Characterising soft tissues under large amplitude oscillatory shear and combined loading

Area of Science:

• Biomaterials Science
• Soft Matter Physics
• Tissue Mechanics

Background:

• Characterizing soft biological tissues beyond linear viscoelasticity is difficult due to complex behaviors.
• Tissue viscoelastic properties vary significantly with sample preparation and loading, leading to inconsistent literature data.
• Existing methods struggle to accurately capture the non-linear mechanical responses of biological tissues.

Purpose of the Study:

• To develop and validate a novel technique for characterizing non-linear viscoelastic behavior in soft biological tissues.
• To investigate the influence of preload on tissue mechanical properties under shear testing.
• To correlate micro-structural changes with observed viscoelastic responses during large amplitude oscillatory shear (LAOS).

Main Methods:

• Utilized Fourier Transformation to decompose stress output waveforms into harmonic contributions under LAOS.
• Applied varying preload (compressive strain) to liver tissue specimens before shear testing.
• Performed histological analysis to examine tissue micro-structure after mechanical testing.

Main Results:

• The novel Fourier Transform method efficiently characterized non-linear tissue behavior under LAOS.
• Preload significantly affected the linear viscoelastic response of liver tissue, correlating with observed structural changes.
• Changes in the third harmonic component of shear moduli at 50% shear strain were linked to alterations in sinusoid micro-structure.

Conclusions:

• Fourier analysis provides an effective means to characterize the non-linear viscoelasticity of soft tissues.
• Preload influences tissue mechanics and micro-structure, highlighting the importance of standardized sample preparation.
• The study demonstrates a robust method for assessing soft tissue behavior under combined loading conditions.