STRC Research

tectorial-membrane

3 min read

Tectorial membrane mechanics — validated parameters

Source agent: h02 parameter provenance audit (Sonnet 4.6), 2026-04-23. Consumer: piezo_voltage_budget.py, piezo_phase2_frequency_bundle.py.

Structural parameters

ParameterValueSourceConditionsStatusNotes
TM thickness (mouse, apical)~30–50 µmestimate from human data—⚠Human TM thickness 19 µm (hook) to 64 µm (upper middle) per Masaki 2009 (PLOS One, search result). Mouse TM thinner. NEEDS primary murine measurement.
TM Young’s modulus (apical HC zone)24 ± 4 kPaMasaki 2009 PLOS One (AFM indentation)mouse TM, apical⚠ NEEDS PDFRadial gradient: 24 kPa apical → 210 kPa basal.
TM Young’s modulus (basal HC zone)210 ± 15 kPaMasaki 2009 PLOS Onemouse TM, basal⚠ NEEDS PDFOrder-of-magnitude stiffer than apical.
TM shear storage modulusfrequency-dependentGhaffari 2007 PNAS 104:16510isolated mouse TM segments⚠ NEEDS PDFGhaffari measured traveling wave propagation to extract dynamic shear modulus. Key paper for TM mechanics.
TM water content~97%established—✅ referenceTM is essentially a hydrogel; determines poroelastic behavior.
TM collagen fibrils~1 µm diameter radial fibersMasaki 2009; Gavara/Chadwickmouse✅Source of radial mechanical anisotropy; relevant to conformal film deposition direction.

TM displacement vs SPL

These values are used in TM_DISP_60dB dict in piezo_phase2_frequency_bundle.py. Scripts cite “Gueta 2006, Ren 2011” without page/figure.

FrequencyValue (60 dB SPL)SourceStatusNotes
200 Hz30 nmscripts claim Gueta 2006 / Ren 2011⚠ NEEDS VERIFICATIONTM displacement at low frequencies is large relative to base. Plausible but unverified.
1000 Hz20 nmscripts claim Gueta 2006 / Ren 2011⚠ NEEDS VERIFICATION—
4000 Hz10 nmscripts claim Gueta 2006 / Ren 2011⚠ NEEDS VERIFICATIONConsistent with 5–30 nm range reported in literature.
8000 Hz5 nmscripts claim Gueta 2006 / Ren 2011⚠ NEEDS VERIFICATION—

Context: The 5–30 nm at 60 dB SPL range is broadly consistent with published in vivo TM measurements (Ren 2002, Gao 2014 OCT, Ghaffari 2007 ex vivo). The script’s CF-dependent scaling (30 nm at 200 Hz, 5 nm at 8 kHz) is physically motivated — apical regions move more at lower frequencies. However, “Gueta 2006” appears to be Gueta et al. (2008) Biophys J paper on OHC stereocilia deflection from TM anisotropy, not a direct TM displacement measurement. The citations need verification.

Papers to retrieve for this topic

PriorityPaperWhat it provides
P1Ghaffari R et al. (2007) PNAS 104:16510TM shear modulus, traveling wave propagation — foundational TM mechanics
P1Masaki K et al. (2009) PLOS One 4:e4877TM Young’s modulus (24–210 kPa), radial collagen anisotropy
P2Gueta R et al. (2008) Biophys J 95:4948OHC stereocilia deflection from TM anisotropy — verify whether it reports absolute displacement values
P2Ren T (2002) Nat Neurosci 5:169BM traveling wave propagation — not TM displacement directly; check for TM data
P3Gao SS et al. (2014) Biophys JOCT-based TM/BM displacement — more recent and direct

Relevance to h02 piezo hypothesis

The TM is the proposed substrate for PVDF-TrFE film deposition. Critical parameters for hypothesis feasibility:

  1. TM stiffness (24–210 kPa) is orders of magnitude softer than PVDF-TrFE (3 GPa). The film will not load-couple efficiently to the TM — the film is ~10⁵× stiffer than the substrate. This mechanical mismatch may severely reduce actual strain delivered to the film vs. the model assumption. This is a potential hypothesis-level mechanical flaw not currently modeled in any piezo script.

  2. TM surface topology: radially-oriented collagen fibers provide directionality. A conformal film would need to deposit along the radial axis to use TM displacement most efficiently.

  3. TM displacement magnitudes (5–30 nm at 60 dB) are the mechanical input to the piezo model. These are the most uncertain values in the chain.

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