Vat Photopolymerization in a Hybrid Atomic Force Microscope: In situ, Nanoscale Characterization of the Printing Process

Vat photopolymerization is a powerful additive manufacturing technique that addresses many applications ranging from personalized medicine to mainstream manufacturing. Unfortunately, this printing process introduces micrometer-scale anisotropic inhomogeneities due to the resin absorptivity, diffusivity, reaction kinetics, and swelling during the requisite photoexposure. Previously, it has not been possible to characterize high-resolution mechanical heterogeneity as it develops during the printing process. By combining DLP 3D printing with atomic force microscopy in a hybrid instrument, heterogeneity of a single, in situ printed voxel is characterized. Here, we describe the instrument and demonstrate one of the three modalities for characterizing voxels during and after printing. In sensing Modality I, the mechanical properties of just-printed, resin-immersed voxels are mapped, providing the framework to study the relationships between voxel sizes, print exposure parameters, and voxel-voxel interactions. This mode also affords iterative print fidelity correction using the measured properties to optimize photopatterning. Overall, this instrument equips researchers with a tool to develop rich insight into resin development, process optimization, and fundamental printing limits.