A novel technique based on Bloch surface waves sustained by one-dimensional photonic crystals to probe mass transport in a microfluidic channel

We report on the use of an optical sensing platform based on Bloch surface waves sustained by one-dimensional photonic crystals as a novel optical tool to probe in real time the fluid flow at a boundary wall of a microfluidic channel under dynamic conditions. Understanding how fluid flow interacts with wall surfaces is crucial for a broad range of biological processes and engineering applications, such as surface wave biosensing. The proposed platform provides nanometric resolution with respect to the distance from the boundary wall sensor's surface. Here, for the first time, we report on the experimental investigation on the temporal evolution of the interface between two fluids with different refractive indices under convective and diffusive conditions. The temporal evolution of the fluids interface in proximity of the wall is recovered. From the data analysis, the diffusion coefficients of glucose and glycerol in water are measured and found in good agreement with the literature. Tuning the one-dimensional photonic crystals geometry and the Bloch surface wave's dispersion has the potential to probe the fluid flow in an extremely wide range of distances from the microfluidic channel wall.