Three-dimensional printed ionic conductive hydrogels with tunable mechanical properties for wearable strain sensors

Area of Science:

• Materials Science
• Biomedical Engineering
• Polymer Chemistry

Background:

• Flexible sensors are crucial for wearable devices but face challenges in mechanical properties, sensing performance, and strain range.
• Developing hydrogels with enhanced mechanical strength and broad applicability is an ongoing research area.

Purpose of the Study:

• To optimize hydrogel printing for high-fidelity fabrication of flexible sensors.
• To enhance the mechanical properties and sensing capabilities of ion-conducting hydrogels through a dual-ion synergistic strategy.

Main Methods:

• Optimized process parameters for N-(2-Amino-2-oxoethyl) acrylamide/carboxymethyl chitosan/methyl cellulose hydrogel printing.
• Introduced Fe³⁺ and Li⁺ ions via solution immersion to create a "stiff-tough-ductile" balanced network.
• Fabricated and tested 3D-printed reticulated hydrogels for mechanical and sensing performance.

Main Results:

• Dual-ion treated hydrogels demonstrated enhanced mechanical properties: modulus of elasticity (266 kPa), toughness (1245 kJ/m³), and elongation at break (437%).
• Achieved high sensitivity (strain factor of 2.57) and a broad detection range (0-300%) with excellent fatigue durability (>100 cycles at 60% strain).
• Demonstrated remarkable resistance to swelling.

Conclusions:

• The dual-ion enhancement strategy significantly improves hydrogel mechanical properties and sensing performance for flexible sensors.
• The developed hydrogels are suitable for high-precision detection of human body movements, advancing wearable electronics.
• This work provides new insights for designing and developing advanced flexible sensors and conductive hydrogels.