Multifunctional Bioelectronics Achieved by Empowering Hydrogels with Phase‐Transition Ability

Abstract Flexible electronics are of great interest in wearable bioelectronics, biomedicine, and robotics, with hydrogel emerging as an ideal candidate due to its excellent biocompatibility, stretchability, and flexibility, making it suitable for applications in wearable electronics, clinical medicine, and soft robotics. However, traditional hydrogels are limited by restricted application scenarios, poor controllability, and insufficient smart responsiveness. In contrast, phase transition hydrogels, characterized by their reversible phase transition properties and multifunctional adaptability, represent a promising advancement in flexible electronics. This review systematically examines the various reaction types of phase transition hydrogels, detailing their underlying reaction mechanisms and the materials involved. Furthermore, the principles and applications of phase transition hydrogels in wearable electronics, clinical medicine, and optical devices are analyzed. Additionally, their roles in thermal management devices and soft robotics are explored. Finally, the prospects and challenges of phase transition hydrogel‐based flexible electronics are discussed, emphasizing the need for further optimization of molecular structure and cross‐linking system design, precise tuning of phase transition temperature and transition rate, enhancement of long‐term stability, and seamless integration with conventional silicon‐based electronics.