Characterization of impedance properties of metal dry bioelectrodes with surface microstructure arrays

A metal dry bioelectrode with surface microstructure arrays is fabricated using the laser direct micromilling technology with advantages of high efficiency and low cost. The impedance properties of the metal dry bioelectrode are then analyzed using the two-electrode measurement method. The equivalent circuit of the electrode-skin contact model has been developed, and the influences of current frequency, electrode size, laser power and contact pressure on the impedance properties are investigated. The results show that the impedance of the bioelectrode decreases with increasing electrode diameter in the range of 6-10 mm. With increasing laser power, the impedance of the bioelectrode tends to decrease gradually. When a contact pressure is applied on the bioelectrode surface, its impedance drastically decreases. Compared with the traditional silver/silver chloride (Ag/AgCl) electrode, the impedance of the bioelectrode shows good stability. Due to the advantages of convenient, repeatable use, without the removal of the stratum corneum (the outermost layer of the skin), the developed metal dry bioelectrode has broad prospects in the collection and application of bioelectrical signals.