Expanding Carbon Electrode Area and Drifting Reference Electrode Potential in Screen-Printed Electrode Strips

Screen-printed electrode (SPE) strips are widely used for electrochemical detection owing to their low cost, ease of fabrication, and suitability for point-of-care testing. Their electrochemical performance must remain reproducible across multiple uses, varied solution conditions, and extended measurement times; however, relevant studies are rare. In this study, we demonstrate that the electrochemical behavior of SPEs is significantly influenced by (i) dynamic changes in the real electrode area of carbon SPEs (working electrodes) and (ii) potential drifts in Ag SPEs (reference electrodes). The gradual wetting of pores in the carbon SPEs, which is affected by the solution composition and incubation time, increases the real electrode area and the non-Faradaic capacitive charging current. Notably, rapid wetting occurs in surfactant-containing and biological solutions. The wetting process also affects the Faradaic current of an electroactive species to a certain extent. Furthermore, the potential of Ag SPEs exhibits shifts with repeated use and under different incubation conditions, particularly in the presence of an electroactive species. These findings demonstrate that variations in the real electrode area and reference electrode potential play critical roles in SPE strip-based electrochemical measurements. Addressing these factors is essential for achieving accurate and reproducible results, particularly in repeated or long-term measurements, and in measurements involving surfactant-containing or biological solutions.