Neural stimulation/recording microelectrodes have been widely used to investigate neural activities and regulate neural disorders. In recent years, smaller and more sophisticated microelectrode arrays that are capable of precise stimulation/recording for neuronal networks have attracted great attention, which requires the dramatic decrement of geometric area.

For precise neural recording or stimulation purposes, high cathodic charge storage capacity (CSC_c), low electrical impedance and the safe charge injection capability (CIC), as well as the biocompatibility, are considered critical to reduce power consumption and ensure safe, effective neural signal transport.

Professor WU Tianzhun from Shenzhen Institute of Advanced Technology of Chinese Academy of Sciences, collaborating with colleagues, recently developed a high performance iridium oxide (IrO_x)/platinum (Pt) nanocones, which is considered to be a novel composite coating to fulfill the critical stability and low power consumption requirements for active implant such as the artificial retina. The paper was published in Electrochimica Acta.

As an adhesion layer between Pt substrate and IrO_x layer, the 3D Pt nanocones were introduced and this 3D mid-layer was nanorough and nanoporous owning at least two benefits. The nanostructure's larger surface area accommodates more IrO_x mass in a less dense form and provides an intermediate layer for IrO_x deposition, and it promotes good adhesion to substrate besides.

The achieved IrO_x/Pt nanocones coated microelectrode has higher CSC_c and CIC for pulse stimulation. A typical microelectrode modified with nanostructured IrO_x/Pt nanocones coating has a low impedance down to 2.45 kW·cm² at 1 kHz, and a CSC_c up to 22.29 mC·cm^-2, which was about 6, 2.8 and 2.7 times higher than CSCc of those samples coated with bare Pt, Pt gray and IrO_x, respectively.

Furthermore, it demonstrated superior mechanical, electrochemical stability and CIC. This composite coatings with well-controlled nanostructure can be used in broader applications for high-performance stimulation or recording electrodes as well as neural prosthesis.

The preliminary results was also presented in IEEE international conference on Nano/Micro Engineered and Molecular Systems (NEMS 2017), and was awarded “Finalist of best conference poster award”.