Resilient Mechanical Metamaterial Based on Cellulose Nanopaper with Kirigami Structure

Area of Science:

• Materials Science
• Mechanical Engineering
• Polymer Science

Background:

• Cellulose nanofiber (CNF) nanopapers exhibit bending flexibility but lack stretching capabilities, limiting their use in flexible devices.
• Kirigami structures can enhance the stretching flexibility of nanopapers, but their mechanical resilience under repeated stretching remains unexplored.

Purpose of the Study:

• To investigate the mechanical resilience of CNF nanopapers with Kirigami structures under iterative tensile loading.
• To determine the influence of cut pattern edge geometry on the stretching resilience of these engineered nanopapers.

Main Methods:

• Fabrication of cellulose nanopapers with integrated Kirigami structures.
• Experimental evaluation using iterative tensile tests with large strain amplitudes.
• Comparative analysis of nanopapers with sharp versus rounded cut pattern edges.

Main Results:

• Nanopapers with Kirigami structures demonstrate significant stretching flexibility.
• Mechanical resilience is maintained for moderate maximum strains, though residual strain increases with strain magnitude and cycling.
• Rounded edges of Kirigami cut patterns substantially improve mechanical resilience under harsh stretching conditions.

Conclusions:

• Kirigami-based designs enhance the stretching flexibility of cellulose nanopapers.
• Optimizing cut pattern geometry, specifically using rounded edges, is critical for improving mechanical resilience and preventing fracture.
• Relaxing stress concentration is key for both fracture prevention and achieving robust mechanical resilience in flexible nanopaper applications.