High-density, Ultraflexible Organic Electrochemical Transistor Array for Brain Activity Mapping

Organic electrochemical transistors (OECTs) emerge as promising neural electrodes owing to their superb biocompatibility, flexibility, on-site signal amplification capabilities, low operating voltage, and performance stability in aqueous conditions. Traditional implementations of OECT arrays have been limited by their relatively low channel count, large footprint, slow response time, and inadequate spatiotemporal resolution. Here, we report scalable high-density OECT arrays designed for high-reolution mapping of electrocorticogram signals. Our design features vertically stacked source and drain electrodes, achieving an array configuration with 1,024 channels at a density of 10,000 transistors per square centimeter and an average peak transconductance of 3.32 mS. For prototype demonstration, we apply a 64-channel array for the mapping of epileptic signals in mice, yielding a signal-to-noise ratio (SNR) of 32 dB, which significantly surpasses that of traditional platinum electrodes. The ultraflexible OECT array, featuring a total thickness of 4.2 µm, demonstrates high mechanical compliance, biocompatibility, and long-term stability, remaining effective for over three months post-implantation. This high-resolution, ultraflexible OECT array offers potential to precisely monitor neural activities across extensive brain areas, essential for both research and clinical applications.