Needle insertion-induced quasiperiodic cone cracks in hydrogel.

Area of Science:

• Materials Science
• Biomedical Engineering
• Fracture Mechanics

Background:

• Needle insertion in minimally invasive surgery can cause significant, yet poorly understood, tissue damage.
• The opaque and inhomogeneous nature of biological tissues hinders direct observation of damage mechanisms.
• Developing tissue mimics is crucial for studying these intricate processes.

Purpose of the Study:

• To investigate needle insertion-induced damage mechanisms using a transparent tissue mimic.
• To analyze the forces and crack propagation during needle penetration.
• To understand the role of stress fields in crack formation and periodicity.

Main Methods:

• Utilizing transparent and homogeneous polyacrylamide hydrogel as a tissue mimic.
• Recording insertion forces and needle displacement during penetration.
• Observing and characterizing the resulting crack patterns within the hydrogel.

Main Results:

• Insertion force exhibited a pattern of gradual increase followed by a sharp fall, correlating with crack propagation.
• The study documented the first observation of nearly periodic, stable, three-dimensional cone cracks during deep needle penetration.
• The stress field around the needle tip was identified as the cause of crack symmetry and periodicity.

Conclusions:

• Polyacrylamide hydrogel serves as an effective model for studying soft, brittle material fracture.
• Understanding these fracture dynamics provides insights into controlling tissue damage during surgical needle insertion.
• The findings offer a promising direction for improved needle designs and surgical techniques.