Functional Hydrogel Strain Sensors for Smart Electronic Devices: Strategies and Recent Progress

Hydrogel strain sensors are emerging in the preparation of various flexible electronic devices, particularly in wearable devices, electronic skin, and smart medical devices. However, with the rapid development in electronics industry, traditional hydrogel insufficient mechanical properties, limited frost resistance, and poor water retention have promoted the functional design and rational construction and become a topic of current interest for enhancing hydrogel-based strain sensors practical applications and next-generation industrialization. Therefore, it is necessary to understand the functionalization strategies and summarize the latest research progress of hydrogel strain sensors with maximum performance for smart electronic devices applications. Herein, this review presents the classification and structural characteristics of hydrogel materials and the sensing mechanisms of strain sensors. Then, we summarize the design strategies for the functionalization of hydrogels and examine the advanced hydrogel strain sensors with improved usage performance and functionality. Finally, the application scenarios and future application prospects of functionalized hydrogel-based strain sensors are discussed. This review provides a meaningful reference for the tailored design and development of multifunctional hydrogels for flexible electronics industry.