Binder Jetting 4D Printing of Functionally Graded Porous Multi-Materials for Biodegradable, Untethered and Multi-Stimuli-Responsive Soft Robots

Recent advances in functionally graded additive manufacturing (FGAM) have enabled the smooth integration of multiple functionalities into a single structure. The present development greatly enhances soft robotics by utilizing an efficient four-dimensional (4D) FGAM procedure, and intelligent stimuli-responsive mechanical functions in printed objects. Our study introduces a facile binder jetting approach for 4D printing functionally graded porous multi-materials (FGMM) which utilizes meticulously created graded multiphase feeder beds. These beds use compositionally graded cross-linking agents to form stable porous network structures within aqueous polymer particles, allowing for programmable hygroscopic deformation without requiring complex mechanical designs. Furthermore, a well-organized bed design with additional functional agents produces a multi-stimuli-responsive, untethered soft robot with precise stimulus selectivity. The biodegradability of the 4D-printed soft robot promotes sustainability, with a remarkable degradation rate of 96.6% within 72 hours. This novel 4D printing approach for FGMMs opens up new possibilities for intelligent and sustainable additive manufacturing in soft robotics.