Complex Light INside Channelled Hollow-core for FCS nanoparticle characterization

Fluorescence correlation spectroscopy (FCS) is an innovative technique for the detection and characterization of nanoscale species within their natural environment. It has successfully measured protein-protein and protein-lipid interaction dynamics, determined spectroscopic parameters of fluorophores and monitored binding constants among diffusing species. However, current FCS systems, predominantly based on confocal microscopes, have large footprint and inflexible focal observation volumes, limiting their applicability outside controlled laboratory settings. There is a strong need for compact, flexible FCS solutions. My approach addresses this need by exploiting the interaction between diffusing nanoparticles (NPs) and complex light fields within a hollow-core optical waveguide (HCW), nanoprinted directly onto an optical fiber facet. This advancement not only paves the way for a portable FCS tool suitable for clinical environments but also has the potential to enhance existing FCS technology. Our device offers two major advantages: (i) prolonged observation times due to the confinement of NP diffusion within the waveguide core, and (ii) rapid detection that surpasses image-based techniques by recording only emitted powers. By integrating extended observation periods with high acquisition rates, my FCS system facilitates the study of fast dynamic processes and interactions at the single NP level, addressing fundamental questions in life sciences, material science and light-matter interactions in general. Furthermore, my opto-fluidic platform supports both fluorescence and scattered light detection, enabling the investigation of NPs that cannot be fluorescently labeled. Notably, it allows for simultaneous measurement of fluorescence and scattered light, unlocking new pathways for exploring NP processes, such as fluorescence quenching.