Multiphysics Material Screening for Microwave Volumetric Additive Manufacturing

Volumetric Additive Manufacturing (VAM) shows a great deal of promise for rapidly printing complex objects with no support material. However, conventional VAM techniques require an optically transparent feedstock. To surpass this limitation, we have been developing a microwave VAM (MVAM) system which uses focused and/or shaped microwave radiation to locally and controllably cure materials inaccessible to conventional VAM. Specifically, we have been concentrating on highly-loaded (~50% v/v) ceramic/binder mixtures which can be sintered into fully-dense ceramic parts following an initial MVAM step. The development of material formulations for this new MVAM paradigm requires us to consider numerous coupled phenomena – microwave heating, thermal diffusion, and curing kinetics – which all can affect process variables such as resolution and time-to-cure. Here, we use fully-coupled multiphysics modeling to screen the full material parameter space and identify ideal formulations for MVAM processing. These simulations are informed by thermal, chemical, and dielectric characterization of representative MVAM feedstock material. We also investigate the role that additives can play in further optimizing the thermal and chemical response of MVAM feedstock. Finally, we perform controlled microwave curing experiments in a waveguide to test and validate our model. This work is instrumental to the rational design of materials for rapid, high-resolution MVAM processes.<br/><br/>This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.