Electrochemical principles provide a means to achieve highly sensitive detection. However, depending on the target analyte, further improvements in the detection limit and sensitivity are necessary. To this end, microelectrodes are indispensable. Detection using microelectrodes offers the advantages of enhanced mass transport and low background currents, which can effectively enhance the Faradaic currents originating from redox reactions of target analytes relative to the background currents. As the currents generated from single microelectrodes are small, arrays of microelectrodes are typically employed to increase the current output while preserving the microelectrode properties. The advantageous properties of microelectrodes render them useful in voltammetry and coulometry. The detection limit and sensitivity of coulometry can be improved further by measuring the amount of silver deposited on a microelectrode array via coupling during the oxidation of the analyte on the other connected microelectrode array. Redox cycling is effective for current signal amplification. In redox cycling, microelectrode arrays of various geometries such as interdigitated electrodes, nanogap electrodes, and ring-disk electrodes are used. By placing two sets of closely spaced microelectrodes for oxidation and reduction, the reaction products can be effectively regenerated and reused, thereby significantly increasing the current. In addition, nanomaterials such as gold nanoparticles and carbon nanotubes are often used to improve the detection performance. In particular, to detect nucleic acids, there exist various specific techniques that fully utilize the advantageous properties of nucleic acids for signal amplification.