FUTURE OF 4D PRINTING IN SOFT ROBOTICS AND INTELLIGENT AUTOMATION

This review explains how 4D printing adds time as a fourth dimension to 3D-printed structures, so they can change shape in a programmed way. It focuses on how these shape changes can support autonomous actuation and adaptive behavior when exposed to environmental stimuli. The authors survey advances in 4D printing technologies and the smart materials used for actuation, including shape-memory polymers, hydrogels, liquid crystal elastomers, magneto-active composites, and multi-material systems. They compare performance, biocompatibility, and scalability using many quantitative metrics drawn from a large set of peer-reviewed publications. The review also covers application areas such as minimally invasive surgical devices, adaptive soft grippers, wearable exoskeletons, underwater autonomous vehicles, and micro-scale drug delivery. It discusses integrating machine learning, computational design, and bio-inspired principles to move toward closed-loop intelligent soft robotic systems, while noting challenges like fatigue, multi-stimulus control, scalable manufacturing, and regulatory compliance.