NANOTECH BREAKTHROUGH - Putting Bends in Carbon Nanotubes
For the first time, a group led by MAE professor Sungho Jin has made carbon nanotubes bent into several shapes. Variations of the technical achievement, reported in a series of recent papers in Nano Letters and other journals, could lead to the use of these electrically conducting fibers as vastly smaller electrical connectors in integrated circuits and nanoscale springs, solenoids, and other components.
"Controlling nanotube geometry is necessary to realize the many promised applications of these materials," says Jin. His group is exploiting nanotubes' response to electric field lines in a chamber, with those lines radiating at various angles. For example, the group positioned growing nanotubes in left- and right-oriented field lines to make a variety of shapes including Ls and zig-zags.
Currently, interconnections between microcircuit devices are made with metal alloy solders. However, microcircuit devices contain materials that expand and contract at different rates than the solders during cycles of heating and cooling, which eventually cause cracking at the interconnections.
"If these interconnections were made with electrically conducting nanotube springs instead of solder, not only would we need much less space to make these interconnections, but the thermal-expansion mismatch wouldn't matter because the interconnections are flexible," says Jin."We call it the compliant nano-interconnect."
Graduate students in Jin's group initiate the growth of individual nanotubes with a catalyst. Making the catalyst smaller and smaller during nanotube growth can create a sharply pointed needle."Researchers may use such nano-needles to inject genes into cells for gene therapy," says Jin. Nano-needles and nanotubes in aligned configuration can also be applied in a technology called projection electron-beam lithography, which is used to pattern semiconductor circuits. An array of such nano-needles, says Jin, could be used to carry out aerial patterning instead of the current slow and costly single beam-based electron lithography.