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| Schematic of micro- and nanopropellers in hyaluronan gels. The polymeric mesh structure hinders the larger helices from translating effectively, whereas smaller propellers with a diameter close to the mesh size can pass through the network without being affected by the macroscopic viscoelasticity caused by the entangled polymer chains. |
If you thought that the most impressive news in shrinking technology
these days was smart watches, think again. Scientists are quietly
toiling in their laboratories to create robots that are only nanometers –
billionths of a meter – in length, small enough to maneuver inside the
human body and possibly inside human cells. The impact of these
miraculous microscopic machines on medicine can only be imagined, but
there is no doubt that it will be significant.
One
of the first steps in creating these robots is figuring out how to make
them move. In a paper published in the June 2014 issue of ACS Nano,
an Israeli and German team announced that they had succeeded in
creating a tiny screw-shaped propeller that can move in a gel-like
fluid, mimicking the environment inside a living organism. The team is
comprised of researchers from theTechnion-Israel Institute of
Technology’s Russell Berrie Nanotechnology Institute, the Max Planck
Institute for Intelligent Systems, and the Institute for Physical
Chemistry at the University of Stuttgart, Germany.
The filament that makes up the propeller, made of silica and nickel,
is only 70 nanometers in diameter; the entire propeller is 400
nanometers long. (A nanometer is one billionth of a meter.) “If you
compare the diameter of the [nanopropellers] with a human blood cell,
then the [propellers] are 100 times smaller,” said Peer Fischer, a
member of the research team and head of the Micro, Nano, and Molecular
Systems Lab at the Max Planck Institute for Intelligent Systems. They
are so small, in fact, that their motion can be affected by the motion
of nearby molecules (known as Brownian motion).
The team already knew that tiny propellers moved well through water,
but to test if they could move through living organisms, they chose
hyaluronan, a material that occurs throughout the human body, including
the synovial fluids in joints and the vitreous humor in your eyeball.
The hyaluronan gel contains a mesh of long proteins called polymers; the
polymers are large enough to prevent micrometer-sized propellers from
moving much at all. But the openings are large enough for
nanometer-sized objects to pass through. The scientists were able to
control the motion of the propellers using a relatively weak rotating
magnetic field.
The findings were somewhat surprising. The team expected that they
would have trouble controlling the motion of the nanopropellers, since
at their size they start to be governed by diffusion, just as if they
were molecules. But because the nanopropellers are the same size as the
mesh in the gel, they “actually display significantly enhanced
propulsion velocities, exceeding the highest speeds measured in glycerin
as compared with micro-propellers, which show very low or negligible
propulsion,” said study co-author Associate Professor Alex Leshanksy of
the Technion Faculty of Chemical Engineering.
While the nanopropellers are astonishing for their technical
complexity, the real significance is how they might affect medicine.
“One can now think about targeted applications, for instance in the eye
where they may be moved to a precise location at the retina,” says
Fischer. Scientists could also attach “active molecules” to the tips of
the propellers, or use the propellers to deliver tiny doses of
radiation. The applications seem wide, varied, and exciting.
The Technion-Israel Institute of Technology is a major source of
the innovation and brainpower that drives the Israeli economy, and a key
to Israel’s renown as the world’s “Start-Up Nation.” Its three Nobel
Prize winners exemplify academic excellence. Technion people, ideas and
inventions make immeasurable contributions to the world including
life-saving medicine, sustainable energy, computer science, water
conservation and nanotechnology. The Joan and Irwin Jacobs
Technion-Cornell Innovation Institute is a vital component of Cornell
NYC Tech, and a model for graduate applied science education that is
expected to transform New York City’s economy.
written by : Kevin Hattori ,American Technion Society.
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