Adhesive and Mechanical Properties of Carbon Nanotube Probes Contacting Chemically-Treated Surfaces

Abstract

Carbon nanotubes are useful in a variety of measurement applications. In the case of Atomic Force Microscopes (AFMs), carbon nanotubes can be affixed to the tip of the AFM cantilever to improve image resolution and enable images of surfaces with deep crevices and trench structures. In this paper, the mechanical response of long, straight, small walled carbon nanotubes (SWNTs) under compressive and tensile load is examined with an atomic force microscope. Multi-dimensional force spectroscopy (MDFS) is used to simultaneously measure the cantilever resonant frequency, deflection, and scanner motion. The acquired force curves reveal that the SWNT buckles shortly after contact is initiated. As the scanner continues to rise and then reverses direction, the SWNT undergoes a number of adhesion/sticking episodes, buckling, and slip events. The bulk properties of the nanotube are estimated by measuring the shift in natural frequency during tension. Finally, the carbon nanotube is modeled as an elastica in order to predict the post-buckled shape of the SWNT. By comparing the model results with MDFS results, the static coefficient of friction between the SWNT and a variety of surfaces is estimated. The study suggests that MDFS has a wide applicability for studying the mechanical and adhesive properties of various nanotubes, nanorods and nanofibers.

Peeling of Long, Straight Carbon Nanotubes from Surfaces

“…Buchoux et al [17,18] have previously examined axial compression of SWNT on graphite and mica substrates. We present herein new evidence that adhesion between the surface and the nanotube-modified AFM tip can significantly alter the mechanical behavior of the nanotube [36]. Finally, we identify characteristic signatures in the deflection and frequency response of the cantilever that indicate buckling and slip-stick events of the CNT under compression and its adhesion to the surface under tension.…”

“…Interestingly, after the buckling event (the system is now described as postbuckled), the force required to overcome the adhesion at the pinned end of the nanotube and enter the slip-stick domain is, by definition, the frictional force. A prediction can be made about the shape of the buckled nanotube as it undergoes further compression by applying an elastica model of a postbuckled column [36,39].…”

“…It is assumed that the contact point is directly beneath the AFM tip; however, the probe tip can be moved to the left or right by varying . The differential equations and associated boundary conditions were solved using the Matlab solver for boundary-value problems, bvp4c, as previously described [36,39]. Through the solution of the boundaryvalue problem, the horizontal and vertical forces at the pinned endpoint can be calculated at different compression steps.…”

Empirical Correlation of the Morphology of Coiled Carbon Nanotubes with Their Response to Axial Compression

“…The objectives of the work presented herein were to determine the stiffness of CCNTs to axial compression and to correlate this stiffness with their composition/structure. Our approach involves attaching an individual nanotube to the tip of an atomic force microscope (AFM) probe and then using this instrument to apply a controlled mechanical load to the nanocoil [22][23][24]. Mechanical loading of straight or coiled nanotubes results in compression, buckling, and sliding on the substrate surface [9,22,23,[25][26][27][28][29][30][31][32].…”