Cellulose nanocrystalline hydrogel based on a choline chloride deep eutectic solvent as wearable strain sensor for...

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Choline chloride-based deep eutectic solvents (DES) show promise for wearable strain sensors due to viscoelasticity, biocompatibility, and strain sensitivity.
• Traditional hydrogels lack the necessary conductivity and mechanical robustness for effective wearable strain sensor applications.

Purpose of the Study:

• To develop novel ionic inorganic/organic interpenetrating (IPN) hydrogels with improved properties for wearable strain sensing.
• To investigate the potential of polyvinyl alcohol (PVA) as a hydrogel matrix in DES for the first time.

Main Methods:

• Preparation of IPN hydrogels using a cyclic freezing/thawing method.
• Incorporation of cellulose nanocrystals (CNCs) and graphitic carbon nitride nanosheets (g-C3N4) into a DES/PVA hydrogel matrix.
• Characterization of mechanical properties, thermal diffusivity, and electrical conductivity.

Main Results:

• The developed DES/PVA/CNCs/g-C3N4 hydrogel exhibited excellent mechanical properties, including high tensile strength (≈ 2.55 MPa) and elongation (≈1200%).
• Enhanced thermal diffusivity (up to 0.675 W/mK) and conductivity (up to 0.18 mm²/s) were achieved through the addition of CNCs and g-C3N4.
• The hydrogels demonstrated accurate in-situ detection of human motion across various joints (fingers, wrists, elbows, knees).

Conclusions:

• The synergistic interactions from hydrogen bonding among DES, CNCs, g-C3N4, and PVA chains contribute to the enhanced properties.
• These flexible, self-recovering hydrogel strain sensors with good thermal and electrical conductivity have significant potential in intelligent robotics, bionic prostheses, and human care.
• The study successfully developed a new class of hydrogel materials for advanced wearable sensing applications.