Abstract
Traditional neural electrodes have been employed widely to investigate the physiological functions of the brain. However, various micro-electrode probes currently developed still cannot reliably detect the activity of the neural cell for a long term, and cannot stimulate the neural tissues regionally and selectively. This is mainly due to that the probe size is still too large, the impedance is too high for metallic electrodes at low frequency region, and the long time implantation will induce tissue inflammation. To resolve above issues, this research is to study carbon nanotubes (CNTs) as an neural electrode material to replace traditional neural electrodes. A novel cone-shaped 3D carbon nanotube (CNT) probe is proposed as an electrode for the applications in neural recording in this work. The electrode consists of CNTs synthesized on the cone-shaped Si (cs-Si) tip by catalytic thermal chemical vapor deposition (CVD). This probe exhibits a larger CNT surface area with the same footprint area and higher spatial resolution of neural recording compared to planar-type CNT electrodes. An approach of improving the CNT characteristics by H2O or O2 plasma treatment to modify the CNT surface will be also presented. In addition, the effect of microwave (MW) treatment to improve the adhesion of carbon nanotubes (CNTs) to a substrate is examined. According to electrochemical characterization, O2 plasma-treated 3D CNT (OT-CNT) probes revealed low impedance per unit area (~ 64.5 □□mm-2) at 1 kHz and high specific capacitance per unit area (~ 2.5 mF cm-2). Furthermore, the OT-CNT probes were employed to record the neural signals of a crayfish nerve cord. The findings in this work suggest that OT-CNT probes exhibit potential advantages of high spatial resolution and superb electrochemical properties which are suitable for neural recording applications.