A Gradient-Softening Strategy in Hydrogel Films to Optimize Balance between Interfacial Toughness and Structural...

Area of Science:

• Materials Science
• Polymer Science
• Mechanical Engineering

Background:

• Flexible hydrogel films are crucial for wearable devices and electronics.
• Existing hydrogels face a trade-off between peel resistance and structural integrity.
• Traditional methods like surface modification cannot resolve this inherent limitation.

Purpose of the Study:

• To propose and validate a gradient-softening strategy for hydrogel films.
• To address the bottleneck of poor interfacial peel resistance and structural integrity.
• To enhance the performance of hydrogel films for flexible electronics.

Main Methods:

• Fabrication of hydrogel films with a through-thickness decreasing modulus gradient.
• Adjustment of cross-linker and water content to control mechanical properties.
• Characterization using pure shear tests, multiangle peel tests, and finite element analysis (FEA).

Main Results:

• Gradient-softening films achieved a fracture toughness of 1253.5 J/m², significantly higher than uniform films.
• Demonstrated superior peel resistance (2.1-3.6 times higher than uniform films) through 'stiff-soft synergy'.
• Films showed stability after 6-day storage and 1000 bending cycles.

Conclusions:

• The gradient-softening strategy effectively enhances both structural integrity and interfacial peel resistance in hydrogel films.
• This approach offers a novel solution for developing durable and high-performance flexible electronics.
• Potential integration with advanced manufacturing for biomimetic interfaces in soft robotics and wearable sensing.