DYNAMIC ANALYSIS OF MULTI-WALLED CARBON NANOTUBES BASED MASS SENSORS FOR VARIOUS VIRUSES

Abstract

Carbon nanotubes (CNTs) are the most promising material for the application of Nanoelectromechanical resonators (NEMS) due to their high stiffness and light weight. These nanotubes are stronger than steel and almost half denser then aluminum. Carbon nanotubes are expected to have potential application in the field of biology, biomedical, electrical, electronics and advanced nano-composites as reinforcing material, where they may be utilized as bio sensors, transistors, resonators and interconnects. An attempt is made through this work to investigate the suitability and sensitivity of multiwalled carbon nanotubes (MWCNTS) as a mass sensors and bio sensors. A continuum structural mechanics and molecular structural mechanics approaches are utilized to model the MWCNTs and dynamic analysis is carried out using finite element method (FEM) in Abaqus. A significant frequency shift is observed during dynamic analysis of MWCNTs. Multi-walled carbon nanotubes with different aspect ratios are utilized and it is observed that, smaller is the aspect ratio higher is the frequency shift or in other words short nanotubes are more sensitive to mass than longer MWCNTs. The effect of the position of the mass along the length of the nanotubes, its magnitude and different boundary configuration is reported in present work. Cantilevered MWCNTs of different aspect ratios are utilized for simulating its behavior owing to the attached bacterium/virus at their free end. It is observed from the simulation results that, a significant frequency shift occurs due to the mass of viruses attached at free end of MWCNTs, which explore the potential of MWCNTs as bio sensors. It is also observed that resonant frequency of bridged MWCNTs is higher than cantilevered one, because of higher structural rigidity of nanotubes in bridged configuration. The effect of position of mass along the length of MWCNTs also investigated and observed that nearer the mass to free end higher is the resonant frequency shift in cantilevered MWCNTs. At the free end of MWCNT a mass of IO 25kg magnitude can detect clearly. Hence the sensitivity of MWCNT reaches upto 102kg (10 4Zg). The FEM simulation results obtained in present work are compared with analytical results to validate the model of MWCNTs and it is found that the FEM simulation results are in close proximity with analytical results. Additionally, the influence of the number of different atomic vacancy defects on the natural frequency of single-walled carbon nanotubes is observed using molecular structural mechanics approach in this work. Also effect of the position of the defect along the length of SWCNT is examined. It is observed that any type of defect hamper the stiffness of nanotubes cause decrease in natural frequency, but in certain cases structural mass loss owing to atomic vacancy defect dominate over the stiffhess reduction and hence natural frequency rises.