Textiles evolve by themselves

If a pair of jeans lets in ventilation in summer (intentionally!) without any help from its wearer, we are talking about a ‘4D textile’ – for some people, this is the next generation of textiles. David Schmelzeisen from the Institute of Textile Technology (ITA) at RWTH Aachen University explains what it’s all about.

David, we know 3D from cinema and television, and there are even 4D cinemas where aromas, wind, fog, drizzle and moving elements are used in the seat upholstery. But what are we to understand by 4D textiles?

Objects that we come across in everyday life have three dimensions: length, width and height – in other words, 3D. Added to these, we have time as a fourth dimension. In terms of textiles, we can broadly say this: it’s all about products which change their form under certain ambient conditions in a planned, intentional way. Let me illustrate this with the example of a tight pair of jeans: if they become baggy, it can be because of a change over the course of time, but we are not talking about a 4D textile here, because it is not a process that has been planned. If however the jeans were to expand slightly on a warm summer’s day and the textile structure provide air to cool the legs, because this is what we have ‘programmed’ them to do, this would be a 4D effect.

What do you mean by ‘programmed’?

4D textiles are a combination of textile base materials and microstructures, which are printed on the fabric surface in the form of thin plastic layers. The change of form desired later is programmed directly into the textile.

How then is a transformation like this set in motion?

We work primarily with heat (as with the jeans and summer heat) and moisture, but we are also experimenting with UV and laser radiation, and changes in pH levels. Electric and magnetic fields could also function as stimuli.

And what could they activate?

Movement, for example, as in the case of textile facades or stadium roofs, which open and close by themselves when exposed to heat or moisture. Or pulsating vascular supports (stents) which expand and contract in the body according to blood flow. Football shoes, which change their surface when they touch the ball, also spring to mind. All these are still under research, but the possibilities are practically unlimited.

What makes your 4D approach distinct from ‘smart textiles’ which change their state by means of electronics?

These textiles are made ‘smart’ or ‘intelligent’ with sensors and microchips, which can often lead to an extreme increase in complexity. This can put too much strain on the consumer. We want to make things simpler by programming the intelligence, i.e. the desired change, directly into the textile material with the microstructures – without technology and electronics.

What materials do you work with?

Primarily with woven knits, i.e. knitted or crocheted fabrics, which are nice and stretchy, but in general all elastic and porous textiles are suitable. For the microstructures, we use different plastic materials, and combine them with each other in the 3D printing. Combining them is important because they all react differently to ambient conditions; whilst one kind of plastic will stretch significantly in reaction to moisture, another won’t change at all. Tensions arise where the two materials come together, and these trigger a macroscopic movement in the textile – this is the 4D effect that we use.

Can you explain this in a little more detail?

We stretch the textile first and then print it with the microstructures. To do this, we use widespread 3D processes, such as digital light processing and fused deposition modelling. Thus, the microstructures are printed on pre-stretched textile fabrics, where they form a kind of structure that can be seen as an energy store, a little like a tensioned spring. They stay there in the textile until they are activated by moisture, heat or other triggers and change their tensioned state, and thus that of the textile – et voilà: the jeans fabric opens up in the heat and lets cool air in.

Some experts call 4D textiles the next generation of textiles. Why?

Up till now textiles were seen as static materials. 4D products, on the other hand, can adapt to suit their environment and react to changing conditions. This means that we’ll be able to interact with the environment through our clothes in future. I think that the 4D approach to textiles will make many of the sensors, microchips and actuators in ‘smart’ clothing and technical textiles superfluous in the next few years.

Title image: source: ITA