14 DAY TRIAL // The experiment involving tiny metal rods are the first non-biological entities to show a behavior similar to that of tiny organisms such as bacteria that propel themselves towards different areas by following a chemical signature. The process is called chemotaxis. This experiment could have potential applications from detecting chemicals to assembling tiny structures.
Chemotaxis represents a tendency of biological organisms to move towards or away from certain chemicals. This process can be successfully applied to non-biological systems, to direct the motion of particles in fluids or to assemble them into nanostructures without the use of traditional electric or magnetic fields. This can also be used to seek out for chemicals in environments that are hostile for life.
Though the tiny metal rods seemed to mimic some of the biological characteristics of the bacteria, the process taking place in living organisms is much more complicated. Researchers at the Pennsylvania State University used a large number of tiny metal rods 2 ?m long; each was made out of gold along one half and platinum along the other half.
The rods were placed in a dish containing pure water and a piece of gel containing hydrogen peroxide. The hydrogen peroxide leached away from the gel into the water. After 110 hours, the team of researchers noticed that 70 percent of the rods moved next to the gel.
This happened as a result of the reaction between the hydrogen peroxide and the gold and platinum at each end of the rods. The reaction determines the surrounding fluid to move along the rod driving it towards the gel. As the concentration of the hydrogen peroxide is greater, the speed of the moving particles increases, causing the metal rods to attach to the gel.
Ayusman Sen of the Pennsylvania State University said that this experiment proves the possibility of building nanoscale motors that mimic biological motor capabilities, from scratch. The team is now studying the use of light to mimic "photoaxis", a phenomenon in which organisms move by orientating towards the sources of light.
