Monitoring the silk fabrics at different process stages by using FLIM

Mulberry silk fabrics are very popular due to their soft lustre, comfortable handle and smooth texture. Currently, the traditional textile testing methods are deficient to provide a fast and sensitive directional detection way or quantitative characterization data to study different process stages of the textile. Here, we used crepe de chine as silk samples for microscopy detection. Both confocal fluorescence microscopy and fluorescence lifetime imaging microscopy (FLIM) methods have been applied into observing samples at different process stages to obtain their surface morphology and fluorescence lifetime distribution. The confocal results showed that the samples had autofluorescence under excitation at several wavelengths. The fluorescent intensities of different samples from a series of process stages of the silk manufacture or the air-dried pure sericin were obtained under the 640 nm excitation, which was used in the following FLIM experiments. FLIM results showed that in undyed group, the lifetime values of the raw silk fabric were around 2400 ps. The lifetime of the sample with partial sericin left were similar to those in the raw silk fabric while the intensities were decreased. The optical properties of the dyed fabrics were similar to the undyed group, but their lifetime values were lower than those of the undyed group, suggesting that the silk fabrics had different optical properties due to the factors including the residual amount of sericin and dyeing condition. Briefly, FLIM can provide a non-destructive method for real-time quantitative investigation of the silk fabrics at different process stages, providing information for parameters such as the residual amount of sericin.