Engine made from bacteria

A challenge in developing micro robots is to shrink the motor and the power supply. US scientists have found a solution to this problem: Take advantage of the microbial motion of self to push small molecules-sized objects in liquids.

Many types of bacteria move in liquids by twisting twisted-shaped tails - called flagella - at relatively high speeds. These tails are about 20 nanometers in diameter and approximately 10,000 nanometers long.

Bacterial tails.
(Photo: scari.org)

Two researchers, Metin Sitti and Bahareh Behkam, at the University of Pennsylvania (USA), used bacteria to motivate and control their movements with chemicals. They started by attaching many S. marcescens bacteria to polystyrene chains about 10 microns in diameter. Tiny robots are introduced into a soluble mixture of water and glucose.

The bacteria itself is only about one-fifth the size of a polystyrene chain. They are attached to each other by electrostatic forces, Van der Waals forces and reactions between hydrophobic fatty acids. When bacteria rotate their tails, they push the chains forward with a speed of about 15 microns per second.

In order for the bacteria to stop moving, the two researchers added copper sulphate to the compound. Copper ions cling to the tail of bacteria and prevent their movement. In order for the bacteria to become active again, they added ethylene diamine tetra acetic acid (EDTA) to the solution. EDTA will ' confine ' copper ions on the bacterial tail, allowing them to move back. The spin of the tail can be turned on and off in this way for an unlimited number of times.

Using bacteria as an engine has many advantages, the two experts affirmed. First, bacteria can be easily combined with other organic compounds without pure water. Second, bacterial engines only need simple nutrients, such as glucose. They are very sensitive to their surroundings, meaning they can be precisely controlled with chemicals.

"In the future, such hybrids could be used to deliver drugs to parts of the body, such as urinary tract, eye sockets, ears ," Sitti said. 'They can also be used to monitor harmful biochemical agents in the environment, inspect and maintain tubes containing liquids in spacecraft and nuclear plants'.

Viet Linh