17 Jun 2002
Pulses of violet and ultraviolet light drive a molecular machine.
A single molecule powered by light has performed mechanical work for the first time.
Hermann Gaub of Ludwig-Maximilians University in Munich, Germany, and colleagues made a single polymer molecule stretch and contract by shining light on it. (Science 296 1103).
The technique could power molecular machines of the future. These nano-scale devices hold much promise for future applications in electronics, medicine and communications, but a major challenge lies in finding a suitable power source.
Gaub's group has shown that light can power mechanical transitions in an azobenzene polymer.
Chemists have long known that this molecule can be switched between its long (trans) and short (cis) states by illuminating it with light of certain wavelengths, and the effect is exploited in many bulk chemical processes. This latest result shows that the effect can also be useful at the single-molecule level.
After illuminating the sample with five pulses of 420 nm light, the cis molecule flipped into the trans state, stretching by 1.4 nm. When Gaub's team subsequently fired a sequence of 365 nm pulses onto the polymer, the molecule contracted back into the cis form.
Although the process is currently rather inefficient, the team is optimistic that it can be improved so that the system could operate in a real device.