Light Drives Mechanical Work
26 June 2008, 12:48
Categories: smt-polymorphic-shape-shifters smart-materials-smt
Smart materials that change shape in response to external stimuli form the basis of modern devices, and, in turn, have recently stimulated the imagination of many designers. But identifying materials that convert an input stimulus to mechanical work has been of long standing interest. There are some outstanding examples: the description of the pyroelectric effect in tourmaline by Theophrastus in 314 BC; the observation of piezoelectricity by Pierre and Jacques Curie in 1880; and the development of the bimetallic strip by John Harrison in the 1700s to measure nautical time.
Recently, researchers have shown a growing interest in the use of light (photons from lasers) as the energy input for stimulating materials. In the conversion of light to mechanical work, photons are emitted by a light source and are absorbed by a photoactive material that may produce mechanical motion, either by: (a) a reversible conformational change, or (b) a local temperature increase. When these molecular processes are amplified to macroscopic shape or volume changes, mechanical work or motion can be integrated into a range of remotely controlled devices, such as beam stirring mirrors or robots.
One of the first realizations of this idea was by Uchino in 1989, who demonstrated photostriction of PLZT (lanthanum modified lead zirconate titanate) with the intent to drive robots remotely in a non-contact, wireless mode. In contrast to thermal, electrical, or chemical approaches, a coherent and wavelength-specific photon flux enables facile ‘remote’ control of the process, as well as precise spatial localization.
Posted by: The Editors
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