The fourth dimension to 3D printing

Adding the fourth dimension to 3D printing

As 3D printing continues to revolutionize manufacturing, researchers have decided that three dimensions are not enough, and so the concept of 4D printing has begun to emerge. These four-dimensional objects are still built layer by layer in a 3D printer. But given time – the fourth dimension – these devices can automatically morph into a different shape, and thereby even change their function.

So far, researchers have developed devices using materials that are actuated by water or heat. This is significant, since the structures are ready as soon as you pick them up from the printer. However, up until now, the prototypes developed were slow, severely limited in the amount of times they could be used, and weak, since they relied on a bending motion in a flexible material.

Professor Marc in het Panhuis and PhD student Shannon Bakarich are set to change all that. The University of Wollongong researchers are the first to use a process whereby four different materials were printed simultaneously. The hydrogels used by the team consist of a network of poly N-isopropylacrylamide (PNIPAAm) and alginate. Alginate is a salt of alginic acid that is commonly found in seaweed and algae. Among other things, it is used as a thickener in food. PNIPAAm consists of two polymer networks entangled in one another. This gives the material strength and durability. When cracks form in one network, the other network bridges the gaps and so prevents greater damage.

4D printing 3D printing

The dual-network structure is not unique to PNIPAAm. However, the researchers used PNIPAAm since it exhibits a large change in volume at a critical temperature of about 32-35° Celsius (90-95° F). This change in volume is caused by a transition of the polymers from a collapsed globule state to an expanded coil state. When the temperature goes down, the polymers collapse back into globules.

The researchers combined thin sections of PNIPAAm with traditional materials. This allowed them to create a design capable of relatively fast linear motion, much like the contraction of a muscle. Best of all, this process is reversible. The transition can be actuated by different stimuli, depending on the hydrogels used.

Using PNIAAm, the researchers have developed a functioning valve that responds to the temperature of the water surrounding it. “It’s an autonomous valve,” says Panhuis in a statement. “There’s no input necessary other than water.” An autonomous device like this is valuable in medical soft robotics. As soon as the surrounding water reaches a certain temperature, the polymer strands inside the hydrogel change their shape. The large change in volume in the hydrogel causes a strong linear motion, which closes the valve.

Combining smart materials and 3D printing in this way offers an exciting method of creating custom designs of small autonomous devices. “The cool thing about it is, it’s a working, functioning device that you just pick up from the printer,” Panhuis said. Maybe we will one day even be able to print our own self-assembling structures and soft robots.

by  | May 24, 2015 at 9:30 am

4D printing vs 3D printing

Professor Marc in het Panhuis holds a 4D printed valve that can change shape.

4D printing is cooler than 3D printing, and why that means the end of IKEA flatpacks

Just as you got used to the idea that toys, homewares, even guns can be built with 3D printers, the next phase is upon us. Researchers, including Australians, are already building objects with 4D printing, where time becomes the fourth dimension.

“4D printing is in essence 3D printed structures that can change their shape over time,” said inventor and engineer Marc in het Panhuis​. “They’re like transformers,” he says.

And their applications will be limitless. Imagine medical devices that can transform their shape inside the body, water pipes that expand or contract depending on water demand and self-assembling furniture.

Professor in het Panhuis’ team at the ARC Centre of Excellence for Electromaterials Science, located at the University of Wollongong, have just built an autonomous valve that opens in warm water and closes in cold water.

The valve is made out of four types of hard or soft hydrogels – networks of polymers – fabricated at the same time using a 3D printer.

Inside the valve’s structure a series of actuators respond to hot or cold water to open and close the valve.

While the valve’s shape change is activated by water, other 4D printed devices transform by shaking, magnets or changes in temperature.

“It’s a widely expanding field,” Professor in het Panhuis said.

“You can buy jewellery that’s 3D printed and changes shape when you put it on,” he said.

US inventor Skylar Tibbits, who runs MIT’s Self-Assembly Lab and coined the term 4D printing, is exploring 4D printing to manufacture furniture that can build itself.

“Rather than receiving a flat-pack and getting your screwdriver out, what he’s postulating is what if you just add a bit of water to it and it assembles itself,” Professor in het Panhuis said.

While its early days, the group are more advanced in their designs of pipes that can change their capacity, expanding and contracting when water demands increase or drop off.

The military is another industry interested in objects that can change shape or self destruct,Mission Impossible style.

“When armies are on the battlefield they leave a lot of electronics behind. What if you could make 3D printed electronics that [once the soldiers leave] undergo transient behaviour once they become too hot, or too cold, or too wet so they completely disappear so the enemy can’t use any of your materials,” Professor in het Panhuis said.

In 2012 DARPA researchers created implantable medical device that could deliver anti-microbial treatment to a wound site but would dissolve when no longer needed.

The electronic devices were made of ultra-thin silicon, magnesium and silk that could dissolve in the body, reducing the risk of a secondary site infection.

by , Science Editor | April 22, 2015