A fully microfabricated coplanar single-walled carbon nanotube three-electrode system for biosensors

A co-planar single walled carbon nanotube (SWCNT) electrode system with all electrodes (working, counter and reference) was fully microfabricated on a glass substrate. The process is based on: (a) a standard microfabrication process to define the conducting tracks and a nitride passivation, (b) a transfer printing of SWCNT film, and (c) a chlorination process of thin-film Ag to form AgCl reference electrode. This three electrode device exhibits clear electrochemistry both under voltammetric and amperometric conditions and is thus a candidate for all electrochemical biosensors. An amperometric glucose biosensor based on this electrode system has been prepared by immobilizing glucose oxidase (GOx) on well defined SWCNT working electrodes. The glucose biosensor shows a linear relationship between current response and glucose concentrations from 0.5 to 10 mM/L; the sensitivity is 30 (uA/cm²)/(mol/L).