Detecting mechanical resonance in carbon nanotubes via inter-tube electrical transport measurements

Detecting the mechanical resonance frequency of carbon nanotubes has strong potential applications that range from nano-scale balances to detect very small mass changes to ultra-sensitive bio-sensors. Detection of nanotube resonance requires elaborate and time-consuming techniques such as in-situ TEM, which limits the practical utility of this concept. In this paper we report a simple and accurate technique for detection of nanotube resonance by monitoring inter-tube electrical transport in a vibrating array of aligned multiwalled carbon nanotubes. The conductivity measurements are performed using a four-point probe in a direction perpendicular to the nanotube axis. We observe a dramatic decrease in the dc electrical resistance of the nanotube array at the mechanical resonance condition. We believe this is due to inter-tube impacts at resonance, which leads to an increase in the nanotube local temperature and hence increases the electron hopping rate. The impacting of the tubes could also enable localized tunneling of electrons through the nanotube array along with the hopping.