15.7 Heterogeneous integrated CMOS-graphene sensor array for dopamine detection

Understanding dopamine (DA) signaling in the brain is essential for advancing our knowledge of pathological disorders such as drug addiction, Parkinson's disease, and schizophrenia. Currently, fast-scan cyclic voltammetry (FSCV) with carbon microfiber (CMF) electrodes is the method of choice in neuroscience labs for monitoring the concentration of phasic (transient) DA release. This method offers sub-second temporal resolution and high specificity because the signal of interest occurs at a known potential. However, existing CMF electrodes are bulky, limiting the spatial resolution to single-site measurements. Further, they are produced through manual processes (e.g. cutting CMFs under optical microscope), thus introducing significant device variability [1]. Lastly, when long probes (3-to-5cm) are used to monitor DA release in deep brain structures of large animals, environmental noise severely diminishes the detection limit [1]. To address these problems, we combine advances in nanofabrication with silicon chip manufacturing to create a heterogeneous integrated CMOS-graphene sensor for accurate measurement of DA with high spatiotemporal resolution (Fig. 15.7.1).