Transient energy storage devices for implantable medical electronics

Transient energy storage devices represent an emerging class of biodegradable power systems that provide temporary energy for implantable medical electronics before safely degrading in vivo. From early transient primary batteries to contemporary rechargeable batteries integrated with wireless charging systems, these devices have evolved to enable a stable prolonged power supply. Through rational transient design and structural engineering, they achieve desirable electrochemical performance, tunable degradation rates, and mechanical compatibility with soft, irregular, and dynamic biological tissues. This work provides a critical review of state-of-the-art transient energy storage devices, including transient primary batteries, transient secondary batteries, and transient supercapacitors, with emphasis on their electrodes, electrolytes, encapsulation materials, fabrication processes, and applications. We critically analyze material selection strategies, transient design principles, and architecture design for various transient batteries and capacitors. Finally, we discuss existing challenges and outline future directions to guide the clinical translation of biodegradable power solutions for biomedical implants.