Impression 4D :L'avenir de l'impression 3D

Et si les tuyaux pouvaient se réparer automatiquement s'ils se fissurent ou se cassent, ou si les vêtements peuvent changer en fonction de la météo ou de l'activité de l'utilisateur ? Des meubles qui s'assemblent tout seuls, des prothèses qui s'adaptent à la croissance... Ce ne sont là que quelques-unes des applications possibles que la technologie d'impression 4D est censée réaliser.

Image 1 :Griffe imprimée en 4D modifiant sa forme. Source :Sculptéo.

Impression 3D existe depuis près de 30 ans et bien qu'il soit encore en cours de recherche, de découverte de nouveaux matériaux et applications, de nouvelles technologies telles que 4D ont émergé.

Au Laboratoire d'auto-assemblage du MIT , ils ont développé un projet dont l'impression 4D fait partie. Son but est d'allier technologie et design pour inventer des matériaux programmables et les technologies d'auto-assemblage dans le but de réinventer la construction, la fabrication, l'assemblage des produits et la performance. Parallèlement, une étude du Wyss Institute (partie de l'Université de Harvard) a réussi à imprimer un objet qui, lorsqu'il entre en contact avec l'eau, change de forme e, résultant en une sorte de floraison de ses extrémités. Ils ont développé un matériau à base de structures naturelles, telles que les plantes, qui a été injecté avec des fibres de cellulose lors du processus d'impression.

Vidéo 1 :Architecture à changement de forme. Source :Université de Harvard.

Qu'est-ce que l'impression 4D ?

Inspirée du principe d'auto-assemblage, l'impression 4D est le processus par lequel un objet imprimé en 3D est transformé en une structure différente sous l'influence d'un apport d'énergie externe tel que la température, la lumière ou d'autres stimuli environnementaux. C'est-à-dire obtenir un objet grâce à la technologie 3D qui, grâce aux propriétés du matériau à partir duquel il est fabriqué, est capable de changer lorsqu'il est soumis à un stimulus environnemental.

C'est précisément la différence entre technologie 3D et 4D :la capacité des objets à se transformer dans le temps sans intervention humaine.

Matériaux utilisés

La clé de l'impression 4D n'est pas tant le processus , basé sur les imprimantes 3D familières,mais les matériaux. Comme il s'agit d'une technologie relativement nouvelle, les matériaux disponibles ne sont pas aussi variés que ceux utilisés pour l'impression 3D standard. Cependant, il y en a quelques-uns très intéressants.

SMP (polymères à mémoire de forme)

Des polymères qui restent rigides à température ambiante et offrent des propriétés particulières lorsqu'ils atteignent le point de transition vitreuse. Un exemple serait le TPU SMP de Convena :un filament 4D avec une composition à base de TPU (polyuréthane thermoplastique) qui permet le post-traitement pour modifier la forme des pièces imprimées en 3D. Grâce à sa composition spéciale et à la technologie Shape Memory Polymer, parts printed with this filament can be modified manually, allowing them to acquire another shape and maintain it over time.

The process of modifying the shape of a 3D printed part with SMP TPU filament consists of placing the 3D printed part in a container of hot water until it reaches its glass transition temperature. At this point, the part softens and the user can easily modify its shape. Once cooled, the part maintains the acquired shape and remains stable. In addition, parts 3D printed with SMP TPU filament can be restored to their original shape by reversing the process. In other words, the material's glass transition temperature is reached again.

LCE (liquid crystal elastomers)

They contain liquid crystals that are sensitive to heat. By controlling their orientation, the desired shape can be programmed: under the effect of temperature, the material will relax and transform according to the dictated code.

Hydrogels

Polymer chains consisting mainly of water , particularly used in light-curing processes. The latter are focused on the medical sector due to their biocompatibility.

In addition, some 4D printing processes can use various materials, mainly composites such as wood or carbon, which are added to SMP or hydrogels. This results in objects with rigid and movable areas.

Applications

Given the many advantages of such intelligent materials, the applications of 4D printing are innumerable.

Construction

The construction of climate-adapted structures such as bridges, shelters or other facilities would be a huge step forward in this field. 4D bricks capable of modifying walls and roofs to suit the environment would allow indoor conditions to be modified and improved.

Video 2:Programmable wood. Source:Self-Assembly Lab, MIT.

Medicine

In this case, 4D printing offers the possibility to create tailor-made, intelligent and evolving devices. For example, by 4D printing an implant, its condition and viability could be more easily monitored once it is integrated into the patient.

This concept is applicable to all regenerative medicine and the fabrication of cellular structures. 4D printing would allow cells to adapt to the human body depending on its temperature, for example. If we talk about medicines, it would be possible, for example, to print a device that would release the required dose depending on the patient's body temperature.

Transport

A few months ago, BMW and MIT presented their inflatable material, which changes shape and size under the effect of air pulses. The applications are very interesting, as in the future we could have tyres that can repair themselves in case of a puncture or adapt to the terrain and weather conditions of the environment.

In the case of the aircraft industry, a 4D printed component could react to atmospheric pressure or temperature changes and thus change its function. Airbus is currently working on such developments, as these components could replace hinges and hydraulic actuators, significantly lightening the devices . In addition, it is also working on the development of heat-reactive materials to cool its aircraft engines.

Raúl Pulido Casillas, a Spanish engineer, has created a 4D-printed smart fabric for NASA. The metallic mesh, made of silver pieces joined together, has thermal regulation programmed into its print. In other words, not only its shape has been printed, but also the function of the materials. As it is able to reflect heat on the outside and retain it on the inside, it could be an ideal element for making astronaut suits or covering spacecraft.

Fashion

In the textile industry, 4D printing is also finding its place. The possibility of printing shoes that adapt to movement, impact, temperature and atmospheric pressure is a possibility. The US military has already made a foray into this field and is testing uniforms that change colour depending on the environment, or that regulate perspiration depending on the soldier's pulse or the ambient temperature.

Although we are still in its infancy, it is certain that 4D technology will revolutionise the manufacture and nature of objects over the next few years, just as 3D printing did in its day.