Fabrication of slow leak miniaturized Ag/AgCl reference electrodes

The miniaturization of electrochemical sensors for environmental and biomedical applications has drawn significant interest recently. However, size and drifting of the reference electrodes (REs) have always been challenged to develop miniaturized sensor with longer lifetime. Critically, the electrolyte mixture of the RE affects its lifetime. Therefore, most of the REs contains saturated electrolyte concentration for stable ion-exchange across thejunction. Nevertheless, utilisation ofthe saturated electrolyte makes it unsuitable fortestingin low concentration solutions. Thus, a novel process is developed to fabricate slow leak miniaturized Ag/AgCl reference electrodes containinglow concentration electrolyte with strong ionic andpH stability. A Teflon tube with 4 mm outer diameter and 10 mm height containing electrolyte mixture of Agarose in potassium chloride (KC1) were developed to identify the stability and rep eatability o f electrode motive force (EMF in mV) by storing it in 0.1 mM KC1 (low-concentrationtest solution) for 15 days. The ionic stability is validated usingKCl solutions with concentration change from0.01 mMto 1 M, and pH stability is confirmed using sodium phosphate buffer solution with various pH levels.