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

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Abstract

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/cm2 and the interface capacitance of electrodes to 3.0 × 104 μF/cm2 for the geometric area, compared with 4.6 mC/cm2 and 443.1 μF/cm2, respectively, for the smooth Pt–Ir electrode. The corresponding optimal results for the optically measured area are 111.8 mC/cm2 and 2.6 × 104 μF/cm2, 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.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Nos. 51777115 and 81527901), the National Key Research and Development Program of China (Nos. 2016YFC0105502 and 2016YFC0105900), Tsinghua University Initiative Scientific Research Program and Major Achievements Transformation Project of Beijing’s College.

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Authors and Affiliations

  1. National Engineering Laboratory for Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084, China

    Linze Li, Changqing Jiang & Luming Li

  2. Precision Medicine and Healthcare Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, 518071, China

    Luming Li

  3. IDG/McGovern Institute for Brain Research at Tsinghua University, Beijing, 100084, China

    Luming Li

  4. Institute of Epilepsy, Beijing Institute for Brain Disorders, Beijing, 100093, China

    Luming Li

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  1. Linze Li
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  2. Changqing Jiang
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  3. Luming Li
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Conceptualization, all authors; Methodology, LZL and CQJ; Investigation, LZL; Writing-original draft, LZL; Writing-review & editing, all authors; Funding acquisition, CQJ and LML; Supervision, CQJ and LML.

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Correspondence to Changqing Jiang or Luming Li.

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Li, L., Jiang, C. & Li, L. Hierarchical platinum–iridium neural electrodes structured by femtosecond laser for superwicking interface and superior charge storage capacity. Bio-des. Manuf. 5, 163–173 (2022). https://doi.org/10.1007/s42242-021-00160-5

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