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The researchers then coat the nanotube with a thin
film of gold about 10-50 nanometers thick (a nanometer is 1 billionth
of a meter.) The gold layer is then coated with an insulating polymer
coating about 10 nanometers thick. Lastly, the researchers use a
focused ion beam to slice off the end of the nanotube, exposing a
conducting ring of gold sandwiched between an insulating core and an
insulating outer ring.
The process yields nanoelectrodes with a diameter
of 100 nanometers, and a length of up to 30 microns.
Because the nanotube is attached to a much larger
probe, the researchers can manipulate the nanotube like a needle. They
can control precisely where the nanotube penetrates a cell, for
example, and even pinpoint smaller cell structures, such as the
nucleus or mitochondrion.
"Nanoelectrodes offer new opportunities for
electrochemical sensing in intracellular environments," said Yu, who
will describe the fabrication process and demonstrate the feasibility
of nanoelectrodes at the March meeting of the American Physical
Society, to be held in Denver, March 5-9. "By functionalizing the
active area of the nanoelectrode with an appropriate chemical, we can
target the detection of specific chemical species."
The researchers have demonstrated that their
nanoelectrode can sense the chemical environment within a droplet 10
microns in diameter. Their next step is to show that the probe can
penetrate the cellular membrane of a living cell, without damaging the
cell. |
