Measurement of mechanical impedance

Set-up for measuring the mechanical impedance of the

organ of Corti. The sample consists of one half of a cochlear turn. The tectorial membrane is removed and the preparation (yellow and light blue) placed on a support (tourquoise) in such a way that the basilar membrane is lying flat on the support. The (atomic force) cantilever (black), with its tip in contact with the upper surface of the organ of Corti (light blue), was used to determine the impedance of the organ at the contact point. The cantilever carries a hard magnetic coating with a permanent magnetic moment. A time harmonic magnetic field, generated by a coil below the preparation, delivers a calibrated harmonic dipole force to the cantilever. The resulting velocity of the cantilever at the contact point is measured with a laser Doppler vibrometer (not shown). The mechanical impedance of the organ is then derived from the difference in velocities between measurements with and without contact to the preparation.
© 2005 A. W. Gummer. Animation by Dr. M. P. Scherer.