3D-printed in-line and out-of-plane layers with stimuli-responsive intelligence

Abstract

Smart materials and structures with shape memory properties have recently gained attention due to their unique ability to remember their original shape, dimensional flexibility, structural programmability, and multi-material compatibilities. They have found applications in morphing structures, heat storage, flexible electronics, soft/micro-robotics, metamaterials, biomedical scaffolds, and space missions. Most applications of these systems require multifunctionality with high precision controls over multi-materials. However, most current manufacturing cannot process disparate materials without generating phase separation or structural instabilities. This research presents a new 3D printing process via the Multiphase Direct Ink Writing (MDIW) mechanism to produce in-line and out-of-plane microlayers. The selective deposition of polyether-thermoplastic polyurethane (TPU)/polycaprolactone (PCL) and polyester-TPU/iron oxide (Fe3O4) is investigated for thermal and magnetic dual stimuli-responsiveness. During the MDIW manufacturing, specific sublayers within each printing line for optimized domain size are produced with the stacking of the layers along the z-axis to investigate their influences on the stimuli-responsiveness. The mechanical, thermal, and thermomechanical characterizations can reveal the time-temperature-dimension relationships in different media (i.e., air and water) showing a precisely controlled actuation phenomenon and shedding light on their broad applications in defense, energy, health, and sustainability.