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Posted: November 4, 2008
(Nanowerk News) University of Michigan professor John Hart has made faces of Barack Obama using nanotechnology, specifically carbon nanotubes, and imaged them using a scanning electron microscope. Each face consists of millions of vertically-aligned carbon nanotubes, grown by a high temperature chemical reaction.
The nanobama structures are made of carbon nanotubes, and the pictures were taken using optical and electron microscopes. Carbon nanotubes (CNTs) are tiny hollow cylinders of carbon; the diameter of a CNT is tens of thousands of times smaller than a human hair, and CNTs are several times stronger and stiffer than steel. CNTs are grown by a high-temperature chemical reaction, using patterns of nanoscale metal catalyst particles arranged in the shapes of the faces, text, and flags that you see in the images. Each face contains millions of parallel nanotubes, standing vertically on the substrate like a forest of trees. If you were standing next to the nanotubes as they grow, and each nanotube was a 1 foot (0.3 meter) diameter tree, the trees would be growing at over 500 miles per hour! The nanobama faces are approximately 0.5 millimeter wide, or about ten times the width of a human hair.
On his Nanobama site Hart describes how the nanobamas are made:
(1) convert a cartoon of Barack Obama to a line drawing
(2) shrink the drawing and print it onto a glass plate (mask), using a laser system
(3) shine ultraviolet light through the mask, and onto a thin layer of polymer on a silicon wafer, thereby patterning the polymer by photolithography
(4) coat the wafer with a thin layer of catalyst nanoparticle "seeds" for nanotube growth
(5) remove the remaining polymer, leaving the catalyst seeds in the shapes of the nanobamas
(6) grow the CNTs from the catalyst patterns, by placing the wafer in a high-temperature furnace and filling the furnace with a carbon-containing gas
(7) take pictures of the structures, which are barely visible to the naked eye, using electron and optical microscopes