量測[O2]與pH值,在交互量測0 mM [O_2]的100 mM Na_2SO_3(pH 8.0)與0.21 mM [O_2]之10 mM PBS (pH 7.0)溶液,其相對於[O_2]之還原電流變化值為42.85±0.84 nA(relative standard deviation(RSD): 2.0%)與相對於pH值之開迴路電位變化值為81.98±2.19 mV(RSD: 2.7%),此微小的RSD顯示該晶片對[O_2]與pH值量測具有良好重覆性。此整合電化學感測器之微流體晶片未來可用於量化藥物對細胞活性的影響,可增加藥物試驗的速度與減少成本的花費。

Recently, the microfluidic biosensing chips fabricated by microfabrication techniques have attracted wide interests. The chips can measure the change in the dissolved oxygen concentration ([O_2]) and the pH values of solutions so as to estimate the respiration activity and acidification rate of cells. In this study, the Au electrodes galvanostatically electrodeposited by an iridium oxide (IrO_x) layer were used as the reference electrode of electrochemical measuring system and the pH indicator to construct a whole chip-type electrochemical sensor. The IrO_x-deposited electrodes by using the 0.6~1.0 mA/cm^2 current density (CD) didn't present significant change in the sensitivity of sensors and the thickness of IrO_x layer. Furthermore, the 90% response time (RT_(90)) of IrO_x electrodes deposited by the 0.8 mA/cm^2 CD for 5, 10 and 15 min (designated as 0.8CD/5M-, 0.8CD/10M and 0.8CD/15M-deposited electrode) was compared to show that the thinner IrO_x film had the shorter RT_(90). However, the 0.8CD/15M-depostied IrO_x electrodes exhibited the smallest potential drift of 0.33±0.12 mV/h in the long-term stability test. With the utilization of on-chip IrO_x reference electrode and the salt-bridge microchannel connecting the measuring chamber, the chip can simultaneously measure [O_2] and pH values. The change in the reductive current corresponding to [O_2] and the open circuit potential (OCP) corresponding to pH was respectively 42.85±0.84 nA (relative standard deviation (RSD): 2.0%) and 81.98±2.19 mV (RSD: 2.7%) when alternately injecting 100 mM Na_2SO_3 (pH 8.0 and 0 mM [O_2]) and 10 mM PBS (pH 7.0 and 0.21 mM [O_2]) in the measuring chamber of microfluidic chip. The small RSD implies that the chip possesses good repeatability for the measurement of [O_2] and pH. The microfluidic chip integrating the electrochemical sensors can be used to quantify the effect of drugs on the cellular physiological behavior, resulting in promoting the progress of drug tests and reducing the measuring cost.
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