Electrochemical characterization of multi-walled carbon nanotube coated electrodes for biological applications

Abstract

Carbon nanotubes, if used as a coating film on a conductive substrate, can substantially raise the charge storage capacity and lower the impedance of electrodes without significant increases to the geometric area. This is especially interesting in the case of stimulation of nervous tissue. We design implantable electrodes targeted at wide frequency stimulation of deep brain structures. Here we report on results in vitro with multi-walled carbon nanotubes coatings applied onto stainless steel substrates using direct current electrophoresis. We experimentally demonstrate, through electrochemical techniques such as cyclic voltammetry and impedance spectroscopy, the enhanced performance of multi-walled carbon nanotube (MWCNT) coatings for implantable electrodes by contrasting our experimental results against the more traditional stainless steel substrate characteristics. We also investigate surface morphology of aged electrodes. The interest in aged electrodes is dual fold: implantable electrodes have to be mechanically stable and present high shelf life. On the other hand, chemical modifications of the surface should be characterized. The effect of superficial oxygen adsorption on the aged MWCNT electrodes is observed through a modified cyclic voltammetric spectrum, but not through any changes in impedance spectroscopy.