Although most people associate x-rays with medical applications or security scans, their use is widespread, with many industrial sectors and scientific disciplines dependent on them. For over a century, x-rays have been primarily used in a binary fashion, recording if they are absorbed by matter or not, termed attenuation contrast. However, x-rays are waves, exhibiting a much more complex range of interactions with matter. One subtle interaction is the tiny change in speed x-rays experience travelling in different materials, producing a “phase” contrast orders of magnitude more sensitive than attenuation contrast. Similarly, x-rays undergo microscopic changes in direction as they travel through heterogeneous materials, termed “dark field” contrast. Using phase and dark field contrast offers to transform x-rays use, enabling detection of features previously considered “x-ray transparent” while revealing internal microscopic structures of objects previously unseen.
Our binary use of x-rays has not only limited the spatial and chemical resolution we obtain, but due to poor attenuation contrast, each image requires significant time. Using x-ray’s wave properties will enable dynamic and multi-modal imaging, obtaining three channels of information, enabling much more sensitive and specific sample analysis. We will achieve this by coupling an attenuation channel with a phase contrast channel that reveals x-ray transparent features and a dark field channel that exposes an objects internal microscopic structure. This will reveal for the first time microstructural and phase evolution with micron resolution over a large field of view.
Once developed, we will apply this innovative tool to study one of the under-pinning technologies of the Digital Manufacturing revolution–laser additive manufacturing (LAM). LAM enables the 3D printing of metal components with previously unrealised structural complexity. LAM has the potential to be the new standard in manufacturing but defect formation due to our lack of knowledge of the internal physics leads to non-optimal final properties. Our new dynamic, multi-modal imaging will enable the first studies of LAM microstructures forming in milli-seconds with micron resolution in realistic build structures.
Finally, the mechanism by which we will make our system sensitive to phase and dark field has the additional advantage to provide enhanced – and tuneable – spatial resolution. This will make it possible to see the internal features of an object at a coarser resolution, identify areas of particular interest (for example through the dark field channel, sensible to microstructural variations), and then zoom in to fully resolve them in the video – therefore adding a powerful dimension to our inspection tool. Once validated on additive manufacturing, we expect the technology to find uses in many other areas including medical imaging, biomedical studies and materials science.