Dynamic Liquid Membrane Electrochemical Modification of Carbon Nanotube Fiber for Electrochemical Microfabrication

Carbon nanotube fibers (CNFs) are a promising material for use as lightweight, high-strength, electrically conducting tool cathodes in wire electrochemical micromachining (WECMM) in which a high-performance tool cathode is crucial for optimal processing performance. However, the outstanding advantages of pristine CNFs, such as fiber strength, electrical conductivity, and hydrophilic surface, have so far remained underutilized as tool cathodes in WECMM. Herein, electrochemical modification using a dynamic liquid membrane is proposed as an effective online method for functionalizing CNFs prior to WECMM. The proposed method not only improves the assembly accuracy and efficiency but also avoids unnecessary damage to the modified CNF during installation. The introduced functional groups (-OH and -COOH) effectively improved the electrical conductivity and hydrophilicity of CNFs. The influences of H₂O₂ concentration, applied voltage, and anodization time on the surface modification process were examined experimentally. The use of a pulsed voltage was further proposed to prevent the loss of fiber strength due to over-anodization. Finally, the use of modified CNF electrodes with good surface morphology, strength, and conductivity in WECMM was demonstrated to afford superior machining stability, efficiency, and accuracy as well as improved surface quality compared with the conventional tool cathodes.