Empowering Human-Machine Interfaces: Self-Powered Hydrogel Sensors for Flexible and Intelligent Systems

Conventional rigid human-machine interfaces (HMIs) face significant limitations, including mechanical mismatch with human skin and dependence on batteries requiring frequent replacement/recharging, hindering seamless and biocompatible interactions. Self-powered hydrogel sensors, characterized by properties such as energy autonomy, tunable mechanics, tissue-like softness, and biocompatibility, have emerged as promising candidates for advancing wearable healthcare, soft robotics, and next-generation HMIs. However, challenges encompassing long-term cycle stability, complete energy autonomy, and adaptive smartness need to be addressed for their further development. Therefore, a systematic understanding of the development and current challenges of self-powered hydrogel sensors as HMIs is of great importance for realizing their full potential in flexible and intelligent interaction paradigms. This paper reviews the development of self-powered hydrogel HMIs, focusing on performance-optimizing strategies for diverse requirements, categorization by energy generation mechanisms, key applications with emphasis on artificial intelligence (AI)-enabled smartness, and their limitations. Finally, the challenges and future opportunities associated with self-powered hydrogel HMIs are discussed. This review is believed to provide guidelines for advancing next-generation HMIs that bridge energy autonomy, multimodal sensing, and AI-enhanced responsiveness, with hydrogel sensors serving as a cornerstone.