Mercury-plated iridium-based microelectrode arrays for trace metal detection

Trace metals are one of the important components of a marine ecosystem, and their biogeochemical cycles are important for understanding the structure and function of such ecosystems. In this paper, recessed mercury-plated iridium-based microelectrode array sensors are developed for the in-situ detection of trace metals in the ocean. Using COMSOL Multiphysics as a tool simulation and by changing the diffusion layer thickness, the electrode size, and the electrode spacing, we clarified the changes in different types of electrode arrays and determined the exact range of the parameters of the microelectrode array that can avoid the shielding effect. Based on the simulation results, four different parameters of the microelectrode array were successfully fabricated. A scanning electron microscope (SEM) was used to observe the geometry and surface morphology of the microelectrode array. An atomic force microscope (AFM) was used to observe the etched morphology and surface roughness of the microelectrode. The results show that the microelectrode processing technology can meet the production requirements. A cyclic voltammetry test was performed in 1 mmol/L K3Fe(CN)6. The results show that the diffusion layer thickness is greater than the electrode radius, and the electrode can be considered a microelectrode with a radial diffusion characteristic. Thus, the proposed microelectrode array can be used to detect metals. The accuracy of the simulation is verified by comparing the simulation with the test results. The simulation results can be used to guide the design of microelectrode arrays and the selection of test conditions.