Construction of a MEMS-style Miniaturized Chemical Analysis System for Blood Analysis

通过血气、血电解质模块和参考电极模块的堆叠，实现了一种针对血液分析系统的小型化分析系统（μTAS）。虽然在单片上实现这样的系统是困难的，但使用模块化结构可以很容易地实现具有各种功能的高度复杂的系统。特别的是，研究了微型Ag/AgCl参比电极的结构和工作模式，以提高其长期稳定性。通过用聚酰亚胺层保护银层并在使用过程中生长AgCl，实现了大约300小时的寿命，这是传统结构的大约2000倍。利用该元件可以构造一个液结参比电极。因此，K^+、Na^+和Cl^-以及pH的测定只能在该装置中独立进行。用微型参比电极测量离子选择电极的电势，并与宏观参比电极测量的电势进行了比较。测量值的偏差不超过几个mV。除此之外，氧电极和二氧化碳电极的响应也很明显。使用堆叠模块构建的系统可以对六名分析人员进行在线分析。除了开发传感模块外，还开发了用于液体输送的微泵。通过电化学作用产生或熄灭氢气泡，借助施加的压力输送液体。实际上，可以将样品溶液引入微流通道，并且可以改变泵送速率。

A miniaturized analysis system (μTAS) aiming for blood analysis system was realized by stacking modules for blood gases, blood electrolytes, and a reference electrode module. Although realization of such a system on a single chip is difficult, a highly sophisticated system with various functions can be realized easily using the modular structure.A peculiar point is that the structure and operational mode of the miniature Ag/AgCl reference electrode were studied to improve the long-term stability. By protecting the silver layer with a polyimide layer and growing AgCl during the use of the element, a lifetime of approximately 300 h was achieved, which was approximately 2000 times compared with that of a conventional structure. A liquid-junction reference electrode could be constructed using the element. As a result, determination of K^+, Na^+, and Cl^- as well as pH could be made independently only in this device. The potentials of the ion-selective electrodes measured with the miniature reference electrode were compared with those measured with a macroscopic reference electrode. The deviation of the measured values was at most several mV. In addition to this, distinct responses were observed with the oxygen electrode and the carbon dioxide electrode. An on-line style analysis for six analysts could be performed with a system constructed with the stacked modules.In addition to the development of the sensing modules, a micropump for liquid transport was developed. A hydrogen bubble was generated or extinguished electrochemically and liquid could be transported with the help of the exserted pressure. A sample solution could actually be introduced into a microflow channel and the pumping rate could be changed.