Nanomanipulation experiments exploring frictional and mechanical properties of carbon nanotubes

In many cases in experimental science, the instrument interface becomes a l imiting factor in the efficacy of carrying out unusual experiments or preve nts the complete understanding of the acquired data. We have developed an a dvanced interface for scanning probe microscopy (SPM) that allows intuitive rendering of data sets and natural instrument control, all in real time. T he interface, called the nanoManipulator, combines a high-performance graph ics engine for real-time data rendering with a haptic interface that places the human operator directly into the feedback loop that controls surface m anipulations. Using a hand-held stylus, the operator moves the stylus later ally, directing the movement of the SPM tip across the sample. The haptic i nterface enables the user to "feel" the surface by forcing the stylus to mo ve up and down in response to the surface topography. In this way the user understands the immediate location of the tip on the sample and can quickly and precisely maneuver nanometer-scale objects. We have applied this inter face to studies of the mechanical properties of nanotubes and to substrate- nanotube interactions. The mechanical properties of carbon nanotubes have b een demonstrated to be extraordinary. They have an elastic modulus rivaling that of the stiffest material known, diamond, while maintaining a remarkab le resistance to fracture. We have used atomic-force microscopy (AFM) to ma nipulate the nanotubes through a series of configuration that reveal buckli ng behavior and high-strain resilience. Nanotubes also serve as test object s for nanometer-scale contact mechanics. We have found that nanotubes will roll under certain conditions. This has been determined through changes in the images and through the acquisition of lateral force during manipulation . The lateral force data show periodic stick-slip behavior with a periodici ty matching the perimeter of the nanotube.