Flexible silk-fibroin-based microelectrode arrays for high-resolution neural recording

High-precision neural recording plays a pivotal role in unraveling the intricate mechanisms that underlie information transmission of the nervous system, raising increasing interest in the development of implantable microelectrode arrays (MEAs). The challenge lies in providing a truly soft, highly conductive and low-impedance neural interface for precise recording of the electrophysiological signals of individual neurons or neural networks. Herein, by implementing a novel topological regulation strategy of silk fibroin (SF) crosslinking, we prepared a flexible, hydrophilic, and biocompatible MEA substrate, facilitating a biocompatible neural interface that minimizes mechanical mismatch with biological tissues. Additionally, we established a strategy involving screen-printing combined with post-coating to prepare MEAs with high conductivity, low impedance and high capacitance, by coating PEDOT:PSS on titanium carbide (Ti₃C₂) microarrays. The Ti₃C₂ nanosheets, as the conductive track of the MEAs, avoided the charge drifting associated with metals and facilitated the processing of the MEAs. Further coating PEDOT:PSS on the electrode points reduced the impedance 100-fold, from 10⁵ to 10³ Ω. Experimental validation confirmed the superior electrophysiological signal recording capabilities of the SF-based MEA (SMEA) in peripheral and cerebral nerves with a much higher signal-to-noise ratio (SNR) of 20. In particular, we achieved high-precision recording of the action potential (AP) induced by flash visual stimulation, demonstrating high performance in weak signal recording. In summary, the development of SMEA provides a robust foundation for future investigations into the mechanisms and principles of neural circuit information transmission in complex nervous systems.