World’s Smallest Propeller Could be Used for Microscopic Medicine

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.

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