The Tiniest Propeller Ever Can Sneak Between Cells

Researchers want to use microscopic nanobots for drug delivery and other tasks inside the human body, but there are still places the micro machines can't get. Now, scientists have made the smallest bot yet, a magnet-guided corkscrew so tiny, it can sneak through the pores in human connective tissue.

A research team led by Dr. Peer Fischer at the Max Planck Institute for Intelligent Systems in Germany has made a tiny helical nanopropeller from a filament of silica and nickel just 70 nanometers in diameter. That's more than 1,000 times smaller than the width of a human hair, or 100 times smaller than a single red blood cell, making the wee machine the tiniest nanopropeller humanity has ever created.

Using a weak, rotating magnetic field, the researchers are able to get the corkscrew nanopropeller spinning in fluid, propelling it forward. The nanobot is so small, it gets tripped up by molecules of pure water—Brownian motion, the random low-energy wiggling of H2O molecules, are enough to deflect the little submarines.

But the bots zip faster than any previously-created nanodevice in viscoelastic hyaluronan gels, the type of robust connective tissue found in skeletal joints and eyeballs. That's because the little corkscrews are so small, they cruise right through the gaps in the connective tissue mesh.

That record-breaking tininess is huge for drug delivery—theoretically, these precision-guided corkscrews could go places larger micropropellers can't. "One can now think about targeted applications, for instance in the eye where they may be moved to a precise location at the retina," Dr. Fischer told the American Technion Society. Researchers imagine putting active nose-cones on the mini machines, using them to deliver micro-doses of drugs or radiation right to individual cells.

The field of precision-guided nanobot medicine still has a long way to go before that kind of therapy is feasible. But with this new type of astoundingly tiny machine, and its ability to traverse formerly impassible body parts, the dream of guided drug delivery just got a little more feasible. [ACS Nano; American Technion Society via Gizmag]