High-density, ultraflexible organic electrochemical transistor array for brain activity mapping

Organic electrochemical transistors (OECTs) are emerging as promising neural electrodes due to their capabilities for on-site signal amplification, customizable mechanical flexibility, biocompatibility, and stability in biotic conditions. However, documented flexible OECT arrays face limitations in channel count and spatiotemporal resolution. Here, we report a high-density, ultraflexible OECT array designed explicitly for the high-resolution electrocorticogram (ECoG) signal recording. Featuring vertically stacked source and drain electrodes, the array incorporates 1024 channels in a compact form factor, only 4.2 μm thick, achieving a density of 10 000 transistors per square centimeter. A 16 × 16 segment of the 1024-channel array was utilized to map whisker-related signals in a mouse model, effectively locating neural activities in response to tactile stimulation. Besides, it demonstrates high mechanical compliance and long-term stability, remaining effective for three months post-implantation and beyond. With its excellent resolution and durability, the ultraflexible OECT array promises to enhance the monitoring and understanding of neural dynamics across a wide spatiotemporal scale.