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Research Topics:   Nanoscale Sciences         NEMS         TAMS         Nanocontacts         Magnetic Studies         Engineered Biomotors   Tools Research         AIMS         SEM/AFM         Nanomanipulator         3D Force Microscope         Mixing Model/Experiment   Biomedical Research         Cystic Fibrosis         Fibrin And Blood Clotting         Gene Therapy and Viruses         DNA         Cell Division         Bacterial Motility         Molecular Motors  Project Groups:   CISMM         (Computer Integrated         Systems for Microscopy         and Manipulation) ;  Nanoscale Education ;  NCCNM         (North Carolina         Center for Nanoscale         Materials)
		Atomic Gear Teeth and a Nano-Rheostat NANO-CONTACTS and COMMENSURATE CONTACT Multiwall Carbon Nanotubes (MWCNT) on Graphite (HOPG) NANO-CONTACTS: The details of the atomic structure of surfaces can profoundly affect the mechanical properties (friction and modes of motion) and the electronic properties (electrical resistance) of a nano-contact. Our studies focus on the CNT on HOPG system where both contacting surfaces are graphene sheets. Through nanomanipulation, we study the effect of the commensurability (registry of the contacting lattices) on the tribological and electronic properties of the contact. Evidence of Commensurate Contact: As the carbon nanotube is rotated in the plane of the graphite substrate, it comes into commensurate contact every 60 degrees. Commensurate contact is apparent through a ~10 fold increase in the lateral force required to move the CNT. Gear-like Rolling Motion: When the CNT is pushed while in commensurate contact, it undergoes gear-like rolling motion with the atoms of the contacting surfaces acting as the gear teeth. The evidence of this motion is three-fold: 1. translation without in-plane rotation, 2. changes in the imaged shape of the CNT consistent with rolling motion, and 3. periodicity in the force required to push the tube equal to its circumference. Nano-Rheostat: The electrical contact resistance between the CNT and graphite substrate varies with the degree of commensurability. We use the nanoManipulator to rotate the nanotube in-plane and measure the contact resistance as a function of relative lattice orientation.