Fabrication and Characterization of a Multiwall Carbon Nanotube Needle Biosensor

A nanotube electronic needle biosensor was developed to provide fast, low cost, accurate detection of biomolecules. The sensor was formed by synthesizing highly aligned multi-wall carbon nanotube arrays. Nanotube bundles from the array were welded onto the tips of tungsten needles using a microscope. The needles were then encased in glass and a polymer coating. Cyclic voltammetry (CV) for the respective reduction of 6 mM K3Fe(CN)6in a 1.0 M KNO3was performed to examine the redox behavior of the nanotube needle. The CV results showed a steady-state response attributable to radial diffusion with a high steady-state current density. An amperometric sensor was then developed for glucose detection by physical attachment of glucose oxidase on the nanotube needle. A label-free immunosensor based on electrochemical impedance spectroscopy was also formed. The nanotube needle amperometric have good sensitivity with a low detection limit, and the possibility exists to keep decreasing the size of the needle to increase the sensitivity.