An integrated three-electrode system with a micromachined liquid-junction Ag/AgCl reference electrode

Abstract

A micromachined liquid-junction Ag/AgCl reference electrode was employed to fabricate an integrated three-electrode system. The reference electrode features a durable thin-film Ag/AgCl element whose entire surface was coated with a hydrophobic membrane and AgCl layer grown from its periphery. On the other side of the chip were formed a platinum working electrode and a platinum counter electrode. The cleanliness of the thin-film platinum working electrode was satisfactory to conduct electrochemical analyses including cyclic voltammetry. No substantial difference was observed in the cyclic voltammograms between the integrated system and the macroscopic three-electrode system in terms of their peak current and half-wave potential. The integrated electrode system was also applied to fabricate one-chip bio/chemical sensors. The miniature glucose sensor showed a distinct response against step changes of glucose concentration. The one-chip hydrogen electrode was used to conduct potentiometric titration. A good coincidence was again confirmed between the integrated system and the macroscopic system.