Three-dimensional (3D) printing, a form of additive manufacturing, has caused quite a stir in the industrial manufacturing sector. Although the technology is still developing, researchers at MIT have already come up with the concept of four-dimensional (4D) printing. Could this be the next big thing in manufacturing?
3D printing technology
The incredible 3D printing technology was developed by Charles W Hull in 1983 and has since seen rapid wide-ranging applications. In this type of printing, the hardware is made to deposit material, layer upon layer, in precise geometric forms to create an object using 3D object scanners or data computer-aided-design (CAD) software. It is unlike conventional manufacturing or subtractive manufacturing, where the material is removed by using milling, machining, carving, shaping, etc. to create an object.
The advantages of 3D printing are for all to see. From small components to aerospace equipment, its applications are ever expanding in various fields. From a simple production process, it now supports convergence technologies, used in food packaging, jewelry and equipment, and high-tech sectors covering aerospace, architecture, automotive industry, education, medicine, military, etc.
4D printing technology
Like 3D printing, 4D printing is also based on Stereolithography (SLA), which builds 3D objects, layer upon layer, using smart materials, such as photo-polymeric liquid. In the 4D printing process, a smart 3D object is created from smart materials that can change their shape over time, if exposed to water, heat, light, current or magnetic field.
This transformation of material over time is the fourth dimension. This means that 4D printing technology combines 3D printing, smart materials and customized design that is required for transformation. In this type of printing, the structure of the object can be preprogrammed as desired and designed to assemble itself.
Difference between 3D printing and 4D printing
The following are the differences between the two types of printing:
● Manufacturing techniques
The 3D printing technology involves new manufacturing techniques, such as FDM (Fused Deposition Modeling) and SLA (Stereolithography), as opposed to conventional manufacturing methods, such as CNC machining, casting, plastic injection, etc. These 3D techniques produce objects whose shape is permanent and will remain unchanged after production.
Although 4D printing technology also uses the techniques of 3D printing, the objects so created with advanced materials and customized designs have the capability for structural transformation. However, exposure to external stimuli, such as water, heat, current or light, is needed to commence the deformation phase.
● Materials
The types of materials used for layer upon layer process differs between the two types of printing. In 3D printing, the end product can either be rigid or flexible, that is, capable of regaining shape once the load is removed from it. This is much like a rubber band that can be stretched, but comes to its original form, when at rest.
In 4D printing, the smart material transforms itself under exposure to stimuli. The smart structure can be of two types – the rigid materials can be wholly made from expandable materials or may be connected with expendable elements. Once these expendable elements get exposed to certain stimuli, they change shape by moving or rotating, thereby transforming into a new shape. Such smart materials include hydrogel, which is capable of absorbing a large quantity of water and expand, and polymeric material that can return to its original shape from a deformed state.
● Size of the object created
The size of the object created with the help of 3D printer depends upon the size of the printer. However, in 4D printing, the size of the object can exceed the printer’s dimensional limitations. To understand how this takes place, imagine flat cardboard and a folded cardboard. In 3D printing, you will need to directly print a folded cardboard, whereas, through 4D printing, you only need to produce a flat object that later transforms itself into a folded cardboard.
Conclusion
Whereas 3D printing technology has proved to be highly versatile and efficient with regard to design, fabrication and applications, 4D printing has potential to add value in certain applications. It may never become as mainstream as ‘normal’ 3D printing, but it will be interesting to watch its development, as well as the impact it has on the area of smart materials.
