German researchers demonstrate light-driven nanoscale mechanism

Mr_Farlops writes "German researchers have developed a simple method to turn light into mechanical energy on the molecular scale. By shining light of one frenquency on an azobenzene molecule, they caused it to crimp and contract, pulling a load. By switching to another frequency, they caused the molecule to relax and stretch, releasing the tension."

Read more for details, links to web reports, and information on other research that indicates lasers can also be used to generate rotary motion in carbon nanotubes. This post refers to work reported by Hermann Gaub of Ludwig-Maximilians University in Munich and colleagues in the 10 May 2002 issue of Science, in which the researchers obtained mechanical work from a single molecule for the first time when they made an azobenzene polymer molecule stretch and contract by shining light on it. A cantilever attached to the molecule measured the forces exerted during this cycle, which was repeated several times before the molecule broke. The articleís abstract provides a good summary of the significance of the research:

Light-powered molecular machines are conjectured to be essential constituents of future nanoscale devices. As a model for such systems, we have synthesized a polymer of bistable photosensitive azobenzenes. Individual polymers were investigated by single-molecule force spectroscopy in combination with optical excitation in total internal reflection. We were able to optically lengthen and contract individual polymers by switching the azo groups between their trans and cis configurations. The polymer was found to contract against an external force acting along the polymer backbone, thus delivering mechanical work. As a proof of principle, the polymer was operated in a periodic mode, demonstrating for the first time optomechanical energy conversion in a single-molecule device.

Additional coverage of the research

Those interested in this item may also be interested in a UPI article ("Lasers may power nano-motors", by Mike Martin, 23 April 2002), which describes work by researchers at Harvard University and the Weizmann Science Institute in Israel that demonstrated infrared laser light can be used to transfer angular momentum to carbon nanotubes. "We are able to show that light can spin nanotubes with ultra-high frequencies," Weizmann Institute chemical physicist Petr Kral said in a recent paper from Rehovot, Israel.

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