Science Alliance Annual Report
2008–2009
UT-ORNL Distinguished Scientists
UTK biochemistry and cellular and molecular biology and materials science and engineering; ORNL materials science and technology
David Joy
Nanomanufacturing with electron and ion beam imaging technology
It’s hard to imagine machinery a thousand times smaller than the width of a human hair. Still, scientists are optimistic that the technology for building useful nanodevices will lead to an array of new materials and products, all the way from longer-lasting batteries to “smart pills” that deliver the right drug dose at the right time. But, coming up with precise calibrations for nanotechnology’s equivalent of “tool-and-die” production will be tricky because the scales are smaller than most of today’s instruments can measure.
David Joy specializes in electron and ion beam imaging, electron optical analysis, and the precise measuring techniques needed to solve this difficult problem. His group searches for techniques that will provide absolute nanoscale calibrations.
Recently, Joy created a series of innovative tests to gauge the accuracy and performance of electron and ion-beam imaging tools. The tests were inspired by British physicist Lord Rayleigh’s nineteenth century insight that Moiré patterns, or fringes, could be used to test the perfection of diffraction gratings—a series of light-splitting, parallel lines or grooves on a transparent or reflective surface.
Often seen as rippling waves across a computer screen, Moiré fringes are interference patterns visible when two similar but slightly different grating patterns overlap.
Joy says the improved precision has already proven useful in an unexpected quarter. He and entomology graduate student Andrew Haddow are measuring the three-dimensional size and shape of mosquito eggs, less than one micrometer in width, to determine whether they come from one of the species that carry the West Nile virus. If identified as suspect, the eggs can be destroyed before they hatch and become a threat to public health.
Joy’s group is also part of a National Institutes of Health and Department of Energy sponsored project studying the effect that cerium oxide (CeO) nanoparticles have on living tissue, in this case E. coli.
Thought of as the material of choice for next generation catalytic converters, CeO particles can assume a long, sharp, needle-shaped form, potentially capable of penetrating cell walls. Scanning transmission and electron microscopies revealed that the CeO rarely penetrated E. coli cell walls. So, while they did stop growth, the microbes remained alive to resume growing once the CeO was removed. Interestingly, Joy’s group also found that their focused ion beam tool was an excellent scalpel, capable of cutting E. coli in half without any mechanical damage or distortion.