@article{Cho2024, 
author = {Soo Young Cho and Dong Hae Ho and Sae Byeok Jo and Jeong Ho Cho},
title = {Direct 4D printing of functionally graded hydrogel networks for biodegradable, untethered, and multimorphic soft robots},
year = {2024},
journal = {International Journal of Extreme Manufacturing},
volume = {6},
number = {2},
pages = {025002},
keywords = {intelligent and sustainable additive manufacturing, multi-material four-dimensional printing, untethered soft robot, multi-stimuli-responsive soft robot, biodegradable soft robotics},
url = {https://www.sciopen.com/article/10.1088/2631-7990/ad1574},
doi = {10.1088/2631-7990/ad1574},
abstract = {Recent advances in functionally graded additive manufacturing (FGAM) technology have enabled the seamless hybridization of multiple functionalities in a single structure. Soft robotics can become one of the largest beneficiaries of these advances, through the design of a facile four-dimensional (4D) FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed objects. Herein, we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials (FGMM) by introducing rationally designed graded multiphase feeder beds. Compositionally graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles, enabling programmable hygroscopic deformation without complex mechanical designs. Furthermore, a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus selectivity. The biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach, with immediate degradation rates of 96.6% within 72 h. The proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.}
}