Controlled manipulation of molecular samples with the nanoManipulator

Making further advances in such diverse problems as building more powerful computers, measuring material properties of biological samples, or exploring fundamental physical laws on the atomic level requires gaining access to the nanoworld. The nanoManipulator system adds a virtual-reality interface to an atomic-force microscope (AFM), thus providing a tool that can be used by scientists to image and manipulate nanometer-sized molecular structures in a controlled manner. As the AFM tip scans the sample, the tip-sample interaction forces are monitored, which. in turn, can yield information about the frictional, mechanical, material, and topological properties of the sample. Computer graphics are used to reconstruct the surface for the user, with color or contours overlaid to indicate additional data sets. Moreover, a force feedback stylus, which is connected to the tip via software, allows the user to directly interact with the macromolecules. This system is being used to investigate carbon nanotubes (CNT's), deoxyribonucleic acid (DNA), fibrin, adeno-and tobacco mosaic virus. Nanotubes have been bent, translated, and rotated to understand their mechanical properties and to investigate friction on the molecular level. Using AFM lithography in combination with the nanoManipulator, the electromechanical properties of CNT's ale being investigated. The rupture forces of DNA and fibrin fibers have been measured and the elastic moduli of viruses are being studied. It is now also possible to insert this system into a scanning electron microscope which pro,ides the user with continuous images of the sample, even while the AFM tip is being used for manipulations. Investigators are invited to apply to use the system as described on the web at http://www.cs.unc.edu/Research/nano/doc/biovisit.html.