Mapping the Young's modulus distribution of the human tympanic membrane by microindentation

The human tympanic membrane (TM, or eardrum) is composed primarily of layers of collagen fibers oriented in the radial and circumferential directions, as well as epidermal and mucosal layers at the lateral and medial surfaces. The mechanical properties of the TM depend on the microstructures of the...

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Bibliographic Details
Published in:Hearing research 2019-07, Vol.378, p.75-91
Main Authors: Luo, Huiyang, Wang, Fang, Cheng, Chen, Nakmali, Don U., Gan, Rong Z., Lu, Hongbing
Format: Article
Language:English
Subjects:
Aged
Aged, 80 and over
Biomechanical Phenomena
Cadaver
Elastic Modulus
Elasticity Imaging Techniques
Female
Fibrillar Collagens - physiology
Human tympanic membrane
Humans
Male
Microindentation
Middle Aged
Models, Biological
Models, Statistical
Modulus map
Nanotechnology
Statistical analysis
Tympanic Membrane - diagnostic imaging
Tympanic Membrane - physiology
Viscoelastic
Young's modulus
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Summary:The human tympanic membrane (TM, or eardrum) is composed primarily of layers of collagen fibers oriented in the radial and circumferential directions, as well as epidermal and mucosal layers at the lateral and medial surfaces. The mechanical properties of the TM depend on the microstructures of the collagen fibers, which vary with location, resulting in a spatial variation of Young's modulus. In this study, the Young's modulus of the human TM is measured using microindentation. A 10 μm diameter spherical nanoindenter tip is used to indent the TM at different locations in the lateral and medial surfaces. Through a viscoelastic contact analysis, the steady state out-of-plane (through thickness) Young's modulus at a constant strain rate for the TM is determined from the uniaxial relaxation modulus. The measured spatial distribution of Young's modulus is reported for the entire TM pars tensa on both lateral and medial surfaces. The Young's modulus, for the four TM quadrants, is analyzed statistically using a normal quantile-quantile (Q-Q) plot. The obtained S-shaped curve indicates a bi-modal Gaussian distribution in the Q-Q plot. The spatial distribution of the Young's modulus is modeled by a bivariate Gaussian function in the polar coordinates over the entire TM on both the lateral and medial surfaces. It is shown that the anterior-superior quadrant has the smallest value of Young's modulus. Differences are observed in the spatial distribution of the Young's modulus for both the lateral and medial surfaces. For the medial surface, Young's modulus varies mainly along the radial direction following a small-large-small trend, emanating from the umbo. For the lateral surface, the modulus at the anterior-superior quadrant shows the smallest modulus; the modulus decreases gradually along the radial directions. The quantitative results presented in this paper will help improve future simulation models of the middle ear by using spatial dependence of Young's modulus over the entire TM. •Microindentation was used to measure the out-of-plane Young's modulus of the entire human TM.•The Young's modulus distribution is reported for the entire TM pars tensa on both lateral and medial sides.•The Young's modulus mapping was accurately modeled by a bivariate Gaussian function in polar coordinates.
ISSN:0378-5955
1878-5891
DOI:10.1016/j.heares.2019.02.009