In this episode, we speak with plastics expert Andy Pye about the state of 4D printing, including:
- How 3D printing and and 4D printing are inexorably connected
- What applications does 4D printing have?
- What materials are used in 4D printing?
- When will 4D printed products be available commercially?
- What are some challenges facing 4D printing engineers?
- What's next in 4D printing technology?
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Angie: Let's just jump right in. So you've written a number of articles for the Knowledge Center on 4D printing, and those articles have given a background on the innovations and kind of what it is. But why don't you go ahead and explain what it is, and how it's different or an expansion on 3D printing.
Andy: Yep, absolutely. Well, as you say, we've written three articles on it. And I came across it, first of all, I guess in 2013. So it's not that long ago. And the articles we've written have created a huge amount of interest I think, because it's such a futuristic technology. Four-D printing, in effect, is a development from 3D printing, which people will be much more familiar with. And 3D printing is otherwise known as additive manufacturing, or, when I was a kid, it was known as rapid prototyping. But that phrase seems to have somewhat gone out of fashion now.
And basically what it is, is a means of manufacturing items out of, not necessarily just polymers, it can be metal powders as well, layer by layer, by a number of different techniques, of which probably the most familiar is a technique called stereolithography. So that's 3D printing. And 3D printing and 4D printing are inextricably interlinked. So we'll be talking about both of them together.
So what's different about 4D printing? Well, essentially you take a 3D printed object and then once it's out of the production process, you then provide a stimulus to encourage it to change its properties in some way. Maybe change shape or change one of its other properties. And the stimulus might be heat, it might be water, it might be light. It could even be pressure or current or something like that. So there's a fourth dimension, which is usually a shape change, which is time-dependent after the initial manufacture. And that's what the fourth dimension means.
So, a common kind of example from sort of olden days might be shape-memory alloys, which use temperature changes to cause changes in material shapes. And they've been around for a very long time. So that's kind of a similar idea to 4D printing. And some aspects and some applications of 4D printing do use the shape-memory effect.
We might also use things with electroactive polymers, which use catalysts to activate polymers with pressurized fluids, gasses, or even light. So, and other 3D printed structures might use moisture. So there's a whole range of different possibilities, pretty much all of which are still in the research stage.
Coming back quickly to that fourth dimension, we're often quite used to the idea of time being a fourth dimension, you know, with three dimensions of X, Y, and Z being movement directions, and time being the fourth. So here we're using the fourth dimension in effect to be the time taken for a self-transformation after manufacture. Because of that, some industry commentators like to use the term "3D printing and self-assembly" as an alternative to "4D printing." So that's a pretty long explanation of what we mean.
Angie: Well, it's a great background and kind of baseline to get people all on the same page on what we're talking about. So I think you mentioned a couple of examples. But what other kinds of applications does the technology have?
Andy: Yep. Well, that's a good question. And perhaps it's better to ask what applications might the technology have.
Angie: Right. True, since it's still in research.
Andy: Yeah. A lot of it is in research. The ideas really came out of MIT as much as anywhere. But you'll find Georgia Institute of Technology is quite predominant as well. So is the Singapore University. And there are other researchers in Australia and even the University of Bristol here in England, also active in various aspects. And most of them are looking at different little parts of how this whole thing works together with sort of different specialized technologies.
So, one area that's very excited by it is the medical engineering area, because they can see, for example, how components like stents to band arteries could be manufactured by 3D printing and then be made to expand when in situ. So that's an example. Another medical application is printing new skin for skin grafts which could then be, you know, encouraged to freely change shape over time. So, medical is a big area. Third area of medicine would be using drug capsules that release medicine at the first sign of infection...
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