BACTERIA POWERED ROTOR

Uichi Hiratsuka and his colleagues “have chemically harnessed bacteria to a micromotor so that they can make the device's rotor slowly turn.”

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.

The scientists then coated the micrometer-long, pear-shaped bacteria with a solution containing biotin, a vitamin that readily binds to streptavidin.

The team released the treated bacteria into the grooves in a way that sent them mostly in one direction around the circle. As the microbes passed each of a rotor's supporting ridges, their biotin-treated cell membranes clung to the streptavidin coating, causing tugs on the tabs and thereby turning the rotor.

Slow and weak, the rotors circle at about twice the speed of the second hand on a watch and generate only a ten-thousandth as much torque as typical electrically powered micromachines do. By using more bacteria, the scientists could boost the torque 100-fold, Hiratsuka predicts.

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via pruned