An Electrophysiological/Electrochemical Microelectrode for Electroencephalography and Adrenaline Sensing

Wearable and implantable microelectrodes are widely used to investigate brain function and treat neurological disorders. Here, we present a dual-function electrophysiological and electrochemical (EC) microelectrode composed of Cu-doped graphene nanosheets. The graphene nanosheets were vertically grown via chemical vapor deposition (CVD) and possess excellent electrical properties while exhibiting enhanced electrochemical (EC) activity due to the in situ-doped Cu. An electroencephalography (EEG) headband for humans, adrenaline (Adr) measurement device, and indwelling needle cores were successfully assembled using these graphene microelectrodes. The results of in vivo rat experiments revealed that the Cu-vertical graphene (VG) microelectrodes can accurately record intracranial electrocorticogram signals. Moreover, the EC signals could be used to test Adr levels at concentrations ranging from 0.5 to 800 μM at a pH range of 5-9.0, with detection limits within 0.024-0.112 μM. In human trials, the microelectrodes can recognize differences between EEG signals arising from the left and right frontal lobes and quickly respond to Adr levels in bodily fluids. Furthermore, when the left or right arms of the volunteers were raised, the scalp EEG signals for the left and right frontal lobes could be differentiated. Therefore, Cu-VG microelectrodes are well suited for wearable and portable human-machine interface sensors for rapid monitoring of brain function and neurotransmitter levels in clinical and point-of-care settings. This study presents a reliable human-machine interface sensor that can be utilized to correlate EEG signals and neurotransmitter regulation.