Micro- and Nano-Sensors at Exceptional Points

Sensing lies at the heart of modern physics and engineering. Particularly in some extreme scenarios, sensing systems are pushed toward their ultimate performance limits, demanding not only advances in materials and micro-/nano-fabrication but also continual innovation in device architecture. Yet, compared with material and structural optimization, the sensing principle itself has long received less attention. Exemplified by Fabry-Pérot cavities, they generally exhibit a linear response to external perturbations, fundamentally constraining resolution in the weak-perturbation regime. This limitation has motivated a shift from conventional Hermitian systems to non-Hermitian platforms, most notably those operating at exceptional points (EPs), where perturbation-induced spectral response follows a $N^{\mathrm{th}}$ -root dependence (with $N$ the EP order) and can therefore offer remarkably enhanced sensitivity. Over the past decade, this concept has evolved from a subject of wave physics into a rapidly growing direction in enhanced sensing. Following this, we herein aim to provide a comprehensive overview of EP-based sensing systems, covering the theoretical fundamentals, representative realizations, and recent advances in practical implementations. Beyond summarizing recent progress, this review seeks to highlight how non-Hermitian physics can open new directions for the wider sensing community, from theoretical fundamentals to real-world microsystem technologies.