An article in Science News by Marissa Cevallos explains how research reported last week in Science (abstract) could lead to upgraded electron microscopes that would use corkscrew electron beams to capture images of tiny subjects, and could possibly also lead to the ability to grab and manipulate individual atoms. From “A twisted way to take pictures“:
Powerful lab microscopes may soon get a screwy upgrade.
By twisting a stream of electrons into a tornado-like vortex, physicists have created a new type of beam to take snapshots of atoms, biological tissue and tiny computer parts, a team reports in the Jan. 14 Science.
Though they haven’t put one in a microscope yet, such a vortex beam could be used in the near future to take sharper pictures, says Ben McMorran, a physicist who led the research at the National Institute of Standards and Technology in Gaithersburg, Md. What’s more, the beams could possibly grab onto atoms to manipulate them, other researchers say.
Electrons, which can behave like waves as well as particles, have a wavelength much smaller than that of visible light. So compared with light, or optical, microscopes, the electron microscope excels at probing tiny things like atoms.
Electron microscopes snap images of minuscule objects by shooting a beam of electrons at a target and recording where the electrons scatter. A microscope using a vortex electron beam would work similarly, except the electron beam must first pass through a hologram that twists the beam into a helix, says McMorran. A beam that spirals offers even better resolution than a straight beam because its energy isn’t concentrated in the beam’s center, which is difficult to focus.
Holograms, like the colorful ones on credit cards, are formed when light bounces off or through an etched surface. In this case, the “hologram” is a thin layer of silicon nitride that McMorran’s team etched with lines a few nanometers apart. …
Transforming an electron microscope into a vortex microscope is as simple as slipping a thin hologram into a preexisting slot, according to mechanical engineer Rodney Herring of the University of Victoria in Canada.
One intriguing application would be to use the beams to grab onto individual atoms, Herring says. Electrons in a twisted beam couple with electrons in the atoms of a material, and scientists controlling the electron microscope could use its lenses like a joystick to move the beam (and a captive atom) around.
“Now we have hands that can manipulate atoms and electrons,” says Herring.
The production and application of electron vortex beams had been described in a paper published a few months earlier in Nature (abstract), but the more recent work “could potentially yield 25 times better resolution.” McMorran is quoted as saying “Whether this will lead to a useful application to manipulate particles or atoms remains to be demonstrated”.
Note that this research was made possible by the ability to nanofabricate holograms by etching lines a few nanometers apart. We have another example here of current nanotechnology leading toward advanced nanotechnology, and eventually molecularly manufacturing, by providing tools to build better tools.
