The now-classic science fiction
movie Fantastic Voyage is becoming more like science and less like
fiction thanks to the work of Rice University chemist James Tour.
Scientists led by Tour at the university are making progress
toward a nanoscale submersible vehicle that potentially could be used
for drug delivery and other medical purposes. Tour is known for his
expertise with molecular machines, having created a the world’s first nanocar a decade ago.
Designed
by Tour and his team of student researchers, the single-molecule sub is
built using 244 atoms. It is capable of swimming through a fluid with a
tail-like propeller that spins at more than 1 million RPM. Each full
revolution of the propeller moves the submersible forward by 18
nanometers, which equates to a speed of one inch per second. Though slow
compared to other larger vehicles, that speed is breakneck for
molecular-level machines.
The
motor in the nanoscale submersible is powered by ultraviolet light,
which causes the double bond holding the rotor to the body of the sub to
break into a single bond. This breakage cases the rotor to turn a
quarter turn. The motor, by returning to its normal lower energy state,
turns the rotor another quarter turn. This turning process continues as
long as the sub is exposed to UV light. Though the sub moves easily
through liquids, its does so randomly as the rotor mechanism is not
designed for steering.
To
help measure the movement of the submersible, the researchers partnered
with professor Gufeng Wang at North Carolina State University. The team
of researchers used a custom confocal fluorescence microscope to track
the sub as it traveled through a solution. The researchers flooded the
sub with UV light to provide enough power for movement, and a laser to
light up the sub’s pontoons, which fluoresce red when excited by a
laser. Using this setup, the Rice team was able to analyze the movement
of one single-molecule sub at a time. The Rice researchers published
their work in the journal Nano Letters.
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