Enhanced Rupture Force in a Cut-Dispersed Double-Network Hydrogel

Area of Science:

• Materials Science
• Mechanical Engineering
• Polymer Science

Background:

• Kirigami, the art of paper cutting, offers a method for controllable material deformation.
• Cuts in materials, typically defects, often degrade mechanical properties.
• Tough double network (DN) hydrogels combine rigid and ductile networks for enhanced properties.

Purpose of the Study:

• To investigate the influence of dispersed macro-scale cuts on the mechanical properties of DN hydrogels.
• To compare the fracture behavior of DN gels with dispersed cuts (D-cut gel) versus continuous cuts (C-cut gel).
• To elucidate the fracture mechanism in kirigami-cut soft materials.

Main Methods:

• Fabrication of D-cut gels with dispersed cuts and C-cut gels with continuous cuts.
• Performing fracture tests on both D-cut and C-cut gels with varying cut patterns.
• Utilizing homemade circular polarizing optical systems for stress analysis.

Main Results:

• Crack blunting observed at each cut tip in D-cut gels.
• Formation of a large wrinkle-like zone parallel to cut propagation.
• Dispersed cuts increased rupture force by homogenizing stress and reducing stress concentration.
• C-cut gels exhibited different fracture behaviors compared to D-cut gels.

Conclusions:

• Kirigami-inspired dispersed cuts enhance the toughness and rupture force of DN hydrogels.
• Stress homogenization around multiple cut tips is the key mechanism for improved mechanical performance.
• This study provides insights into the fracture mechanics of kirigami-cut soft materials.
• Findings can guide the design of advanced, soft, and tough materials.