3D visualisation of cellulose structures across length scales in hardwoods by multimodal X-ray imaging

Hierarchical soft materials, such as wood and wood-based materials, possess complex structures extending from nano- to millimetre scales that critically influence their mechanical and chemical performance. Comprehensive multiscale characterisation is therefore essential for advancing the research and development of sustainable, bio-based materials. In this study, we demonstrate a three-dimensional multimodal X-ray imaging method of hierarchical structures by combining small- and wide-angle X-ray scattering computed tomography (SWAXS-CT) with high-resolution X-ray microtomography (μCT) in a single experiment, using wood as a representative example. SWAXS-CT enables the spatial mapping of nanoscale properties, e.g., crystallite size and orientation parameters of cellulose microfibrils, while μCT provides complementary information on microscale cellular structures. Spatial correlation of nanoscale structural parameters with cellular anatomy in birch and aspen samples facilitates the identification of differences in cellulose distribution, chain orientation, and microfibril structure across tissue types such as xylem, phloem, and tension wood. Additionally, we assess radiation dose implications and resolution trade-offs inherent to the combined experiments. This work underscores the effectiveness of complementary synchrotron X-ray imaging modalities for resolving the structure–property relationships in hierarchical lignocellulosic materials. Graphical Abstract Schematic illustrating the value of combining complementary techniques in the investigation of hierarchical materials such as wood. Full-field microtomographic imaging enables the visualisation of cellular structures at centimetre to micrometre length scales, while SAXS and WAXS provide access to nanoscale and atomistic features of the cellulose microfibrils, i.e., the smallest structural components within the tissues