To make the motors, Hiratsuka’s team, led by Taro Q.P. Uyeda of the National Institute for Advanced Industrial Science and Technology in Tsukuba, Japan, borrowed fabrication techniques from the microelectronics industry.

The machinery of each motor consists of two parts: a ring-shaped groove etched into a silicon surface, and a star-shaped, six-armed rotor fabricated from silicon dioxide that’s placed on top of the circular groove. Tabs beneath the rotor arms fit loosely into the groove.

To prepare the bacterial-propulsion units, the team used a strain of the fast-crawling bacterium Mycoplasma mobile that was genetically engineered to crawl only on a carpet of certain proteins, including one called fetuin. The researchers laid down fetuin within the circular groove and coated the rotor with a protein called streptavidin.