Dye diffusion in fibers: 3D reconstruction of trilobal nylon fiber dyed with fluorescein studied with laser confocal microscopy

We study of dye diffusion in fibers using confocal microscopy, where the diffusion coefficient of the dye is determined by imaging the fluorescence intensity profile across the fiber cross-section as a function of time. LSCM-FRAP (Laser Scanning Confocal Microscopy-Florescence Recovery After Photo-bleaching) is a non-invasive technique based on irreversibly bleaching a fluorescent probe in a well defined volume element with a high intensity laser. Since LSCM employs spot illumination and strongly eliminates out of the focus light, the internal structure of the fiber can be visualized without physical sectioning of the fiber. This research is motivated both by desire to better understand diffusion of dyes into fibers and by desire to provide solution to the problem of dye streaking in fabrics observed in industry.