Monitoring moisture distribution in textile materials using grating interferometry and ptychographic X-ray imaging

Employing two recently developed X-ray imaging techniques, we investigated methods for observing moisture at different length scales in organic fibers and textiles. Using the coherent diffractive imaging technique of ptychographic tomography, structural features in a single coated wool fiber in both dry and humid conditions were observed at about 200 nm resolution. The reconstructed three-dimensional images yield quantitative information about the spatial density distribution in the fiber, showing that the fiber swells laterally by 8–9% in humid conditions. We further explore the applicability of grating interferometry, also known as Talbot imaging, for studying humidity transport in woven cotton, with a resolution on the order of 100 µm and a field of view of a few square centimeters. Grating interferometry inherently gives access to three complementary imaging modalities, namely absorption-, phase- and dark-field contrast, and we demonstrate that all of them are valuable and provide complementary information for the purpose of monitoring moisture in textiles.