Experimental Study on Electrochemical Etching of Multi-Stepped Cylindrical Microelectrode with High Rotary Accuracy

Background: Microelectrodes have been widely used in the fields of microfabrication, measurement and medical applications. Electrochemical etching machining is a better method for fabricating microelectrode, and the multi-stepped electrode is easily fabricated to very small size. However, the rotary accuracy of multi-stepped electrode fabricated by conventional electrochemical etching is not high, because of the installation error of electrode and the uneven machining gap between the electrode and tool cathode. Various relevant papers and patents have studied different methods to improve the machining accuracy and efficiency of electrodes. Objective: In order to achieve the high-efficiency machining of multi-stepped cylindrical microelectrode with high rotary accuracy, a new electrochemical etching process (rotating electrochemical etching) is introduced. Methods: Firstly, the effect of machining current on the change of electrode diameter was deduced based on the principle of electrochemical etching. Secondly, the experiments proved that the rotation can improve the current change rate and the effective initial current and thus improve the machining efficiency. Following this, the influence of rotation on the rotary accuracy of electrode was analyzed, and the efficient method, which uses different rotation speeds combination, was proposed to fabricate multi-stepped cylindrical microelectrodes with high rotary accuracy. Thirdly, the influence of machining parameters such as the rotation speed, the voltage and the cut-off current, on the shape and size of electrode was analyzed. Results: Finally, a set of three-stepped cylindrical microelectrodes, which have the terminal diameter of less than 15μm and coaxial error within 1μm, was successfully fabricated using the optimized machining parameters. Compared with the conventional electrochemical etching process, the machining efficiency improved significantly. Conclusion: It has been proved that rotating electrochemical etching is a better method to improve the machining efficiency and rotary accuracy of microelectrodes.