A Multifunctional Hydrogel‐Based Flexible Sensor for Synchronous Monitoring of Physical Activity and <scp>UV</scp> Exposure in Children

ABSTRACT As the distribution of social resources becomes increasingly uneven, the demand for children healthcare has become increasingly prominent. Due to the unique advantages of conductive hydrogels, they are excellent candidates for children healthcare wearable devices. However, their conventional preparation often involves time‐consuming processes and the usage of a toxic chemical initiator, posing an urgent challenge to fabricate multifunctional hydrogel‐based sensors via a green and efficient approach. In this work, we utilized an initiator and crosslinker‐free strategy stimulated by sunlight to fabricate the zwitterionic poly(sulfobetaine methacrylate‐ co ‐hydroxyethyl methacrylate) (P(SBMA‐ co ‐HEMA))‐based composite hydrogel incorporating polyvinylpyrrolidone (PVP), phosphotungstic acid (PTA), and boric acid. The resulting SHPPB hydrogel exhibited tissue‐like softness (Young's modulus ~10 kPa), favorable stretchability (up to 1449%), excellent resilience, reversible adhesion, outstanding antibacterial activity, and excellent biocompatibility. Moreover, benefited from the intrinsic conductivity and photochromic property of PTA, the as‐prepared hydrogel can be utilized to detect daily physical activities of children and the intensity of the suffered ultraviolet radiation in real time, offering colorimetric indication for UV protection. This work provides a facile and green route to construct multifunctional hydrogel‐based sensors with integrated sensing, antibacterial, and biocompatible properties, showing great potential for next‐generation children healthcare wearable devices.