Towards multiscale X-ray tomographic imaging in membrane science - A perspective

Tomographic X-ray imaging techniques offer novel opportunities for studying membranes and membrane processes in 3D on a spatial resolution not seen before. Traditional 2D imaging techniques used to characterise membranes have limitations that can be overcome by tomographic X-ray imaging. Tomographic X-ray imaging can provide information in 2D/3D or 4D (3D plus time) on membranes, membrane modules, and membrane processes on a scale ranging from micro-to nanometre. They offer the possibility to uncover many fundamental issues related to membrane science, including the detection and monitoring of macroscopic biofilm forma-tion, scaling, and cake build-up. High-resolution nanotomographic X-ray imaging enables even microscopic characterisations such as pore size distribution or pore network analysis. This Perspective paper introduces the tomographic X-ray imaging techniques with the most potential for membrane science: microtomography, nanotomography, holotomography, and ptychotomography, and presents their applications in the literature regarding the field of membrane science. Based on these findings and our experiences opportunities, challenges, and limitations of tomographic X-ray imaging techniques are discussed. It is concluded that in the near future tomographic X-ray imaging techniques will become increasingly common analytical techniques for membrane manufacturers, scientists, and users.