Biomimetic hierarchical structure for high-performance implantable fiber sensors

Implantable fiber sensors are emerging as viable platforms for continuous in situ monitoring of physiological signals, yet their clinical translation remains limited. The core challenge lies not only in balancing mechanical compliance, electrical reliability, analytical specificity, and long-term stability but also in maintaining these properties at the tissue-device interface throughout chronic implantation. Biomimetic hierarchical architectures, which are common in living systems, have provided a practical route by enabling structural and functional integration across multiple scales. In this review, we summarize recent progress in biomimetic design principles for improving the performance of implantable fiber sensors. We first discuss bioinspired hierarchically structured conductive fiber substrates that combine conductivity, flexibility, and resistance to cyclic deformation. We then focus on bioinspired interfaces, membranes, and surface coatings to improve sensitivity, regulate mass transport, and suppress biofouling. Finally, we address mechanically adaptive and self-stabilizing interphases and discuss biosafety, biocompatibility evaluation, and postprocessing compatibility for the clinical translation of these sensing systems. Overall, this review aims to provide actionable biomimetic design insights that can accelerate the development of next-generation implantable fiber sensors with improved long-term performance and clinical applicability.