APPLIED PHYSICS: Vapors Plucked on a Harp

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Science  07 Mar 2008:
Vol. 319, Issue 5868, pp. 1311a
DOI: 10.1126/science.319.5868.1311a

Optical or electronic devices that sniff out chemical compounds with high sensitivity and selectivity clearly have applications in a broad range of circumstances, from environmental monitoring to the detection of biohazards. However, the compounds of interest may not be in pure form; often they are diluted among multiple background substances, and such an artificial nose must therefore be able to sort through complex mixtures. Stievater et al. present a chemical sensor based on a micro-optomechanical bridge that can be interrogated remotely using optics. Their device, a microharp, forms one end of a Fabry-Perot interferometer and comprises an array of microbridges in which each bridge is coated with a sorbent polymer sensitive to a particular analyte. Each bridge also has a distinct length and so vibrates at an individual frequency. When the device is placed in a test atmosphere, different compounds bind to particular strings on the harp, changing the mass of the bridge and thereby inducing a shift in the frequency at which it vibrates. Interrogating the vibrational frequency of each bridge separately allows monitoring of a vapor's chemical composition remotely, and in some cases (as for organophosphonates) detection concentrations down to 17 parts per billion. — ISO

Opt. Express 16, 2423 (2008).

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