Webinar summary
This webinar, the third in the series Mastering CT: Advanced Techniques in Practice, begins by discussing how traditional ways of studying a material’s internal structure—cutting, polishing, and otherwise altering a sample before examining it—introduce expense, time, and possible artifacts. X-ray computed tomography avoids this by imaging intact samples nondestructively, making it possible to study materials dynamically and repeatedly under changing conditions. That capability forms the basis of so-called “4D CT,” which simply adds time as the fourth dimension to the familiar three-dimensional scan.
Ted showed that a 4D study means monitoring how a structure evolves—whether it’s a seed germinating, coffee beans roasting, or a lithium-ion battery electrode cracking during cycling—by acquiring a series of 3D CT volumes at successive times. He emphasized that while the term “4D” can sound like marketing jargon, in X-ray CT it has a concrete meaning: time-resolved 3D imaging that lets researchers observe real-time or periodic changes inside objects that cannot be seen by other means.
He contrasted ex situ and in situ methods. Ex situ experiments involve scanning a sample, removing it to apply stress, heat, or another treatment, and then scanning again. This allows use of standard mechanical or thermal equipment but risks disturbing the sample between scans. In situ studies are performed inside the CT instrument using miniature loading or heating stages that apply force or temperature during imaging. The advantage is that the sample never moves and the internal evolution can be captured live, though space, load capacity, and X-ray absorption by the fixtures become major limitations.
Examples illustrated both approaches. In ex situ mechanical work, Ted showed compression tests on meteorite rods and described how internal cracks propagated between scans. In situ testing, he inserted a compact mechanical stage directly into the CT chamber, showing force-displacement data and time-lapse images of cracking as it occurred. Temperature-controlled studies followed, from sintering 3D-printed ceramics to observing crystal growth in molten solder. He also shared less conventional 4D projects such as imaging bees building honeycombs—an ex situ case where samples were rescanned between bouts of hive activity—and live studies of batteries charging, where custom fixtures allowed simultaneous electrical cycling and scanning.
Polls during the session revealed that most participants were most interested in in-situ mechanical testing. Ted cautioned that no single approach is “better”; ex situ and in situ each solve different problems and can complement one another. For manufacturers, 4D CT can shorten design-to-production cycles and enable defect detection—porosity, cracks, or assembly flaws—without destroying parts. For researchers, it opens previously inaccessible views of how materials deform, react, or grow.
In a final demonstration, Ted described performing a spring-compression test inside Rigaku’s CT Lab HX using a Deben CT500 stage. He explained practical considerations such as sample alignment, travel limits, cabling clearance, and the need to record an initial scan before loading. After compression, the resulting images were compared and analyzed, showing how force curves relate to visible deformation. Complementary ex situ experiments by his colleague examined dough fermentation and salami heating, correlating structural changes to time and temperature.
In closing, Ted summarized that 4D CT merges three-dimensional imaging with temporal evolution to reveal how structures form, degrade, or respond to external stimuli. Success depends on thoughtful experiment design—controlling transportation and alignment for ex situ work, and stage constraints and setup for in-situ work. He and the moderators encouraged attendees to explore both avenues and suggested that future Rigaku webinars will build on this foundation to cover topics participants proposed. The tone throughout was practical, bridging academic curiosity and industrial application, showing that 4D CT is not just a research novelty but a versatile, nondestructive tool for understanding materials in motion.
