Advances and future perspectives in hydrogel-based sensing technologies: a comprehensive review.

Hydrogels, with their high water content, biocompatibility, and responsiveness to environmental stimuli, have gained significant attention as promising materials in sensor technology. Hydrogel-based sensors are increasingly utilized in environmental monitoring, healthcare diagnostics, and wearable devices. This review highlights recent advancements in hydrogel-based sensing technologies, emphasizing the preparation and properties of conductive hydrogels. It discusses methods for enhancing conductivity and mechanical strength using conductive polymers and carbon nanofillers, as well as strategies for improving flexibility and biocompatibility through ionic conductivity. Key applications, such as human motion detection and health monitoring, are explored in detail. The review also addresses ongoing challenges, including the mechanical integrity of hydrogels, which impacts their durability and functionality in load-bearing applications. Achieving high sensitivity and specificity remains a complex task, and ensuring the long-term stability of hydrogel sensors continues to be a critical issue. Emerging research directions are examined, such as the development of "smart" hydrogels capable of responding to multiple stimuli and their integration into electronic devices for real-time physiological monitoring. Future improvements in material formulations and sensor design are expected to expand the versatility and robustness of hydrogel-based sensors, enhancing their applications in medical diagnostics, environmental monitoring, and personal healthcare. This review aims to serve as a valuable resource for researchers and engineers, encouraging the further development and practical implementation of hydrogel sensor technologies.