4D Printing: Self-Assembling Sofas Revolutionize Industry

Imagine buying a flat sheet from a furniture store that changes into a sofa when you heat it with a hairdryer. Or consider the value of a stent that precisely expands inside a patient's artery, adapting to their unique anatomy.

Welcome to 4D printing, a frontier in material and manufacturing science that has been rapidly expanding over the past decade. While 3D printing has captured global attention for its ability to create objects layer by layer, 4D printing adds the element of time.

It involves 3D-printing adaptable objects from materials such as polymers or alloys that can bend, twist or transform entirely when they come into contact with heat or moisture. By moving beyond the constrictions of static designs, it opens up remarkable possibilities in areas such as medicine, aerospace, robotics and construction.

I was recently the lead author on a comprehensive report published in the journal of Smart Materials and Structures, charting the advances and challenges in this field. We outlined this industry's potential, offering a vision of a future where smart materials redefine design and manufacturing.

Here are some more of the main fields in which 4D printing could be transformative:

1. Healthcare

Like the stent I mentioned earlier, 4D printing raises the possibility of creating implants and prosthetics that adapt to patients' needs in real time. Research teams working on these innovations include the Biomet4D project, coordinated by the IMDEA Materials Institute in Madrid, which is developing smart, biodegradable metallic implants for people with seriously damaged or defective bones. The implants can change shape and expand as the bone grows, supporting it much more effectively than a static implant.

Another area of focus is smarter ways to give patients drugs. For example, a team of researchers based at China's Jilin University have created 4D-printed hydrogel capsules whose outer structure stays intact inside a patient's body until it reaches a particular temperature, such as when there is an infection, meaning the drug only takes effect when it's required. This could be useful in situations where it's beneficial to release a drug into a patient's body at exactly the right time and location.

2. Robotics and wearables

Integrating 4D materials into robotics and wearable devices enables them to adjust their functionality in response to their environment. For instance, researchers at Harvard University's Wyss Institute have developed self-folding robotic devices based on insights from origami that change shape when exposed to heat. One potential application could involve sending these devices to carry out tasks in environments that are difficult to reach, such as in deep seas or oceans.

Similarly, scientists at Deakin University in Australia are researching 4D-printing robotic joints with variable stiffness that can help with rehabilitation. For example, an arm could get stiffer when the user tries to pick something up, making it easier for them to lift it.

3. Exploring the cosmos

In the extreme conditions of space, adaptability is critical, so again there's a role for 4D-printed materials. For instance, Nasa's Jet Propulsion Laboratory uses 4D-printed metallic space fabrics.

These can fold, change shape and adapt to varying thermal and mechanical environments. This makes them suitable for a wide range of space applications, including shielding spacecraft from meteorites, insulating against extreme temperatures and conforming to uneven terrain on Jupiter's smallest moon, the icy Europa.

Challenges and opportunities

The current capabilities of 4D printing are nothing short of remarkable, yet the field still faces significant challenges. While we can now create materials that transform with precision, there's still more research required to ensure they're biologically safe and durable for the long term.

Also, scaling up production to meet industrial demands, particularly for high-resolution designs or nanoscale structures, requires not just new techniques but also new ways of thinking about manufacturing. Cost is another barrier - specialised materials and processes can often prove too expensive at present for widespread use.

And yet, the promise of 4D printing is tantalising. One of the big attractions is in sustainability. From water pipes that adjust flow rates to buildings that self-regulate carbon dioxide levels, 4D printing creates the potential for adaptive systems that help in this area. A prime example is the Solar Gate , developed by the University of Stuttgart's Institute for Computational Design and Construction.

Inspired by the way that pine cones open in response to sunlight, the gate consists of a series of 4D-printed cellulose flaps that can be installed into buildings to open and close in response to certain levels of humidity and temperature. They curl upwards in winter to allow heat in, and flatten in the summer to block direct sunlight. It demonstrates how a building can be made more energy efficient without relying on an external source of power for, say, air conditioning.

Meanwhile, artificial intelligence is already accelerating progress by optimising the design and behaviour of 4D-printed objects. It is helping researchers to have more precise control over how these smart materials respond under different conditions, without having to rely so much on trial and error.

This is still a young industry, with limited venture capital investment and a workforce that is only beginning to take shape. But as more research institutions and companies recognise its potential, the pace of innovation should quicken. According to one report , the sector is due to grow at around 35% a year over the next five years.

We are now developing structures that recover or change their shape on demand at the 4D materials and printing laboratory at Nottingham Trent University and the 4D Printing Society . For example, we've already 4D-printed medical stents that can self-expand in response to body temperature (see images below).

We're also developing materials for boat fenders and car bumpers whose shape can be restored by adding heat, as a way of removing dents, as well as shape-adaptive finger splints for broken bones, and self-assembling, extra-comfortable furniture .

So, the next time you marvel at the capabilities of 3D printing, remember: the future lies in 4D printing, where materials come alive and redefine the possibilities of tomorrow.

Mahdi Bodaghi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.