Batch Fabrication of Miniaturized Ag/AgCl Reference Electrode With Ion Exchanging Micro-Nano-Pores by Silicon-Base Double-Side Anisotropic Etching Process

To address the demands for the large-scale application of electrochemical sensors in the field of environmental pollution monitoring, a novel silicon-based Ag/AgCl reference electrode (RE) was batch fabricated. The reference electrode consisted of a mini-chamber for saturated KCl solution storage and micro-nano-pores for Cl
^-
exchange. The microstructures were fabricated via a two-step KOH wet etching on double sided oxidized and polished silicon wafer. The size of the micro-nano-pore diameters were precisely controlled by the etching time. The Ag/AgCl electrode was prepared on a Pyrex 7740 glass via silver lift-off process and electrochemical treatment. The silicon and glass substrates were joined by anodic bonding to form the finished Ag/AgCl micro- reference electrode. Compared with a commercial glass tube Ag/AgCl reference electrode, the micro-RE had the advantages of better reference potential stability, a small size, easy integration, and batch fabrication. The micro-RE was combined with a PbO
₂
working electrode and a Pt counter electrode and applied to measure the glucose concentration in water samples. The results indicate that the novel micro-RE suitable for actual electrochemical detection, such as chemical oxygen demand (COD) measurements in water samples.