Scientists at the University of Sheffield and the University of Barcelona have devised a microscopic swimming robot that could deliver drugs inside the body by mimicking the wheel of a paddle-steamer.
Scientists created their machine from magnetic beads, which bind to DNA.
By applying a magnetic field the beads start spinning and researchers discovered they move through water at about 1 micrometre per second.
"I didn't expect to see real propulsion like that seen in bacteria to tell the truth," the Telegraph quoted Dr Pietro Tierno, of Barcelona University, as saying.
The research team says that its technology can easily be shrunk to nanoscale - at which size it would be useful as a drug carrier.
Co-researcher Dr Ramin Golestanian, of Sheffield University, said: "It's like a unicycle wheel with the smaller bead as the pedal making it go around with the DNA as the pedal shaft. Microscale and nanoscale hydrodynamics are not all that different."
The properties the device needs to swim should be present in small blood vessels.
For microscale swimmers the resistance of water presents a much bigger barrier to motion than we are used to on everyday scales. It is like swimming through honey for a human.
"In a stiff fluid what you achieve in half of your swimming cycle you undo in the next half-cycle. That's why bacteria like E coli use a rotating corkscrew-like tail to propel themselves forward," Golestanian said.