# Voxel Design of Grayscale DLP 3D‐Printed Soft Robots

## TL;DR

This paper introduces a new design framework for grayscale DLP 3D printing to create soft robots with tunable material properties and complex motions.

## Contribution

A novel design framework combining grayscale-dependent material models and voxel-based simulations for grayscale DLP 3D printing.

## Key findings

- A grayscale-dependent hyperelastic model links grayscale values to mechanical properties.
- A voxel-based finite-element model enables efficient mechanical performance calculations.
- The framework reduces stress concentration and enables programmable multimodal robot motions.

## Abstract

Grayscale digital light processing (DLP) printing is a simple yet effective way to realize the variation of material properties by tuning the grayscale value. However, there is a lack of available design methods for grayscale DLP 3D‐printed structures due to the complexities arising from the voxel‐level grayscale distribution, nonlinear material properties, and intricate structures. Inspired by the dexterous motions of natural organisms, a design and fabrication framework for grayscale DLP‐printed soft robots is developed by combining a grayscale‐dependent hyperelastic constitutive model and a voxel‐based finite‐element model. The constitutive model establishes the relationship between the projected grayscale value and the nonlinear mechanical properties, while the voxel‐based finite‐element model enables fast and efficient calculation of the mechanical performances with arbitrarily distributed material properties. A multiphysics modeling and experimental method is developed to validate the homogenization assumption of the degree of conversion (DoC) variation in a single voxel. The design framework is used to design structures with reduced stress concentration and programmable multimodal motions. This work paves the way for integrated design and fabrication of functional structures using grayscale DLP 3D printing.

A design and fabrication framework for grayscale DLP printing is developed by combining a grayscale‐dependent hyperelastic constitutive model and a voxel‐based finite‐element model. A multiphysics modeling and experimental method is developed to validate the homogenization assumption of the degree of conversion variation of a single voxel. The framework is used in reducing stress concentration and multimodal soft robots.