Investigation On The Vibration Of Carbon Nanotube Based Mass Sensors

As a new type of sensor, micro-nano-cantilever has received widely attention and investigation in physics, chemistry, biology and other fields in recent years. One of its goals is to continuously improve and make breakthroughs in treating the detection limit of the measured objects. With the reduction of the sensor size, especially the introduction and use of carbon nanotubes, different research teams are successfully detected single atoms mass by experiments in 2008. However, the key problem is how to determine the relationships between the attached mass and the amount of change of the intrinsic frequency shift.In the present study, we explore the potential of using single wall carbon nanotubes (SWCNTs) as nanomechanical resonators in nanosized mass sensors. It reveals the effect of adsorption mass on its intrinsic frequency drift. The main works of this study are as follows:Firstly, the adsorption properties of SWCNTs and molecular dynamics simulation method have been introduced. And LAMMPS (large-scale atomic/molecular massively parallel simulator) was employed in the simulation, the Lennard-Jones potential and the BREO potential were respectively used to characterize the long and short range atomic interactions of carbohydrate. The influence of adsorption molecular varies from 1 to 3 phenyl rings on resonant frequency of carbon nanotubes has been studied. The comparison between additional mass molecular dynamics simulation (AMMDs) and full-atom molecular dynamics simulation (FAMDs) indicated that for adsorption single phenyl of higher structural rigidity, frequency drift of carbon nanotubes depends on its mass.Secondly, considering the limitations of molecular dynamics simulation and engineering background of carbon nanotubes mass sensor, the Euler-Bernoulli beam model has been applied to study its vibration characteristics in this paper.. In order to figure out how the attached single molecular affects the resonant frequency of the carbon nanotube resonators, the resonators both in bridged and in cantilevered configurations are studied. The numerical simulation results indicate that in the condition of different boundary constraints and the specific adsorption location, the heavier attached mass and shorter carbon nanotube is, the greater frequency drift will be. The numerical simulation results indicate that in the condition of specific adsorption location on above-mentioned boundary constraints, the heavier attached mass and shorter carbon nanotube is, the greater frequency drift will be.Finally, based on continuum theory, the effect of monolayer bacteria on the intrinsic frequency of SWCNTs has been investigated. To describe the adsorption of carbon nanotubes with uniform distribution of bacterial layer, the Euler-Bernoulli beam of uniform load model has been used. In order to figure out how mass of bacterial layer affects the resonant frequency of the carbon nanotube resonators, the resonators both in bridged and in cantilevered configurations are studied. Then, comparing the resonant sensor of monolayer bacteria adsorbed model and single molecule adsorbed model to derive general analytical expressions, the similar regularity of frequency drift has been obtained. In addition, the numerical simulation and analysis of three-dimensional images results indicate that the bridged configurations model causes the greater frequency drift than the cantilever model, and uniform layer bacteria adsorbed model also causes the greater frequency drift than the single molecule adsorbed model by the system. The results illustrate that the new vibrational properties can be used for CNT-based mass sensors for further promote application.