Composite metamaterial of hyperbolic nanoridges and gold nanoparticles for biosensing

Hyperbolic metamaterials have gained considerable attention in the field of optical biosensing due to their ability to support highly sensitive plasmonic modes. The high sensitivity of these electromagnetic modes mainly manifests as a strong response to variations in the bulk refractive index of the surrounding environment. However, its capability to detect low-concentration biochemical molecules near the surface of the metamaterial still requires further enhancement. In this work, we developed a composite metamaterial of gold nanoparticles and nanoridge hyperbolic metamaterials. The hyperbolic nanoridges are high-periodicity metamaterial arrays fabricated by combining electron beam lithography and electroplating. By exciting the high-sensitivity coupling modes formed by the bulk plasmon-polariton and localized surface plasmon resonance in this composite metamaterial, we achieved an improvement of over one order of magnitude in the detection limit for biomolecules, while maintaining the high bulk sensitivity of 23 333 nm RIU^-1. Our research not only plays a key role in advancing the field of real-time, high-precision plasmonic biosensing but also offers substantial promise for improving early disease detection and monitoring.