Tubular SiO2−TiO2 Hybrid Inverse Opal Porous Layers as an Optical Interferometric Platform

Abstract Inspired by the efficient mass transfer properties of biological vascular systems, tubular structures have garnered significant attention in sensing due to their outstanding hydrodynamic performance. Transforming these passive conduits into active sensing platforms requires the in-situ integration of high-performance signal transduction platforms. This work reports an optical interferometry platform based on a tubular SiO2−TiO2 hybrid inverse opal (IO) structure for label-free, real-time biosensing. By employing a sol−gel co-growth, the hybrid IO films are synthesized directly on tube inner walls, combining silica’s robustness with titania’s high refractive index to ensure stable, high-fidelity Fabry−Pérot signals. Through the experiment of refractive index corresponding to salt concentration gradient demonstrates that the high porosity (74%) of the IO structure effectively eliminates steric hindrance for macromolecular diffusion, achieving a six-fold increase in optical sensitivity compared to traditional silica colloidal crystal structures. At the hydrodynamic level, the macroscopic tubular configuration promotes convective transport, ensuring rapid response kinetics even under high flow rates. Furthermore, by functionalizing the luminal wall, the platform enables the specific quantitative detection of IgG in diluted whole blood. This optical interferometry platform, which integrates periodic porous structures with biomimetic fluidic interfaces, offers a pathway for developing next-generation biosensing.