ABSTRACT
Electrochemical analysis is usually conducted by inserting necessary electrodes into an electrolyte solution and by measuring changes in current or potential using an appropriate instrument. However, depending on the cases, it will be more beneficial if the analysis can be conducted with very small volume of solutions or outside the laboratory. A very promising feature of electrochemical devices is that miniaturization, batch-fabrication, and integration of components can easily be realized,1 which is not easily be realized on other devices such as optical devices. In addition, with a wealth of knowledge of electrochemistry, highly sensitive detection can
be expected. Moreover, electrochemistry can be used for other purposes such as microfluidic transport and regulation of pH in microfabricated flow channels and containers. In this chapter, basic techniques to realize such sophisticated electrochemical microdevices will be introduced. 27.1 Fabrication of Electrochemical
Electrode systems used in electroanalysis can be formed in the form of patterns of metals by a thin-film or thick-film process. Sputtering or vacuum evaporation is commonly used to deposit uniform layers of metals. To form the electrode patterns, a layer of photoresist coated on the metal layer is exposed to UV light and is developed to create patterns for electrodes. The pattern is used as a protective mask against wet-or dry etching of metals. After the etching and removal of photoresist, the electrodes with designed dimensions are obtained. The processes have a resolution of the order of a several micrometers. For smaller electrodes, electronbeam lithography is used. To delineate the active area of the electrode, silicon nitride, silicon dioxide, and polyimide are often used. Photoresists are also used when the damage to the layer is not anticipated.
