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Static versus dynamic gerbil tympanic membrane elasticity: derivation of the complex modulus
Jef Aernouts1, Joris J J Dirckx
1Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium. jef.aernouts@ua.ac.be
Biomechanics and Modeling in Mechanobiology
|November 1, 2011
Summary
Tympanic membrane stiffness increases with indentation frequency. This study measured gerbil tympanic membrane mechanical behavior under quasi-static and dynamic loading, revealing frequency-dependent stiffness crucial for middle ear models.
Area of Science:
- Biomechanics
- Otolaryngology
- Materials Science
Background:
- Accurate tympanic membrane stiffness estimation is vital for realistic middle ear mechanics modeling.
- Biological tissues exhibit strain rate sensitivity, necessitating investigation under varied loading conditions.
- Previous studies primarily focused on quasi-static or dynamic loading of the tympanic membrane.
Purpose of the Study:
- To investigate the mechanical behavior of the tympanic membrane under both quasi-static and dynamic loading conditions.
- To determine the frequency-dependent Young's modulus of the tympanic membrane.
- To provide data for improved computational models of middle ear mechanics.
Main Methods:
- Experiments conducted on gerbil tympanic membranes (pars tensa).
- Custom-built apparatus for in situ indentation testing with quasi-static and dynamic sinusoidal loads up to 8.2 Hz.
- Specimen-specific finite element models created using measured unloaded shapes to simulate experiments; inverse analysis used to estimate frequency-dependent Young's modulus.
Main Results:
- Young's moduli ranged from 71 to 106 MPa (n=4) at 0.2 Hz indentation frequency for an 8 μm central region thickness.
- A 14% average relative increase in modulus was observed within the tested frequency domain (up to 8.2 Hz).
- The modulus increase was most pronounced below 6 Hz, indicating significant viscoelastic behavior.
Conclusions:
- The tympanic membrane exhibits frequency-dependent stiffness, with modulus increasing at higher indentation frequencies.
- Viscoelastic models (standard linear and continuous relaxation spectrum) effectively describe the complex modulus.
- Findings highlight the importance of considering dynamic loading effects for accurate tympanic membrane mechanical characterization.
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