Modeling and design of grayscale DLP printed voxel soft structures by hyperelastic Mooney-Rivlin constitutive model
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Grayscale digital light processing (DLP) printing is a technique that can achieve variations in material properties by adjusting grayscale values, but designing grayscale DLP 3D printed structures is challenging due to the complexity of structures, nonlinear material properties, and voxel-level grayscale distribution. In this work, we present a design and fabrication framework for grayscale DLP printed soft structures by combining a grayscale-dependent hyperelastic constitutive model and a voxel-based finite element model. A grayscale-dependent hyperelastic Mooney-Rivlin constitutive model is proposed to characterize the nonlinear behavior of the materials with varying grayscale values. Voxel-based finite element model enables efficient calculation of mechanical performances with different material properties. We use a hybrid resin that enables high stretchability (> 60%) and strong recovery of the printed structures. The design framework facilitates the design of structures with desirable features such as reduced stress concentration, desired stress-strain curves, negative Poisson’s ratios, and programmable multimodal motions. The work introduces an innovative approach to designing and fabricating functional structures using grayscale DLP 3D printing.