Impresión 4D:El futuro de la impresión 3D

¿Y si las tuberías pudieran repararse automáticamente? si se agrietan o rompen, o la ropa podría cambiar según el clima o la actividad que el usuario esté realizando ? Muebles que se ensamblan solos, prótesis que se adaptan al crecimiento... Estas son solo algunas de las posibles aplicaciones que la tecnología de impresión 4D pretende realizar.

Imagen 1:Garra impresa en 4D modificando su forma. Fuente:Sculpteo.

Impresión 3D ha existido por casi 30 años y mientras todavía está en proceso de investigación, descubriendo nuevos materiales y aplicaciones, han surgido nuevas tecnologías como 4D.

En el Laboratorio de autoensamblaje del MIT , han desarrollado un proyecto del que forma parte la impresión 4D. Su propósito es combinar tecnología y diseño para inventar materiales programables y tecnologías de autoensamblaje con el objetivo de reinventar la construcción, la fabricación, el ensamblaje del producto y el rendimiento. Mientras tanto, un estudio del Instituto Wyss (parte de la Universidad de Harvard) ha conseguido imprimir un objeto que, cuando entra en contacto con el agua, cambia de forma e, resultando en una especie de florecimiento de sus extremos. Desarrollaron un material basado en estructuras naturales, como las plantas, al que se inyectaron fibras de celulosa durante el proceso de impresión.

Video 1:Arquitectura que cambia de forma. Fuente:Universidad de Harvard.

¿Qué es la impresión 4D?

Inspirada en el principio del autoensamblaje, la impresión 4D es el proceso mediante el cual un objeto impreso en 3D se transforma en una estructura diferente por la influencia de la entrada de energía externa, como la temperatura, la luz u otros estímulos ambientales. Es decir, obtener un objeto a través de la tecnología 3D que, gracias a las propiedades del material del que está hecho, es capaz de cambiar cuando se somete a un estímulo ambiental.

Esta es precisamente la diferencia entre la tecnología 3D y 4D:la capacidad de los objetos para transformarse con el tiempo sin intervención humana.

Materiales utilizados

La clave de la impresión 4D no es tanto el proceso , basado en las impresoras 3D familiares, pero los materiales. Como se trata de una tecnología bastante nueva, los materiales disponibles no son tan variados como los que se utilizan para la impresión 3D estándar. Sin embargo, hay algunos muy interesantes.

SMP (polímeros con memoria de forma)

Polímeros quepermanecen rígidos a temperatura ambiente y ofrecen propiedades especiales cuando alcanzan el punto de transición vítrea. Un ejemplo sería el TPU SMP de Convena:un filamento 4D con una composición basada en TPU (poliuretano termoplástico) que permite el posprocesamiento para modificar la forma de las piezas impresas en 3D. Gracias a su especial composición y a la tecnología 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.

Aplicaciones

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, por ejemplo. 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.