X-ray computed tomography (XCT) imaging is a non-destructive method that can reveal object's internal details in three dimensions (3D) with a high basic spatial resolution down to 500 nm. Typical sample sizes for low-density materials like polymers range from centimeters to a few hundred micrometers.

With state of the art XCT devices, even composite materials with very similar densities can be imaged. An example is a resin containing self-healing polymer - ploy (ethylene-co-methacrylic acid) (EMAA). Self-healing agents can potentially restore mechanical properties and extend the service life of composite materials. Thermoplastic healing agents have been extensively investigated in epoxy matrix composites for this purpose due to their strong adhesion to epoxy and ability to fill in microcracks. Specimens with various contents of thermoplastic and different particle sizes were manufactured and the influence of particle content and size was analyzed.

Two-photon polymerization (2PP) is a 3D printing method to fabricate extremely small structures. The 3D printed pyramids studied here have a side length of 141 µm and a height of 100 µm. Detection of internal (hidden) voxel-sized structures is possible to visualize with XCT, the size and shape of such deformations can be quantified. XCT is able to determine the origin of different flaws in our fabrication procedure, displays them, and finds an individual solution for the missing tip and the misinterpreted lines in our slicing code. Therefore, XCT is a highly useful tool for the process feedback of Direct Laser Writing (DLW) produced structures on the micro- and nano-meter.