Dual-Mode Electrical-Optical Nanocomposite Hydrogel with Enhanced Upconversion Luminescence for Strain and pH Sensing

Area of Science:

• Materials Science
• Nanotechnology
• Biomaterials

Background:

• Developing advanced materials for simultaneous sensing is crucial for next-generation electronics.
• Hydrogels offer biocompatibility and flexibility, but often lack multi-modal sensing capabilities.

Purpose of the Study:

• To create a dual-mode electrical-optical nanocomposite hydrogel.
• To integrate upconversion nanoparticles and quaternized chitosan into a polyacrylamide network for enhanced sensing.

Main Methods:

• Synthesized a hybrid hydrogel using carboxyl-modified upconversion nanoparticles (UCNPs-COOH) and quaternized chitosan (CQAS) within a polyacrylamide (PAAm) network.
• Characterized the hydrogel's optical transparency, mechanical properties, adhesion, and luminescence.
• Evaluated its performance as a resistive strain sensor and an optical pH sensor.

Main Results:

• The hydrogel demonstrated high optical transparency (>90%), excellent mechanical properties (1742% fracture strain), and robust adhesion.
• It functioned as a sensitive resistive strain sensor (gauge factor up to 13.85) and a ratiometric optical pH sensor (pH 1-13) with excellent stability.
• CQAS improved UCNP dispersion and luminescence intensity, evidenced by a prolonged fluorescence lifetime.

Conclusions:

• The developed dual-mode hydrogel offers a reliable platform for simultaneous mechanical and chemical monitoring.
• Its unique properties hold significant promise for applications in wearable electronics, smart healthcare, and environmental sensing.