Cutting Edge 'Nanoknife' Made

Researchers have designed a carbon nanotube knife that, in theory, would work like a cheese slicer, precisely cutting thin slices of cells. The scientists said the "nanoknife" could one day become a tabletop biology tool.

The research team from the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU) presented their results earlier this month in the paper "Fabrication and Mechanical Characterization of Carbon Nanotube Based Nanoknives" at the 2006 International Mechanical Engineering Congress and Exposition in Chicago.

Scanning electron micrograph of a prototype "nanoknife" shows a single carbon nanotube stretched between two tungsten needles (Color added for clarity). The triangular probe is the tip of an atomic force cantilever used to determine the breaking point of the knife. (Image: NIST/CU)

For years, biologists have wrestled with conventional diamond or glass knives, which cut frozen cell samples at a large angle, forcing the samples to bend and sometimes later crack. Because carbon nanotubes are extremely strong and slender in diameter, they make ideal materials for thinly cutting precise slivers of cells. In particular, scientists might use the nanoknife to make three dimensional images of cells and tissues for electron tomography, which requires samples less than 300 nm thick, the researchers said.

By manipulating carbon nanotubes inside scanning electron microscopes, scientists 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. In the resulting prototype, the nanotube stretches between two ends of a tungsten wire loop. The knife resembles a steel wire that cuts a block of cheese.

To begin demonstrating the feasibility of their knife design, the researchers assessed its mechanical strength in force tests, applying increasing pressure to the device. The team found that the welds were the weakest point of the nanoknife, and they are now experimenting with alternative welding techniques. The researchers plan to test the nanoknife on a block of wax later this year (cells typically are immobilized in wax for dissection and microscopy.)

For more information, visit: www.nist.gov