PhD defense

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Powerpoint presentation of my public PhD defense, held on September 24, 2012.

Title: Mechanical properties of the tympanic membrane - Measurement and modeling

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  • Fysicahoudt in: beschrijvennatuurfenomenen, maar ookgebruik van die kennisvoortechnologischeontwikkelingen
  • Fysicahoudt in: beschrijvennatuurfenomenen, maar ookgebruik van die kennisvoortechnologischeontwikkelingen
  • Ookligamenten en spiertjes, niet in de figuur
  • Geenperfecteimpedantie-matching!!!
  • Geenperfecteimpedantie-matching!!!
  • Geenperfecteimpedantie-matching!!!
  • Vanaf nu hier en daarnogaltechnisch/theoretisch, maar duidelijklatenblijkenwanneerikbijvolgende punt komen
  • Vanaf nu hier en daarnogaltechnisch/theoretisch, maar duidelijklatenblijkenwanneerikbijvolgende punt komen
  • Vanaf nu hier en daarnogaltechnisch/theoretisch, maar duidelijklatenblijkenwanneerikbijvolgende punt komen
  • Vanaf nu hier en daarnogaltechnisch/theoretisch, maar duidelijklatenblijkenwanneerikbijvolgende punt komen
  • Doe je daarvijfjaar over? Zeggennogmeergedaan!
  • PhD defense

    1. 1. Mechanical Properties of the TympanicMembrane: Measurement and ModelingJef AernoutsLaboratory of Biomedical Physics (BIMEF)University of AntwerpPhD defenseSeptember 24th, 2012
    2. 2. A PhD study• PhD: Doctor of Philosophy - “philosophy” = “love of wisdom”• PhD in Physics - “to understand the behavior of natural phenomena…” 1
    3. 3. A PhD study• PhD: Doctor of Philosophy - “philosophy” = “love of wisdom”• PhD in Physics - “to understand the behavior of natural phenomena… …and to use this knowledge for new technologies” 2
    4. 4. Mechanical Properties of the TympanicMembrane: Measurement and Modeling 3
    5. 5. Mechanical Properties of the TympanicMembrane: Measurement and Modeling 4
    6. 6. The human ear tympanic membrane 5
    7. 7. Middle ear & tympanic membrane 6
    8. 8. Function of the earConvert sound (20-20000 Hz) > nerve activity in our brain What is role middle ear? 7
    9. 9. Role of the middle ear Impedance matching air between air & fluid fluid ? 8
    10. 10. Middle ear impedance matching1. Area ratio 9
    11. 11. Middle ear impedance matching1. Area ratio2. Lever action 10
    12. 12. Middle ear impedance matching1. Area ratio2. Lever action3. „Buckling effect‟ 11
    13. 13. Mechanical Properties of the TympanicMembrane: Measurement and Modeling 12
    14. 14. Mechanics• “Behavior of solids when subjected to forces” Elasticity linear visco-elastic stress F/A non-linear steel rubber biological strain tissue l/l 13
    15. 15. Mechanics• “Behavior of solids when subjected to forces” Vibrational mechanics 100 Hz (deformation x1e4) 5000 Hz (deformation x4e6) 14
    16. 16. Why study TM mechanics?• Middle ear finite element modeling tympanic membrane! normal(Aerts J, Aernouts J. 2012) reconstructed diseased (Kelly et al., 2003) (Gan et al., 2009) 15
    17. 17. Mechanical Properties of the TympanicMembrane: Measurement and Modeling 16
    18. 18. Mechanical Properties of the Tympanic Membrane: Measurement and Modeling1. Validation measurements and modeling2. Gerbil tympanic membrane pars tensa elasticity3. Gerbil tympanic membrane pars flaccida elasticity4. Human tympanic membrane elasticity5. Human tympanic membrane vibrations 17
    19. 19. Mechanical Properties of the Tympanic Membrane: Measurement and Modeling1. Validation measurements and modeling2. Gerbil tympanic membrane pars tensa elasticity3. Gerbil tympanic membrane pars flaccida elasticity4. Human tympanic membrane elasticity5. Human tympanic membrane vibrations 18
    20. 20. Mechanical Properties of the Tympanic Membrane: Measurement and Modeling1. Validation measurements and modeling2. Gerbil tympanic membrane pars tensa elasticity3. Gerbil tympanic membrane pars flaccida elasticity4. Human tympanic membrane elasticity5. Human tympanic membrane vibrations 19
    21. 21. Human tympanic membrane- Base diameter: 9 mm- Apex height: 1.7 mm 20
    22. 22. TM elasticity• Literature: experiments on cut-out strips - Erroneous analyses (non-uniform thickness) - Difficult specimen clamping• In my work: experiments on intact samples 21
    23. 23. Needle indentation• Approach - Apply indentations - Measure forces (1) TM, (2): force transducer, (3): piston, (4): LVDT , (5): signal generator, (6): feedback control unit 22
    24. 24. Needle indentation• Approach - Apply indentations - Measure forces• Sample preparation 23
    25. 25. Needle indentation• Approach - Apply indentations - Measure forces• Sample preparation• Results - Quasi-static 24
    26. 26. Needle indentation• Approach - Apply indentations - Measure forces• Sample preparation• Results - Quasi-static - Step 25
    27. 27. monitor camera vaporizer samplemounterattachedto loadcell piston that drives needle LVDT
    28. 28. Shape measurement• Moiré profilometry Buytaert JAN, Dirckx JJJ. Phase-shifting Moiré topography using optical demodulation on liquid crystal matrices. Optics and Lasers in Engineering. 2010;48(2):172–181. 27
    29. 29. Shape measurement• Moiré profilometry Buytaert JAN, Dirckx JJJ. Phase-shifting Moiré topography using optical demodulation on liquid crystal matrices. Optics and Lasers in Engineering. 2010;48(2):172–181. 28
    30. 30. Finite element model1. Import geometry 29
    31. 31. Finite element model1. Import geometry2. Mesh geometry 30
    32. 32. Finite element model In rest1. Import geometry2. Mesh geometry3. Apply loadings & boundary conditions Indented 31
    33. 33. Finite element model1. Import geometry2. Mesh geometry3. Apply loadings & boundary conditions4. Quasi-static stiffness: E = (2.9±1.3) MPa 32
    34. 34. Visco-elastic properties• Relaxation function in time domain 33
    35. 35. Visco-elastic properties• Relaxation function in time domain  frequency domain 34
    36. 36. Mechanical Properties of the Tympanic Membrane: Measurement and Modeling1. Validation measurements and modeling2. Gerbil tympanic membrane pars tensa elasticity3. Gerbil tympanic membrane pars flaccida elasticity4. Human tympanic membrane elasticity5. Human tympanic membrane vibrations 35
    37. 37. Work at Boston 36
    38. 38. TM mechanics at acoustic freqs• Sample 37
    39. 39. TM mechanics at acoustic freqs front view• Sample• Laser Doppler vibrometry - Sounds: 100 Hz – 18 kHz, 80-120 dB - Umbo velocity 38
    40. 40. TM mechanics at acoustic freqs• Sample• Laser Doppler vibrometry - Sounds: 100 Hz – 18 kHz, 80-120 dB - Umbo velocity• Stroboscopic holography - Sounds: 0.5 kHz – 19 kHz, 80-120 dB - Full-field displacement 39
    41. 41. Holography• Principle• Digital holography - CCD - Virtual reconstruction: hologram before and after > deformation CCD 40
    42. 42. Stroboscopic holography• Shutter laser beam/ pulsed laser on specific phases• Both magnitude and phase of vibration pattern 41
    43. 43. probe microphone speaker holography setupsample camera
    44. 44. FE model• Geometry (from micro-CT) (Aerts Johan, 2012) 43
    45. 45. FE model• Geometry (from micro-CT)• Boundary conditions & Loadings sound wave 44
    46. 46. TM transfer function- Measured with laser Doppler vibrometry: 45
    47. 47. TM transfer function- Measured with laser Doppler vibrometry:- Finite element model outcome 46
    48. 48. TM full-field displacement- Measured with stroboscopic holography: 47
    49. 49. TM full-field displacement- Measured with stroboscopic holography:- Finite element outcome 48
    50. 50. TM wave motion 1000 Hz(deformation x6e3) 7000 Hz (deformation x1e5) 16000 Hz(deformation x8e5) 49
    51. 51. TM curvature• Cochlear load at umbo (tip malleus)• Natural curved versus artificially flat 50
    52. 52. TM curvature 800 Hz – 4 kHz:• Umbo velocity response 17.5 dB difference 51
    53. 53. General conclusion• Indentation approach - Quasi-static regime (0.001 Hz – 3 Hz) - Elastic characterization pars tensa• Static inflation experiments - Elastic characterization pars flaccida• Stroboscopic holography - Acoustic regime (20 Hz – 20 kHz) - Vibrational properties tympanic membrane 52
    54. 54. Thanks for your attention!• Questions? I‟m all ears… 53

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