4D printing: From emergence to innovation over 3D printing

4D printing aims to incorporate a product’s blueprint into a flexible, intelligent material using a standard 3D printer. It can be assembled or transformed into the desired design by subjecting the 3D-printed item to specific conditions or forms of stimulation, such as heat, pressure, moisture, pH levels, wind, or light. In essence, 4D printing represents a progression from 3D printing technology, as it can now produce evolving objects. Additive manufacturing involves using 3D printers to create 3D models. However, there are limitations to this method, such as producing static products and having restricted build sizes. To address these challenges, four-dimensional printing was developed, which allows for the transformation of 1D or 2D strands into pre-programmed 3D shapes and the ability to metamorphose between dimensions. 4D printing builds upon 3D printing technology and expands beyond it. It is an emerging technology with the capability to fabricate complex structures. In this review, we explore the fundamentals of 4D printing, the factors that led to its development, the principles governing it, the components used, the 4D printing techniques, the challenges that must be overcome, and the future possibilities of 4D printing.