Carbon Nanotube Array‐Based Flexible Multifunctional Electrodes to Record Electrophysiology and Ions on the Cerebral Cortex in Real Time

Abstract Electrophysiology and neurochemicals such as Ca²⁺, K⁺, and Na⁺ on the cerebral cortex can synergistically reflect the neurophysiological states. Transparent electrodes have been reported to record electrocorticography (ECoG) and image Ca²⁺ on the cerebral cortex surface. However, Ca²⁺ imaging is unable to track extracellular changes correlated with neural activities such as anesthesia, and imaging techniques to monitor K⁺ and Na⁺ are yet unavailable. Here, a flexible multifunctional electrode (FME) based on carbon nanotube array is presented to record ECoG and extracellular ions of Ca²⁺, K⁺, and Na⁺. The FME exhibits both lower impedance and higher capacitance than that of conventional gold electrodes. It simultaneously shows stable ion‐sensing performance and long‐term biocompatibility. The FME realizes multi‐model recording of ECoG and extracellular ions on the cerebral cortex surface of rats, providing an effective detection method for brain science.