Biomolecular Sensing at the Interface between Chiral Metasurfaces and Hyperbolic Metamaterials.

In recent times, biomolecular sensing to recognize genetic fragments and proteins is spurring unprecedented interest as a diagnostic protocol for cancer and infectious diseases. Significant efforts have been made to design nanomaterials able to control the light-matter interaction at the single nanometer scale, where genes and proteins bind specifically to receptors. Here, we numerically show how the interface between a chiral metasurface and hyperbolic metamaterials can enable both high sensitivity and specificity for low-molecular-weight nucleic acids and proteins. As we have recently reported, hyperbolic dispersion metamaterials allow molecular biorecognition with extreme sensitivity because of coupled and highly confined plasmon polaritons. Specificity is almost exclusively achieved by receptor-ligand interaction at the in-plane sensing surface. Interestingly, an adapted out-of-plane chiral metasurface enables three key functionalities of the hyperbolic metamaterial sensor. Computational effort reveals that helicoidal metasurfaces can act as (i) efficient diffractive elements to excite surface and bulk plasmon polaritons; (ii) out-of-plane sensing branches to reduce the diffusion limit and increase the sensing surface; and (iii) biorecognition assay also via circular dichroism and chiral selectivity.