Soft-solid deformation mechanics at the tip of an embedded needle

Area of Science:

• Materials Science
• Soft Matter Physics
• Solid Mechanics

Background:

• A novel technique measures soft material properties using an embedded needle.
• Previous models used simplified spherical approximations, ignoring stress concentrations.

Purpose of the Study:

• To investigate void growth mechanics in neo-Hookean materials under needle indentation.
• To evaluate the effectiveness of different deformation parameters for modeling needle-mediated void growth.

Main Methods:

• Theoretical analysis of elasticity- and surface tension-governed void growth.
• Comparison of a spherical void model with needle-mediated growth data.
• Utilizing areal surface stretch ratio as a key deformation parameter.

Main Results:

• Needle-mediated void growth exhibits inhomogeneities.
• The areal surface stretch ratio provides a robust deformation parameter.
• Good agreement is achieved between spherical void and needle geometries using this parameter.

Conclusions:

• The areal surface stretch ratio accurately captures the essential deformation in needle-mediated void growth.
• This finding validates the use of simplified models for analyzing complex soft material behaviors.
• The study refines the understanding of soft material characterization techniques.