Tiny power generators take a leaf out of plants' book

SCIENTISTS have built tiny machines which mimic the way in which plants turn light into energy - and so could become the power generators of a 21st-century industry using microscopic machines.

"The only limit on the applications is imagination," said Thomas Moore of Arizona State University, who worked on the experiment reported today in the science journal Nature. "It's like 120 years ago when Thomas Edison realised they could generate electricity, laid the wires into the city and said 'What you do with it is up to you.' This takes that down to the molecular level."

The devices, built at Arizona State University, employ the same basic mechanism as plants: they use the energy from photons of light to "push" positively charged hydrogen ions across a membrane, after which the ions "fall" back to their starting point like a river flowing over a water wheel. The movement of the "water wheel" turns a protein complex into the universal unit of cellular energy, the adenosine triphosphate (ATP) molecule.

The artificial system is 235 times smaller and simpler than its biological protein equivalent. Its overall efficiency is about 4 per cent, though the researchers view that as a starting point rather than an upper limit.

The most obvious use for such a power plant would be in "nanotechnology" systems, where mechanical systems may be so tiny that hundreds of them can fit onto the head of a pin. Possible applications include medical systems which could monitor the body from inside, or generate pharmaceuticals on industrial levels.

"Nanotechnology is exactly what this is for," said Professor Moore. "You could have a biochemical reaction which produces a useful drug: that would be powered by ATP. All you need is solar radiation."