Monthly Archives: November 2006

Nano-knives and superplastic nanotubes

First, the nano-knife (via slashdot):

A prototype microtome knife for cutting ~100 nm thick slices of frozen-hydrated biological samples has been constructed using multiwalled carbon nanotubes (MWCNT). A piezoelectric-based 3-D manipulator was used inside a Scanning Electron Microscope (SEM) to select and position individual MWCNTs, which were subsequently welded in place using electron beam-induced deposition (EBID).

The device employs a pair of tungsten needles with provision to adjust the distance between the needle tips, accommodating various lengths of MWCNTs. We have performed experiments to test the breaking strength of the MWCNT in the completed device using an atomic force microscope (AFM) tip. An increasing force was applied at the midpoint of the nanotube till the point of failure, which was observed in-situ in the SEM.

Next, the superplastic nanotubes of carbon:

The theoretical maximum tensile strain — that is, elongation — of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.