Electrochemically gold-modified carbon nanotube fibers for neural sensing

Flexible carbon nanotube fiber-based neural electrodes offer significant advantages for neural interface applications; however, their practical implementation is limited by relatively low electrical conductivity, insufficient mechanical strength, and challenges in implantation. In this study, we present a synergistic strategy to address these inherent challenges through structural densification combined with metal nanoparticle integration. Continuous CNTF ribbons were fabricated by the floating chemical vapor deposition method and subsequently transformed into twisted fibers (T-CNTF) to reduce inter-tube voids and examine the mechanical response. Gold nanoparticles (Au NPs) were then electrochemically deposited onto the surfaces of T-CNTF, yielding metal-enhanced fibers (T-CNTF-Au) with improved electrical conductivity, achieving a maximum value of 2.90 × 10 5 S/m at a nominal Au deposition thickness of 100 nm. A systematic investigation demonstrated a strong structure–property relationship, where a sample prepared at a nominal Au deposition thickness of 50 nm increased fracture elongation to approximately 28%. The fabricated electrode maintained electrical continuity during 5000 bending cycles with relative resistance change below 11%. Electrochemical impedance spectroscopy and cyclic voltammetry revealed mixed capacitive-resistance interfacial behavior and repeatable voltammetric response across cycles 22–25, during which cathodic charge-storage capacity declined from approximately 95.5 to 81 mC cm⁻ 2 . The optimized fibers were integrated into multi-channel neural electrode arrays and implanted into the hippocampal region of mice using stereotaxic techniques. Electrophysiological recordings were acquired over a 2-h acute session, from which a continuous 41.7-min epoch was quantitatively analyzed using four validated contacts. The resulting median impedance magnitude at 1 kHz, spike-free RMS noise, negative-event amplitude, and signal-to-noise ratio were 13.13 kΩ, 6.45 μV, 45.97 μV, and 6.86 (16.73 dB), respectively. Overall, this study demonstrates that metal-enhanced CNTF electrodes, combining high electrical conductivity with mechanical flexibility, constitute a promising platform for next-generation neural interfaces. The proposed approach provides valuable insights into the rational design of high-performance, flexible neural electrodes for advanced neuroscience applications.