Numerical investigation of IgG sensing through nanoscale topological-assisted metasurface for liquid biopsy

Topological photonics offers tightly confined, defect-immune optical modes ideal for biosensing, where sensitivity, spectral resolution, and fabrication tolerance must coexist. Conventional Guided-Mode Resonances (GMRs) sensors typically exhibit limited Q-factors, whereas high-Q photonic crystal cavities require complex fabrication and lack robustness. To bridge this gap, we present a refractive-index sensor based on a Jackiw-Rebbi topological resonance at the interface of two oppositely phased 2D GMR gratings. Under normal-incidence transverse-magnetic excitation, the device achieves Q > 1,600, bulk sensitivity of 97 nm/RIU, and a figure of merit (sensitivity & times; Q) of 1.7 & times; 105 across 870-970 nm. The enhanced tolerance to fabrication deviations, together with high-Q, high-amplitude resonant behavior and a fully planar, photolithography-compatible geometry, makes the proposed topological GMR platform a strong candidate for next-generation label-free biosensing implementations.