How to test very soft biological tissues in extension?

Area of Science:

• Biomechanics
• Materials Science
• Medical Engineering

Background:

• Soft tissues like brain and liver have largely been unstudied due to lack of mechanical load-bearing.
• Advancements in surgical robotics and virtual reality necessitate understanding soft tissue mechanical properties.
• Existing research relies on compression, indentation, and impact tests, lacking tensile data.

Purpose of the Study:

• To present an analytical solution for relating machine head displacement to strain in soft tissue tensile tests.
• To enable more accurate mathematical modeling of soft tissues for engineering applications.
• To address the gap in tensile testing data for soft biological tissues.

Main Methods:

• Developed a theoretical solution for uniaxial extension of cylindrical samples.
• The solution is valid for isotropic, incompressible materials with moderate deformations (<30%).
• Assumed that planes initially perpendicular to the extension direction remain plane.

Main Results:

• The deformed shape of a uniaxially extended cylindrical sample is independent of the constitutive law.
• Vertical extension in the plane of symmetry is proportional to total height change for strains up to 30%.
• Provides a method to analyze tensile test data from soft tissues.

Conclusions:

• The presented analytical solution is vital for accurate soft tissue characterization.
• Enables reliable tensile testing, previously unavailable for soft tissues.
• Results have significant implications for biomechanics, surgical simulation, and robotic surgery.