November 24th, 2006
Nanoknives to cut cells
American researchers have built a carbon nanotube knife. According to the National Institute of Standards and Technology (NIST), this nanoknife will be used to cut and study cells. With this new tool, scientists and biologists will be able to make 3D images of cells and tissues for electron tomography, which requires samples less than 300 nanometers thick. And as cells are usually stored in wax for dissection, the researchers plan to test their nanoknives on a block of wax later this year. But read more…
This research work, which has been conducted at NIST and the University of Colorado at Boulder (CU), has recently been presented at the 2006 ASME International Mechanical Engineering Congress & Exposition. It is available in the Proceedings of this conference for $850 on a DVD (or $680 if you're a member), along with more than 1,500 other scientific papers.
But if you think this price is a little bit steep, you can search for the paper named "Fabrication and mechanical characterization of carbon nanotube based nanoknives" on the conference website (code: IMECE2006-14659). Here is the abstract.
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.
Below is a scanning electron micrograph of a prototype 'nanoknife' showing a single carbon nanotube stretched between two tungsten needles. The triangular probe is the tip of an atomic force cantilever used to determine the breaking point of the knife (Color added for clarity.) (Credit: NIST/CU). You can find this image at various resolutions here as part of the NIST Image Gallery.
Now, let's return to NIST Tech Beat to read a bunch of 'nano-invented' words.
By manipulating carbon nanotubes inside scanning electron microscopes, 21st-century nanosmiths have begun crafting a suite of research tools, including nanotweezers, nanobearings and nano-oscillators. To design the nanoknife, the NIST and CU scientists welded a carbon nanotube between two electrochemically sharpened tungsten needles.
It doesn't seem that this tool will be available before a while. The researchers have "found that the welds were the weakest point of the nanoknife, and they are now experimenting with alternative welding techniques."
It also seems that the team has lost one of its leaders: Roop L. Mahajan became director of the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech on July 1, 2006, even if it's not mentioned by NIST.
Sources: NIST Tech Beat, November 22, 2006; and various websites
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