WELCOME TO THE FUTURE OF 3D... 4D!

What if the tubes could fix themselves automatically without cracking or breaking?

What if clothes could change according to the weather or the wearer's activity?

Furniture that assembles itself... prostheses that adapt to growth...

But the truth is that these are just some of the possible applications that 4D printing technology envisions.

3D printing has been around for almost 30 years and when it is still being developed and in an accelerated and deep research process, new materials and applications and new technologies are being discovered... such as 4D.

At the MIT Self-Assembly Lab, this 4D printing project grows and develops. Its aim is to combine technology and design to invent programmable materials and self-assembly technologies with the aim of reinventing construction, manufacturing, product assembly and performance.

Meanwhile, at the Wyss Institute, Harvard University, it was possible to print an object that, when it comes into contact with water, changes its shape, resulting in a kind of flowering of its extremities – mind blowing!! At this institute, they developed a material based on natural structures, such as plants, which was injected with cellulosic fibers during the printing process.

What is 4D printing?

Inspired by the principle of self-assembly, 4D printing is the process by 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, i.e. obtaining an object through 3D technology which, thanks to the properties of the material from which it is made, is able to change when subjected to an environmental stimulus.

This is precisely the difference between 3D and 4D technology: the ability of objects to transform over time without human intervention.

Materials used

The key to 4D printing is not so much the process, based on popular 3D printers, but the materials. As this is a fairly new technology, the materials available are not as varied as those used for standard 3D printing. However, there are some very interesting ones.

SMP (Shape Memory Polymers)

Polymers that remain rigid at room temperature and that offer special properties when they reach the glass transition point. An example is Convena's TPU SMP: a 4D filament with a TPU (thermoplastic polyurethane) based composition that allows post-processing to modify the shape of 3D printed parts. Thanks to its special composition and Shape Memory Polymer technology, parts printed with this filament can be manually modified, 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 with hot water until it reaches its glass transition temperature. At this point, the piece softens and the user can easily change its shape. Once cooled, the part retains its 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 glass transition temperature of the material is reached again.

LCE (Liquid Crystal Elastomers)

They contain liquid crystals that are sensitive to heat.

By controlling its orientation, the desired shape can be programmed: under the effect of temperature, the material will relax and transform according to the dictated code.

hydrogel

Polymer chains consisting primarily of water, particularly used in photopolymerization processes. The latter are concentrated in the medical sector due to their biocompatibility.

In addition, some 4D printing processes may use various materials, mainly composites such as wood or carbon, which are added to SMP or hydrogel.

This results in objects with hard and moving areas.

4D SHAPESHIFTING ARCHITECTURE

applications

Given the many advantages of these smart materials, the applications of 4D printing are numerous.

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 adapt to the environment, would allow modifying and improving interior conditions.

Medicine

In this case, 4D printing offers the possibility to create custom-made, intelligent and evolutionary devices. For example, when printing a 4D implant, its status and viability could be more easily monitored once it has been 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 drugs, it would be possible, for example, to print a device that would deliver the necessary 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 pulses of air. The applications are very interesting, because in the future we may have tires that can repair themselves in the event of a puncture or adapt to the terrain and weather conditions of the environment.

In the case of the aeronautical 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 hydraulic hinges and actuators, significantly lightening the devices. In addition, it is also working on the development of thermo-reactive materials to cool aircraft engines.

Raúl Pulido Casillas, a Spanish engineer, created a 4D-printed smart fabric for NASA. The metallic mesh, made of pieces of silver joined together, has thermal regulation programmed in its printing. In other words, not only its form was printed, but also the function of the materials. As it is able to reflect heat on the outside and retain it 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 color depending on the environment, or that regulate perspiration depending on the soldier's pulse or ambient temperature.

Although still in its infancy, 4D technology will revolutionize the manufacture and nature of objects for years to come, just as 3D printing did in its day.

4D PRINTED PROGRAMMABLE MATERIALS