2.7. Synchrotron Computed Microtomography (μ-CT)

Synchrotron X-ray tomographic microscopy was performed at the TOMCAT beam-line X02DA of the Swiss Light Source, Paul Scherrer Institute (Villigen, Switzerland). The dried sponge samples were cut into cylinders of 5 mm in diameter using a plastic straw, attached to a sample holder with wax and investigated in a dry state, as well as after addition of decane or water. Decane was mixed with 10 wt% 1,10-diiododecane (Sigma Aldrich, St. Louis, MO, USA) for enhanced contrast. A total of 1500 projections were acquired over 180° at an X-ray energy of 12 keV and an exposure time of 250 or 120 ms with a pco.Edge 5.5 camera (pco, Kelheim, Germany). Utilization of a 10x optical magnification of the X-ray image produced on the 20 μm thick LuAG:Ce scintillator resulted in an effective pixel size of 0.65 µm and a view field of 1.4 × 1.7 mm². Reconstruction of the tomographic volume data sets was performed with gridrec [31] using a propagation-based phase contrast algorithm [32] to enhance the contrast between the solid material, air and liquid phase. Binarization and contrast enhancement were performed using Avizo (ThermoFischer Scientific, Waltham, MA, USA) and ImageJ [33].