At Japan’s National Institute of Advanced Industrial Science and Technology near Tokyo, Hiratsuka and his colleagues experimented with one of the most rapid crawling bacteria, Mycoplasma mobile. This pear-shaped microbe, a millionth of a meter long, can glide over surfaces at up to seven-tenths of an inch an hour. Translated to a 6-foot-tall (180-centimeter-tall) runner, this roughly equates to 20 mph (32 kilometers per hour). The researchers built circular pathways coated with sugary proteins, which the microbe needs to stick to in order to glide over surfaces. They then docked a rotor onto the track and coated the bacteria with vitamin B7, which acted like glue to yoke the germs to the cog. They also genetically modified the microbes so they stuck to their tracks more stably.
The scientists created roughly 20,000 rotors on a silicon chip. Each cog is etched from silica, which sand is made of, and is 20 microns wide, or roughly a fifth the diameter of a human hair. In addition to helping drive micro-robots, Hiratsuka suggested that bacteria-powered motors could help propel micropumps in lab-on-a-chip devices. “Alternatively, we may be able to construct electronic generator systems, which generate electric energy from an abundant chemical source — glucose in the body,” he said.