Microfluidic integrated multi-walled carbon nanotube (MWCNT) sensor for electrochemical nucleic acid concentration measurement

A microfluidic assisted electrochemical (EC) biosensing platform based on vertically aligned multi-walled carbon nanotubes (MWCNTs) embedded in SiO2 was developed using multi-scale manufacturing techniques. The MWCNT-EC sensor was fabricated using electron beam (E-beam) nanolithography, thin-film metal deposition and reactive/electrochemical etching. The MWCNT-EC sensor was integrated with a microfluidic EC cartridge including the counter and reference electrodes and a PDMS microfluidic channel on a glass substrate. After packaging the MWCNT chip and microfluidic EC cartridge into a manifold which included sample inlet/outlet, electrical connectors and a miniaturized potentiostat, the platform was characterized with differential pulse voltammetry (DPV) using ferrocyanide and ruthenium(II) solutions. The DPV measurement results are consistent with commercial EC systems. Microfluidic nucleic acid hybridization was demonstrated using the MWCNT chip on which the MWCNT tips were functionalized with single stranded DNA (ssDNA) probes. The synthetic complementary ssDNA targets were input through the microfluidic channel and hybridized with the functionalized ssDNA probes. The relative DPV peak magnitude linearly correlated with the target DNA concentration. This platform provides a simple way to integrate a MWCNT biosensor with microfluidics as an electronic system for a variety of possible nucleic acid analyses.