Hierarchical platinum–iridium neural electrodes structured by femtosecond laser for superwicking interface and superior charge storage capacity

The interfacial performance of implanted neural electrodes is crucial for stimulation safety and the recording quality of neuronal activity. This paper proposes a novel surface architecture and optimization strategy for the platinum–iridium (Pt–Ir) electrode to optimize electrochemical performance and wettability. A series of surface micro/nano structures were fabricated on Pt–Ir electrodes with different combinations of four adjustable laser-processing parameters. Subsequently, the electrodes were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and wetting behavior. The results show that electrode performance strongly depends on the surface morphology. Increasing scanning overlap along with moderate pulse energy and the right number of pulses leads to enriched surface micro/nano structures and improved electrode performance. It raises the maximum charge storage capacity to 128.2 mC/cm 2 and the interface capacitance of electrodes to 3.0 × 10 4 μF/cm 2 for the geometric area, compared with 4.6 mC/cm 2 and 443.1 μF/cm 2 , respectively, for the smooth Pt–Ir electrode. The corresponding optimal results for the optically measured area are 111.8 mC/cm 2 and 2.6 × 10 4 μF/cm 2 , which indicate the contribution of finer structures to the ablation profile. The hierarchical structures formed by the femtosecond laser dramatically enhanced the wettability of the electrode interface, giving it superwicking properties. A wicking speed of approximately 80 mm/s was reached. Our optimization strategy, leading to superior performance of the superwicking Pt–Ir interface, is promising for use in new neural electrodes.