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Developments of Multi-beam 3D Holographic Lithography for Volumetric Additive Manufacturing

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Abstract

Conventional additive manufacturing methods process a point, a line, or a plane of an object at a time. Their sequential processing nature greatly limits the fabrication speed of these methods. The recent paradigm of volumetric additive manufacturing (VAM) eliminates this sequential nature and creates the entire 3D structure all at once by performing photolithography with carefully crafted 3D optical exposure. As a result of its parallelization, their patterning step can be completed in seconds to tens of seconds for microscale to centimeter-scale fabrication. Thanks to its capability to perform internal layer-less patterning, VAM has been found to be extremely attractive for fabricating biological constructs, freeform optics, and functional devices with embedded active components. Within the class of VAM methods, those that do not require motion scanning are of particular interest for high-throughput fabrication in industrial settings. These motionless methods create 3D optical exposures in the material either using one 3D holographic writing beam or multiple beams with an orthographic projection of the object. In this dissertation, we study a hybrid approach of these prior motionless methods where multiple 3D holographic beams are coordinated to deliver the 3D exposure for building the object.Realization of such a concept requires knowledge from multiple domains. This interdisciplinary study discusses optical design, computational modeling, exposure optimization, and experimental validation of the proposed patterning method. The optical design analysis in this study establishes the physical limit of the holographic patterning systems and investigates the theoretical benefits of adopting a multi-beam configuration. Using this information, a dual-beam patterning system is designed and constructed for experimental verification. In order to test the performance limit of the proposed configuration, a novel optimization model is constructed to jointly optimize multiple holograms for patterning. The optimization model uses a differentiable sampling and a polynomial photoexcitation model to couple the holographic beam together for optimization. The versatility of the proposed optimization model is demonstrated through multiple examples with a variety of novel polymerization mechanisms and more than a hundred beams. Finally, this optimization method is used to generate optimal phase masks for patterning experiments on the dual-beam setup. As a proof of concept, multiple hollow cube structures are successfully patterned. For further development, technical challenges encountered in experiments and their potential solutions are discussed.

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This item is under embargo until September 27, 2025.