Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northwestern University, Evanston, have discovered that common bacteria can turn microgears when suspended in a solution, providing insights for design of bio-inspired dynamically adaptive materials for energy.
“The gears are a million times more massive than the bacteria,” said physicist and principal investigator Igor Aronson. “The ability to harness and control the power of bacterial motions is an important requirement for further development of hybrid biomechanical systems driven by microorganisms.”
The microgears with slanted spokes, produced in collaboration with Northwestern University, are placed in the solution along with common aerobic bacteria, Bacillus subtilis. Andrey Sokolov of Princeton University and Igor Aronson from Argonne, along with Bartosz A. Grzybowski and Mario M. Apodaca from Northwestern University, discovered that the bacteria appear to swim around the solution randomly, but occasionally the organisms will collide with the spokes of the gear and begin turning it in a definite direction.
A few hundred bacteria are working together in order to turn the gear. When multiple gears are placed in the solution with the spokes connected like in a clock, the bacteria will begin turning both gears in opposite directions and it will cause the gears to rotate in synchrony for a long time.
“There exists a wide gap between man-made hard materials and living tissues; biological materials, unlike steel or plastics, are “alive.” Biomaterials, such as live skin or tissue, consume energy of the nutrients to self-repair and adapt to their environment,” Aronson said. “Our 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.”
The speed at which the gears turn can also be controlled through the manipulation of oxygen in the suspended liquid. The bacteria need oxygen in order to swim and by decreasing the amount of oxygen available, they will begin to slow down. If you eliminate the oxygen completely, the bacteria go into a type of “sleep” and stop completely.
Once the oxygen is reintroduced into the system, the bacteria “wake up” and begin swimming once again.
For millennia, people have hitched beasts to plows to exploit the animals’ strength and energy. In a modern variant of that practice, scientists have chemically harnessed bacteria to a micromotor so that they can make the device’s rotor slowly turn.
The new work might lead to improved lab-on-a-chip devices and engines to propel microrobots, says Yuichi Hiratsuka, now of the University of Tokyo “Todai” redirects here. For the restaurant called Todai, see Todai (restaurant). The University of Tokyo who codeveloped the bacteria-powered micromotor. He and his colleagues describe the research in an upcoming Proceedings of the National Academy of Sciences The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences. . The novel micromachine “is an important step in integrating biological components into microengineered systems,” comments bioengineer William O. Hancock of Pennsylvania State University Pennsylvania State University, main campus at University Park, State College; land-grant and state supported; coeducational; chartered 1855, opened 1859 as Farmers’ High School. in University Park.
// 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 silicon dioxide: see silica. (SiO2) A hard, glassy mineral found in such materials as rock, quartz, sand and opal. In MOS chip fabrication, it is used to create the insulation layer between the metal gates of the top layer and the silicon elements below. 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. ( Mycoplasma: … bacteria that make up the genus Mycoplasma … are among the smallest of bacterial organisms. The cell varies from a spherical or pear shape to that of a slender branched filament)
The scientists then coated the micro-meter-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.
– via science news Sept 2006