Evolution of Micro-CT
to alleviate these issues. As an example, several different test specimens were created in plastic using 3D printing. A total of six cylindrical samples, with different internal supports, were formed. Each sample was then compressed continuously using a Deben load stage, while tomography data were collected on a TESCAN CoreTOM at a rate of one sample rotation every 5.8 seconds with a voxel resolution of 59 µm. Tis resulted in 210 full sample scans for each sample. Figure 3 provides an overview of three of these samples including their internal structure, 3D rendered snapshots of the sample throughout the process, and their associated load curves. Trough this experi- mental evaluation of deformation of different geometries, one can develop more precise simulations to best understand opti- mization for the specific needs of an application. As can be seen on the graph, no relaxation took place during the experi- ment due to a constant displacement. Imaging of beer foam. Everyone loves a good beer, but
what makes a beer good? One could certainly argue that the foam plays an important role, but why? In this experiment, we examine the collapse of a beer foam and compare the differ- ences between two different types of beer. In one case the foam stays intact over a long period of time while the foam dissipates quite quickly in the second case. Why is this important? Smell is an integral part of taste, and the beer head acts as a carrier for the aromatics of a beer. Te fact that a beer that goes “flat” tastes different isn’t just because there is less “fizziness,” but it’s also because the aromatics are less available, therefore changing the taste of the beer. In this experiment [8] the authors imaged two different beer types in the TESCAN DynaTOM, a unique gan- try-based system where the sample remains stationary while the x-ray source and detector rotate. Tis allows for a maxi- mum amount of flexibility when working with complex in situ samples or, as is the case with beer foam, delicate samples that may be distorted by the simple action of rotating the sample in a traditional micro-CT system. For beer 1, a Belgian strong ale, 70 rotations about the sample with 15 seconds per full 360o rotation at 160 µm voxel size were collected, resulting in a total experiment time of 17.5 minutes. For beer 2, a lager, the condi- tions were slightly different with 80 rotations about the sample, 9.4 seconds per full 360o
rotation, and 150 µm voxel size, result-
ing in a total experiment time of 12.5 minutes. Te foam from each sample was then analyzed to show the relation of the aver- age equivalent diameter (AED) of the pores and the height of the foam, resulting in some stark differences between the two beverages. In the Belgian ale, a much smaller equivalent pore diameter, resulting in a much more resilient and dense foam,
Figure 4: 3D renderings of three different time points (0, 2, and 9 minutes) of the beers used for this comparison. Clear differences are seen in the consis- tency of the foam head between the two types of beer. The lager foam has all but disappeared by 9 minutes, while the strong ale is holding up well. Modified from [8].
was observed in comparison with the lager. A main takeaway of this experiment: make sure to drink a lager beer quickly, but take some time when enjoying an expressive and flavorful Belgian strong ale! In all seriousness, this type of imaging and analysis can be transferred to several other lightweight foam applications, including the evolution of polymeric foams during production or under corrosive environments. Figure 4 provides a comparison of 3D renderings of the foam of the two differ- ent beers at several time points, while Figure 5 demonstrates
Figure 5: Segmentation and analysis of the foam pore sizes was performed across all 80 data sets. Shown are examples at 4 different time points, where the color represents the size of the pore (blue, smallest; red, largest). Modified from [8].
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www.microscopy-today.com • 2021 May
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