Roll-to-roll tomographic volumetric additive manufacturing for continuous production of microstructures on long flexible substrates

Abstract

Tomographic volumetric additive manufacturing (VAM) has proven viable to 3D print diverse materials including polymer, glass, ceramic, and hydrogel at the centimeter scale. As tomographic VAM is scaled to the microscale many of its advantages are translatable including smooth layer-less surfaces, support-free and shear force-free printing, material flexibility, and speed of production. However, according to geometric optics, the depth of field is inversely proportional to the square of the numerical aperture which must be increased when the image projection optical system is redesigned for microscale tomographic VAM. Consequently, the build volume is substantially reduced. Additionally, microscale tomographic VAM is currently limited to batch production, i.e., the photoresist container must be exchanged after the exposure phase is completed. In this work, we introduce roll-to-roll (R2R) tomographic VAM in which these limitations are addressed by “unwrapping” the precursor material into a film enabling continuous production of microstructures with theoretically unlimited length. We elaborate the design of a projection optical system which enables this configuration via focus tuning synchronized with the refresh cycle of a digital micromirror device. We describe the process of iteratively optimizing and segmenting sinograms to produce long aperiodic microstructures with the focus tunable optical system. Furthermore, we formulate a thermally reversible organogel photoresist which is deposited onto the substrate in films multiple millimeters in thickness with slot-die coating. Finally, we will present progress on printing with the R2R tomographic VAM system.