Carbon Nanotubes Mimics Nature’s Design in Bionics

Mimicking the human nervous system for bionic applications could become
a reality with the help of a method developed at Oak Ridge National Laboratory
(ORNL) to process carbon nanotubes.

While these nanostructures have electrical and other properties that
make them attractive to use as artificial neural bundles in prosthetic devices,
the challenge has been to make bundles with enough fibers to match that of a
real neuron bundle. With current technology, the weight alone of wires required
to match the density of receptors at even the fingertips would make it
impossible to accommodate. Now, by adapting conventional glass fiber drawing
technology to process carbon nanotubes into multichannel assemblies,
researchers believe they are on a path that could lead to a breakthrough.

“Our goal is to use our discovery to mimic nature’s design
using artificial sensors to effectively restore a person’s ability to
sense objects and temperatures,” Ilia Ivanov, a researcher in the Center
for Nanophase Materials Sciences Division, said in a news release. Ivanov and
colleagues at ORNL recently published a paper in Nanotechnology that outlines
the method of processing loose carbon nanotubes into a bundle with nearly
20,000 individual channels.

Ultimately, the goal is to duplicate the function of a living system by
combining the existing technology of glass fiber drawing with the
multi-functionality of sub-micron (0.4 micron) scale carbon nanotubes,
according to Ivanov, who described the process.

“We make this material in a way similar to what you may have done
in high school when making a glass capillary over a Bunsen burner,” Ivanov
said. “There, you would take the glass tube, heat it up and pull, or draw,
as soon as the glass became soft.”

Ivanov and John Simpson of the Measurement Science and Systems
Engineering Division are doing something similar except they use thousands of
glass tubes filled with carbon nanotube powder. After several draw cycles, they
demonstrated that they could make fibers just four times thicker than a human
hair containing 19,600 sub-micron channels with each channel filled with
conducting carbon. Each carbon nanotube-containing channel is electrically
insulated from its neighbors by glass so it can be used as an individual
communication channel.

“The human hand has a density of receptors at the fingertips of
about 2,500 per square centimeter and about 17,000 tactile receptors in the
hand,” Ivanov said. “So in terms of density of channels, we are
already in the range needed for 17,000 receptors in the hand.”

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