Researchers have discovered that common bacteria suspended in a solution can be made to turn microgears. This opens up the possibility of building hybrid biological machines at the microscopic scale. The researchers say the discovery demonstrates how microscopic swimming agents, such as bacteria or man-made nanorobots, in combination with hard materials, can constitute a “smart material“, which can dynamically alter its microstructures, repair damage, or power microdevices.
Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northwestern University produced microgears just 380 microns (0.38 mm) long with slanted spokes and placed them in a solution along with the common aerobic bacteria Bacillus subtilis. The researchers observed that the bacteria appeared to swim at random—but occasionally the organisms collided with the spokes of the gear and began turning it in a definite direction.
A few hundred bacteria work together in order to turn the gear. When multiple gears are placed in the solution with the spokes connected as in a clock, the bacteria will turn both gears in opposite directions, causing the gears to rotate in synchrony—even for long stretches of time.