Computational Design of Self-Actuated Deformable Solids via Shape Memory Material

Abstract

The emerging 4D printing techniques open new horizons for fabricating self-actuated deformable objects by combing strength of 3D printing and stimuli-responsive shape memory materials. This work focuses on designing self-actuated deformable solids for 4D printing such that a solid can be programmed into a temporary shape and later recovers to its original shape after heating. To avoid a high material cost, we choose a dual-material strategy that mixes an expensive thermo-responsive shape memory polymer (SMP) material with a common elastic material, which however leads to undesired deformation at the shape programming stage. We model this shape programming process as two elastic models with different parameters linked by a median shape based on customizing a constitutive model of thermo-responsive SMPs. Taking this material modeling as a foundation, we formulate our design problem as a nonconvex optimization to find the distribution of SMP materials over the whole object as well as the median shape, and develop an efficient and parallelizable method to solve it. We show that our proposed approach is able to design self-actuated deformable objects that cannot be achieved by state of the art approaches, and demonstrate their usefulness with three example applications.

Phase field topology optimisation for 4D printing

“…The shape shifting functionality of the active components enables the self-actuating and self-assembling potentials of PACs, allowing them to fold, bend, twist, expand and contract when a stimulus is applied, and return to their original configurations after the stimulus is removed. This property has led to the fabrication of intelligent active hinges and origami-like objects [35,37], mesh structures [24,64] and self-actuated deformable solids [59] in the form of in the form of graspers and smart key-lock systems. We refer to the review article [52] and the references cited therein for more applications of 4D printing.…”

“…For active materials and active composites, [40,54] studied how to pattern thin-film layers within a multi-layer structure with the aim of generating large shape changes via spatially varying eigenstrains within the microstructures, while [50] aimed to optimise the microstructures of PACs matching various target shapes after a thermomechanical training and activation cycle. Later works incorporated nonlinear thermoelasticity [39,59], thermo-mechanical cycles of shape memory polymers [12], reversible deformations [49], as well as multi-material designs [65] within the topology optimisation framework.…”