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Published November 2008 | Supplemental Material
Journal Article Open

Nanoscale Mechanical Drumming Visualized by 4D Electron Microscopy


With four-dimensional (4D) electron microscopy, we report in situ imaging of the mechanical drumming of a nanoscale material. The single crystal graphite film is found to exhibit global resonance motion that is fully reversible and follows the same evolution after each initiating stress pulse. At early times, the motion appears "chaotic" showing the different mechanical modes present over the micron scale. At longer time, the motion of the thin film collapses into a well-defined fundamental frequency of 1.08 MHz, a behavior reminiscent of mode locking; the mechanical motion damps out after ∼200 μs and the oscillation has a "cavity" quality factor of 150. The resonance time is determined by the stiffness of the material, and for the 75 nm thick and 40 μm square specimen used here we determined Young's modulus to be 1.0 TPa for the in-plane stress−strain profile. Because of its real-time dimension, this 4D microscopy should have applications in the study of these and other types of materials structures.

Additional Information

© 2008 American Chemical Society. Received October 1, 2008. Publication Date (Web): November 12, 2008. We thank Drs. Fabrizio Carbone, Sang Tae Park, and Petros Samartzis for their help in the preparation of specimens and the automation. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research in the Gordon and Betty Moore Center for Physical Biology at Caltech. Research on biological imaging was supported by the National Institutes of Health. Supporting Information: A movie showing the time-resolved drumming of graphite. The frames of this movie include those depicted in Figure 2A and are the basis for the image cross correlation plots in Figure 3. The movie has been slowed down by ∼106 times with respect to real time so that the fast drumming motion can be observed. This material is available free of charge via the Internet at http://pubs.acs.org.

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