Crawling bacteria provide the power to turn this micromotor. Scientists at the University of Tokyo and the National Institute for Advanced Industrial Science and Technology in Tsukuba, Japan built the device with processes similar to those used to fabricate integrated circuits. The "bacterial-propulsion units," a strain of Mycoplasma mobile, crawl clockwise in a groove underneath the motor's rotor, tugging the motor in a circle. It circles at twice the speed of a watch's second hand and doesn't generate much torque, but the researchers report that adding more bacteria would greatly improve the results. From Science News:
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.
