Carbon nanotube fiber electrodes modified with surface-arrayed nanowires for enhanced mass transport in electrochemical nanofabrication

Carbon nanotube fiber (CNF) is a promising wire electrode material for wire electrochemical micromachining due to its high strength, electrical conductivity, and corrosion resistance. However, the smooth and hydrophobic surface of pristine CNF promotes bubble adhesion and interfacial velocity slip, which severely restricts mass transport and degrades machining stability. In this study, a surface-arrayed nanowire-modified carbon nanotube fiber electrode is proposed to enhance mass transport during micromachining. Vertically aligned NiCo₂S₄ nanowires, with an average height of approximately 10 μm, were grown in situ on the fiber surface, resulting in a surface that is both microtextured and functionalized. The nanowire array effectively penetrates the gas cushion, suppresses boundary velocity slip, and strengthens fluid-solid coupling. Flow field simulations and theoretical analysis demonstrate intensified near-wall convection and improved mass transport induced by the microtextured surface. Wire electrochemical micromachining experiments on Ni-based metallic glass show that the modified electrode significantly improves machining performance. The maximum stable feed rate was increased to 0.8 μm/s, the power fluctuation frequency was reduced from 2.2/min to 0.2/min, and the surface roughness R a was decreased by approximately 60% to 25.5 nm. In addition, high-precision batch fabrication of 25 stepped cantilever micro-components was successfully achieved using the multiwire and multilayer electrochemical machining with a relative standard deviation below 0.1%, demonstrating the engineering applicability of the proposed electrode. This work provides a practical approach for overcoming mass transport limitations in wire electrochemical micromachining through electrode surface microstructure engineering.