4D filaments 

4D filaments

The name 4D refers to a fourth dimension achieved in the post-processing of the 3D printed parts with these materials. Inspired by the principle of self-assembly, 4D printing is the process through which a 3D printed object is transformed into a different structure by the influence of external energy input such as temperature, light or other environmental stimuli.
The available 4D filaments are of three types:

• SMP or shape memory polymers
• LCE or liquid crystal elastomers: as they contain liquid crystals sensitive to heat, their shape will be modified under the effect of temperature
• Hydrogels: due to their biocompatibility, these polymer chains, formed mainly by water, are used on medical applications

SMP

Polymers with shape memory, which remain rigid at room temperature and offer special properties when they reach the glass transition point. An example would be the TPU SMP from Convena: a 4D filament with a composition based on TPU (thermoplastic polyurethane) that allows post-processing with which to modify the shape of the 3D printed parts. Thanks to its special composition and SM technology, the pieces printed with this filament can be manually modified, allowing them to acquire another shape and maintain it over time.

Applications

Pipes that fix themselves automatically when they crack, prostheses that adapt to growth or clothes that change depending on the environment are some of the examples that we can obtain through 4D. In the transport sector, companies such as BMW (in collaboration with MIT) have presented a material that changes under the effect of air pulses; this could lead to wheels capable of solving problems such as punctures. The aeronautical industry is not far behind, with components that react to atmospheric pressure or fabrics for space suits capable of reflecting heat outside and keeping it inside. It is perhaps in the field of regenerative medicine and the manufacture of cellular structures where the applications are most fascinating. In this case, 4D printing offers the possibility of creating bespoke, intelligent and evolving elements; such as, cells that adapt to the human body or devices that intelligently release medication, in case the patient needs it.