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The Micromechanics Group in the Research Lab of Electronics at MIT carries out fundamental research on the the mechanical properties of both biological and man-made microscopic structures, including the inner ear and MEMS devices. The goals of this research are to provide insight into basic mechanisms underlying hearing, to improve techniques for characterizing MEMS, and to develop a better understanding of micromechanics to allow for the design of more sophisticated microscopic structures. dedicated to investigating the mechanical properties and interactions of micro-scale structures, particularly those with biological significance. One of the group's key interests is the cochlea, which is the organ responsible for our sense of hearing. A vast array of moving parts interact to convey sound to the hair cells of the cochlea. Understanding these interactions is critical for designing next-generation assistive listening devices.


We have recently shown that, like the basilar membrane (BM) of the cochlea, the tectorial membrane (TM) supports longitudinally propagating traveling waves. Unlike BM waves, however, TM waves are radial shear waves that can directly excite the hair bundles of sensory hair cells. The existence of this new class of wave, coupled with the known importance of the TM for hearing, suggests that the interaction of BM and TM traveling waves gives rise to the sensitivity and frequency selectivity of hearing. MIT has issued a press release describing this new finding, including videos of TM wave motion that have been magnified to make the motion visible.

Our paper describing this result, Longitudinally propagating traveling waves of the mammalian tectorial membrane, was recently published in Proceedings of the National Academy of Sciences of the USA (link goes to abstract). A PDF version of the paper is available at the link below.

Ghaffari, Aranyosi and Freeman, PNAS 104:16510-16515, 2007.