Highly Sensitive Zwitterionic Hydrogel for Dual-Mode Temperature Sensing with Zinc Ion Regulation

Abstract

Thermoresponsive hydrogels with an adjustable response range, high sensing sensitivity, and the capability of temperature sensing without a power supply are of great significance for their portable application scenarios. In this work, a zwitterionic hydrogel with dual optical–electronic thermoresponsive behavior was developed via a facile one-pot strategy through the copolymerization of SBMA and AA in the presence of Zn2+, with PLL as a macromolecular cross-linker. By virtue of diverse dynamic reversible interactions within the hydrogel network, its optical transition temperature can be precisely tuned over an exceptionally broad range from 6.6 to 52 °C by regulating the SBMA/AA mass ratio and Zn2+ concentration. Benefiting from the introduction of Zn2+ and the unique zwitterionic network structure, the hydrogel exhibits excellent ionic conductivity and an ultrahigh TCR of –7.78%·°C–1 within the physiological temperature range (35–38 °C). Meanwhile, a synchronized visual transparency transition enables dual-mode optical–electronic temperature sensing. Furthermore, the hydrogel shows autonomous self-healing at room temperature and robust adhesion to various substrates, ensuring stable interfacial contact for sensing applications. This work provides a versatile design strategy for highly sensitive dual-mode temperature sensing hydrogels regulated by zinc ions, demonstrating great potential in flexible temperature monitoring and visual wearable healthcare electronics.