AVS 51st International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoM

Paper NS-MoM11
Stiffness and Nonlinear Mechanical Properties of Single-Walled Carbon Nanotube Bundles

Monday, November 15, 2004, 11:40 am, Room 213D

Session: Carbon Nanotubes-Electrical Properties
Presenter: P. Jaroenapibal, University of Pennsylvania
Authors: P. Jaroenapibal, University of Pennsylvania
D.E. Luzzi, University of Pennsylvania
S. Evoy, University of Pennsylvania
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Nanoscale cantilevered resonators offer great potential as sensing devices due to their high sensitivity to added masses or external forces. Highly-sensitive resonators can be accomplished by using long, thin, stiff, low density, and high quality cantilevers. Hybrid carbon nanotubes represent a powerful platform for the development of tunable nanoresonator-based devices that would provide both high quality resonance and sensing specificity. We have studied the mechanical properties of single-walled carbon nanotube (SWNT) bundles through in-situ transmission electron microscope (TEM) observation of mechanical resonance. The observed resonant frequencies of SWNT bundles ranged from 0.2 - 9 MHz, with resonance qualities Q ranging from 77 to 800. An effective Young's modulus of E* = 76 ± 4 GPa is extracted from the resonance data. This relatively low value indicates that the individual SWNTs are weakly interacting within the bundle, where slippage can occur due to the low sliding resistance between the atomically smooth surfaces of neighboring tubes. Departure from Lorentzian responses, an onset of non-linear behavior was observed under large actuation amplitudes. Specifically, bi-stable responses were observed in 4 µm long and 30 nm wide bundles when their end-point displacement approached a critical amplitude of x@sub c@ = 800 nm. Such non-linear behavior reveals the onset of inter-tube interactions within the bundle when sufficiently large bending is applied. We will discuss this non-linear data with respect to an effective Poisson ratio that results from inter-tube interactions, and describe the impact of beam irradiation on such interactions. Mechanical properties of hybrid carbon nanotubes in which fullerenes or other molecules are encapsulated will also be discussed.