Metasurfaces for biomedical applications: materials design, optical engineering, and system integration

Metasurfaces, planar optical elements composed of subwavelength nanostructures, are catalyzing a paradigm shift in biomedical imaging and diagnostics through their unprecedented ability to control light at the nanoscale. This review provides a materials-centric analysis of the critical progression in metasurface design: from foundational all-metal plasmonic systems to all-dielectric platforms, and ultimately, their integration with CMOS technology for biomedical applications. We first examine all-metal metasurfaces, which leverage intense localized surface plasmon resonances (LSPRs) for field-enhanced spectroscopy but are fundamentally constrained by intrinsic Ohmic losses that limit resonance quality factors (Q-factors) and sensing resolution. Hybrid metal-dielectric architectures are then analyzed as a strategy to mitigate these losses while retaining strong field enhancement. A significant performance leap is realized with all-dielectric metasurfaces, where low-loss materials support high-Q Mie resonances and quasi-bound states in the continuum (quasi-BIC), enabling unprecedented sensitivity. This advancement facilitates record-breaking detection limits in label-free biosensing and single-molecule fluorescence analysis. Beyond biosensing, we demonstrate how wavefront engineering principles address long-standing limitations in biomedical imaging, enabling miniaturized, high-performance systems for optical coherence tomography (OCT), multi-contrast microscopy, and endoscopy. Finally, the review addresses the crucial challenge of clinical translation by exploring system-level integration with CMOS technology and culminating in a vision of AI-enabled sensing platforms that promise to transform point-of-care diagnostics and fundamental biological discovery.