As magnetic resonance techniques continue to be adapted for a wide range of industrial, agricultural, and medical applications, the development of custom reference objects that ensure properly functioning equipment and processing techniques is necessary. Some reference objects, especially those designed for magnetic resonance imaging (MRI), are intended to mimic systems with fine structures, such as the roots of a plant or blood vessels, and require intricate designs. Stereolithography (SLA) 3D printing is a valuable tool in which liquid resin is cured using a laser and allows for the design of specially customized structures. Since the 3D printed structure is MRI invisible, voids or channels in the structure must be filled with liquids that give MRI signals in order to produce an image. However, printing objects that contain small features, such as thin channels, can be difficult to fill with liquid as excess resin can remain in the channels causing blockages if left to cure. One method to overcome this is to fuse together two pieces, which have the fine details exposed on the surface, so that excess resin can be removed from the small spaces before the final cure.
The work presented here uses single-sided nuclear magnetic resonance (NMR) to investigate the curing process of 3D printing compatible resins. As the resin cures, both the measured T2 relaxation rate and the magnitude of the spin echo decay. Differences between the NMR measurements of cured and uncured resin can be used to determine if there is unwanted, uncured resin remaining in small channels or crevices of the printed object. Removal of uncured resin will aid in the production of more accurate and intricate MRI reference objects. Furthermore, the NMR measurements can be used to determine if two or more pieces are adequately fused together and fully cured.