CaCl2-Enhanced Interpenetrating Polymer Network Hydrogels with Stable Freeze Resistance and Sensing Durability...

Area of Science:

• Materials Science
• Polymer Chemistry
• Wearable Electronics

Background:

• Hydrogels are limited at subzero temperatures due to ice crystallization, dehydration, and mechanical embrittlement.
• This restricts their use in flexible electronics and wearable sensors operating in cold environments.

Purpose of the Study:

• To develop an anti-freezing hydrogel with excellent mechanical, adhesive, and strain-sensing properties for low-temperature applications.
• To investigate the role of calcium chloride (CaCl2) in enhancing hydrogel performance at subzero temperatures.

Main Methods:

• Fabrication of a double-network (DN) hydrogel combining covalently crosslinked P(NIPAm-co-HEA) and ionically coordinated poly(acrylic acid) networks.
• Incorporation of CaCl2 to regulate water states and suppress ice formation.
• Characterization of mechanical properties, ionic conductivity, adhesion, and strain-sensing capabilities at subzero temperatures.

Main Results:

• The optimized BNP-6 hydrogel exhibited remarkable low-temperature performance, with a tensile strength of 0.16 MPa and elongation at break of ~849% at -30 °C.
• The hydrogel maintained high ionic conductivity (44.1 mS cm-1 at -10 °C) with minimal decrease and stable properties over freeze-thaw cycles.
• Demonstrated reliable strain-sensing, adhesion, and self-healing under subzero conditions.

Conclusions:

• CaCl2-enhanced DN hydrogels offer robust anti-freezing, mechanical, and sensing properties for low-temperature applications.
• These hydrogels show significant potential for wearable electronics and bioelectronic interfaces operating in harsh, cold environments.