Intrinsically Soft Implantable Electronics for Long-term Biosensing Applications

Implantable biosensors play a critical role in healthcare and medical research by enabling real-time monitoring of physiological signals with high precion. Compared to non-invasive biosensors, implantable biosensors offer superior fidelity by minimizing external noise and ensuring direct contact with target tissues. However, conventional implantable biosensors, often composed of intrinsically rigid materials such as silicon and metals, suffer from mechanical mismatches with soft biological tissues, leading to inflammatory responses, fibrotic encapsulation, and long-term instability. To address these challenges, recent advances have focused on the development of intrinsically soft materials, which leverage soft and stretchable materials to achieve long-term biocompatibility and seamless tissue integreation. These materials have shown significant promise in neural interfaces, cardiac monitoring, and soft bioelectrodes for cronic sensing and stimulation. This review provides a comprehensive overview of these emerging biosensors, starting with a discussion of the limitations of conventional implantable biosensors. It then examines key intrinsically soft materials, including encapsulation matrices and stretchable conductors, and explores strategies for minimally invasive implantation, chronic fixation, and biocompatibility enhancement. Additionally, specific application cases are highlighted to demonstrate their practical utility. Finally, remaining challenges and future research opportunities are discussed to guide the next generation of intrinsically soft implantable biosensors toward clinical translation.