Wafer-scale fabrication of patterned carbon nanofiber nanoelectrode arrays: A route for development of multiplexed, ultrasensitive disposable biosensors

One of the major limitations in the development of ultrasensitive electrochemical biosensors based on one-dimensional nanostructures is the difficulty involved with reliably fabricating nanoelectrode arrays (NEAs). In this work, we describe a simple, robust and scalable wafer-scale fabrication method to produce multiplexed biosensors. Each sensor chip consists of nine individually addressable arrays that uses electron beam patterned vertically aligned carbon nanofibers (VACNFs) as the sensing element. To ensure nanoelectrode behavior with higher sensitivity, VACNFs were precisely grown on 100 nm Ni dots with 1 μm spacing on each micro pad. Pretreatments by the combination of soaking in 1.0 M HNO3 and electrochemical etching in 1.0 M NaOH dramatically improved the electrode performance, indicated by the decrease of redox peak separation in cyclic voltammogram (ΔEp) to ∼100 mV and an approximately 200% increase in steady-state currents. The electrochemical detection of the hybridization of DNA targets from E. coli O157:H7 onto oligonucleotide probes were successfully demonstrated. The 9 arrays within the chip were divided into three groups with triplicate sensors for positive control, negative control and specific hybridization. The proposed method has the potential to be scaled up to N × N arrays with N up to 10, which is ideal for detecting a myriad of organisms. In addition, such sensors can be used as a generic platform for many electroanalysis applications.