Three-dimensional movies are everywhere these days, and the novelty is poised to become a big-screen mainstay. Now the field of microscopy is getting into the act, too, but the end product is very different from 3-D movies such as Toy Story 3 or Avatar.
Oh-Hoon Kwon and Ahmed Zewail of the California Institute of Technology report in the June 25 issue of Science a proof-of-principle for using a nanoscale imaging technique called electron tomography to produce movies of dynamic processes at miniature scales. (This is not new territory for Zewail, who won the 1999 Nobel Prize in Chemistry for his high-speed spectroscopy of the motion of atoms during chemical reactions.) The movies are composed of still frames that resolve the object in all three spatial dimensions, so although researchers cannot throw on a pair of 3-D glasses to see the object hovering before them (at least not yet), the microscopy technique reveals three-dimensional objects in all their structural complexity.
Each three-dimensional frame, or snapshot, comes from a series of two-dimensional samplings of the specimen under illumination by an electron beam. The specimen is imaged at a number of viewing angles by varying its tilt with respect to the beam, producing a collection of two-dimensional glimpses that together yields a 3-D map of the object.
In the new study, Kwon and Zewail rotated a specimen of carbon nanotubes 116 degrees through the electron beam, imaging the sample at each degree step. By repeating the process in quick succession, the researchers compiled a sequence of volumetric images that together form a movie, just as traditional motion pictures comprise a series of still images played back in quick succession.
Using the moviemaking technique, the researchers observed the nanotubes flexing and wiggling in response to laser heating. The video below, for instance, shows a bracelet-shaped nanotube structure over an 85-nanosecond span following a heating pulse. The imaging process, for which Caltech has filed a patent, could find use in studying fleeting temporal processes in biology and materials science, the researchers predict.
Image and video courtesy of Ahmed Zewail