Experts: Christian Leinenbach (Empa), Marius Wagner (ETH Zürich)
4D printing is a technology that could become a game-changer in many fields, but is currently still in its infancy. As industrial implementation is still in the distant future, its potential for the Swiss economy is still unclear.
Image: ETH Zurich
4D printing is a sub-field of additive manufacturing. Like in additive manufacturing, objects created with this technology are assembled layer by layer. However, they change shape over time after printing. This is made possible by active materials (see Showcase Earthquake protection in four dimensions) that deform in a specifically desired manner when exposed to a magnetic or electric field, or else to a stimulus such as heat, light or water.
Thus, 4D printing is a collective term for combining additive manufacturing with materials that have specific properties. Indeed, it would be more accurate to use the term ‘additive manufacturing with active materials’ rather than ‘4D printing’. 4D printing encompasses numerous disciplines, ranging from chemistry to materials science, and from conventional engineering disciplines to architecture and design.
The combination of active materials and additive manufacturing allows the production of groundbreaking new structures, as it makes it possible to precisely define where which material, with which property, is used. This benefits developments in the field of metamaterials, for example, i.e. artificially produced materials with optical, electrical or magnetic properties that do not occur in nature, such as stealth coatings for fighter aircraft. 4D printing’s wide range of geometries and materials could make it a game-changer in various fields. For instance, additively manufactured active structures could be used in the construction industry as facade elements that adapt to the weather. Another potential application in construction is the production of bistable formwork shapes using composite materials that are stable in two states. These are substances comprising two or more bonded materials that, when combined, have different material properties to the individual components. Such formwork shapes could be efficiently manufactured using 4D printing.
In the energy sector, 4D printing allows the production of joints for solar cells that optimally align themselves with the sun’s rays. In aerospace, it gives rise to applications such as weather-related performance optimisation using 4D-printed wings. Folded structures that do not unfold until they reach outer space are also conceivable. Thanks to additive manufacturing, 4D-printed stents could be adapted to the patient and inserted into vessels in a compressed form, where they then unfold into their final shape.
The potential of 4D printing is great, as it promises numerous advantages compared to conventional manufacturing: incorporation of active materials into complex structures, miniaturisation and resulting improvements in resource efficiency. However, only biomedical applications are as yet close to being product-ready. For most other applications, there is still a need for material-related developments before it will be possible to move ahead with implementation in products. Industry is interested and willing to invest, but the time is not yet ripe for industrial implementations. Moreover, the potential for the Swiss economy is not clear at present. In the field of material and process development, as well as in biomedical applications, Switzerland is well positioned to turn the possibilities into real opportunities.
The main risks have to do with material development. Current studies only cover concepts and still largely fail to address issues associated with scalability and reliability of materials. Furthermore, the procedure is still only functional at laboratory scale and cannot yet be scaled up: It remains to be seen whether the grand visions are achievable. As a further complication, the certification requirements for new types of materials constitute a regulatory barrier that affects biomedical and aerospace applications in particular. Societal obstacles, such as acceptance problems, are not to be expected.
On a technical level, there are major challenges involved in the processes and in material development. It would be ideal if plastics, metals and other materials could be printed together in one process step. Due to the differing material properties though, this is not yet possible: Plastics, for example, burn when materials like metals are just starting to melt. In addition, the properties of active materials are not ideal for printing; rigidity, durability, longevity and structural efficiency are issues that still need to be addressed. Not only are material developments needed, but also process innovations and optimisations. Thus, a great deal of research is required.
The procedure is not yet sufficiently developed to be of interest to SMEs. Most activities are limited to academic research and there are no firms offering relevant support or services.
Comprehensive and further information on the subject can be found in the article Earthquake protection in four dimensions.
