Ultrasensitive monolithic dopamine microsensors employing vertically aligned carbon nanofibers

Abstract Brain-on-Chip devices, which enable on-chip cultures of neurons to simulate brain functions, are receiving tremendous attention to meet the demands of both fundamental research and clinical trials. Thus, miniaturized sensors are being developed to accomplish real-time monitoring of neurotransmitters, which are the signaling molecules between neurons and benchmarks for neuron network operation. Electrochemical sensors are promising candidates for detecting a critical neurotransmitter, dopamine (DA), a biomarker for Parkinson’s disease. A key advantage of electrochemical sensors is their capability of fast, real-time recording. However, current state-of-the-art electrochemical DA sensors are suffering from various issues like limited sensitivity and cumbersome fabrication. Here, we report a novel route in monolithically microfabricating vertically aligned carbon nanofiber (VACNF) electrochemical DA microsensors by an anti-blistering slow cooling process. Thanks to the new microfabrication process, we are able to achieve VACNF microsensors with complete insulation and large surface areas. The champion device shows extremely high sensitivity of 4.52×104 μA/μM · cm2, which is at least two-orders-of-magnitude higher than current devices, and a highly competitive limit of detection of 0.243 nM. These figures of merit will open new windows for future applications of Brain-on-Chip devices such as electrochemical recording from a single neuron.