Self-illuminated plasmonic biosensor enabled by inelastic tunneling luminescence

Plasmonic nanostructures enable strong electromagnetic field enhancement and subwavelength light confinement, making them highly attractive for optical biosensing. However, conventional surface plasmon resonance sensors rely on external light sources and bulky optical components, limiting their portability and on-chip integration. Here, we present a self-illuminating plasmonic biosensor that operates without any external optical excitation. The device integrates a metal–insulator–metal tunnel junction with a plasmonic metasurface, enabling intrinsic light generation via inelastic electron tunneling. The generated photons couple efficiently to plasmonic lattice modes, providing high sensitivity to refractive index changes at the sensor surface. The gold metasurface simultaneously serves as an electrical contact and a plasmonic resonator, allowing direct electrical-to-optical transduction. The device exhibits uniform emission over a large area under low bias and supports well-defined plasmonic modes that govern the emission spectrum. Biosensing performance is demonstrated using polymer films and biofilms, achieving detection sensitivity comparable to state-of-the-art passive plasmonic sensors. This compact, label-free platform offers strong potential for integration into next-generation biosensing and diagnostic systems.