Applied Physics

Listening In by Nanoparticle

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Science  27 Jan 2012:
Vol. 335, Issue 6067, pp. 381
DOI: 10.1126/science.335.6067.381-a

The degree of control with which particles can be trapped, rotated, pulled apart, and manipulated by focused light beams has made optical tweezers an extremely useful laboratory tool across many disciplines—from probing the mechanical properties of cells and DNA to building three-dimensional structures and cooling gases to their quantum ground state. It might be expected that external perturbation or excitement would produce a wobble of a light-trapped particle. Ohlinger et al. exploit this effect to show that a trapped gold nanoparticle can be used as an ultrasensitive detector of sound waves. A typical empty room has a sound level of 20 decibels. By comparison, the trapped gold nanoparticle can detect sounds down to −60 decibels—over six orders of magnitude more sensitive than the human ear. The authors suggest that such enhanced sensitivity could be used to probe live bacteria and cells that produce acoustic vibrations but are not easily seen with optical microscopes.

Phys. Rev. Lett. 108, 18101 (2012).

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