What on earth is 4D printing?!
I bet most of us are used to buzzwords these days. And, to many, including myself a little over three months ago, 4D printing just seemed like another one that would eventually be just forgotten. Like, how do you even 4D print something?. If this is you, then this article will (hopefully) help you be that bit less confused, as we will explore the basics of 4D printing, its applications and limitations in a little over 5 minutes, and, hopefully, demonstrate its a bit more than just a buzzword. So, let’s get to it!.
Dimensions & 3D printing.
Most of us have probably heard of 3D printing before. There are many different 3D printing methods, but, the most common one (FDL Printing) can be imagined as the process of printing a 2D shape, which has length and height, over and over again until it becomes thick and it gains width, the third dimension, hence 3D printing. This process of creating by adding layers of material on top of each other is called additive manufacturing (It has a really original name, I know).
Now, we could talk about 3D, but, as much as it is cool, it still isn’t the star of this article: That title goes to 4D printing. However, before we get deeper into it, it is important to understand what is meant by saying “4D”.
4D refers to 4 dimensions. However, it must be made clear that not all dimensions are created equal, and, glossing over some things that would make my physics teacher get mad at me, we can divide dimensions into two broad groups: Spatial dimensions and time dimensions. In the setting of 4D printing, there are three spatial dimensions: Height, length and width, just like 3D printing, and a time dimension, which is just time.
This means that what differences 3D printing from 4D printing is the usage of time. Now, I’m going to ask you to hang in there before you click out of the article for making you more confused than you already were, because things will begin to make sense soon.
Inorganic 4D printing
At the heart, the concept of 4D printing is simple, as it essentially is just a 3D printed object that changes its shape over time, meaning it can self assemble or even reshape completely. This is achieved by using smart, generally expandable materials between rigid ones within the 4D print, where these expandable materials will react to certain conditions, like light, temperature or water, causing them to expand or shrink, acting as joints and creating a desired shape.
4D printed structure folding over time
This development has a myriad of applications.
Some of the most direct and impactful ones can be seen in storage and logistics. Instead of storing 3D printed products, which tend to occupy large amounts of volume and be inefficient, 4D printed ones can have a storing shape that minimizes the space they take up, while still being easily assembled later on to their final shape by for example, spraying hot water over them, tackling the logistical efficiency of 3D printed objects. This could be particularly useful in situations where every square meter is valuable, such as space travel or sending aid to hard to access communities, helping them develop.
Another possible application is within liquid or gas pipes, wherein the pipes can actually grow to accommodate for large liquid or gas flows when all of its walls react with whatever the pipe is transporting. Similarly, 4D printing will also allow for these pipes to repair themselves, as if the expandable materials reacts to, for example, light coming from a gash in the pipe, it can expand and close said gash, saving millions yearly in repairs, reducing maintenance costs and ensuring that most issues with the piping will be solved before the repair crew even gets there.
These materials can also be used for clothing, where clothes may react to high temperatures or sweat and expand to increase breathability and help to deal with hot environments or maximize efficiency and comfort while doing sports or shrink themselves to help with colder climates, or shoes that slightly change shape when the users starts to run to increase comfort, amortization and efficiency, meaning 4D printing can kickstart the creation of a new type of adaptive clothing.
Lastly, another important application of 4D printing can be in fire detection and prevention, where high temperatures may activate 4D printed structures that then turn on sprinklers and the fire alarm instead of relying on smoke detectors, thus reducing false alarms and making sure the firemen are only called when they are really needed, or, in other cases, open small holes near windows in, for example, a burning house so that the smoke (Which is often the most dangerous part of a fire) escapes no matter if the window is closed or not, or expand designated and 4D printed fire proof doors so that the small spaces through which smoke may enter a room are sealed, protecting designated fire proof areas of the house and the people inside without the risk of asphyxiating to death.
However, the applications of 4D printing don’t end here.
Organic 4D printing
So far we’ve talked about inorganic 4D printing, which just means 4D printing with inorganic materials. However, the same way one may bioprint 3D hearts, livers or meniscuses in the future, certain organic materials, like specially made 4D bioinks (Which I must clarify, are still in development) can be printed, an the aforementioned smart or expandable an rigid materials do appear to have certain equivalents in organic ones (That, once again, are currently being developed), which may expand the reach of 4D printing enormously.
Imagine, if within your bloodstream you had 4D printed organic objects that, when they detect an increase in blood pressure, automatically change shape and release doctor prescribed ACE inhibitors, with a quantity proportional to the blood pressure rise being experienced. Or instead, if a person allergic to peanuts had 4D printed drug delivery systems that, when they detected X amounts of peanut traces, would reshape and immediately release epinephrine into the bloodstream to curb or outright stop the allergic reaction even before the worst effects took place.
These sorts of things might be possible and even commonplace in a not so far future, and the more we investigate and invest in this field the more applications that emerge. Still, it is also important to acknowledge the current limitations of the technology, as, let’s be honest, it is pretty easy to just see the good parts when riding a hype train.
Acknowledging Limitations
The main limitation of 4D printing is, unsurprisingly, that many of its potential applications are just that, potential, and based on speculation, particularly those related to organic 4D printing. We simply don’t know the limits of this technology yet, as it still is a rather unexplored field, and, though new advancements are being made at a fast pace, much of what is written in this article may simply be unfeasible at the industrial scales needed to revolutionize the world.
Similarly, another current limitation on the technology is the cost of 4D printed materials, as particularly expandable materials are relatively few and costly in the scales that will be needed if 4D printing is to be common in the future, though, as with most other technologies it is expected that these costs will lessen as new materials are created or perfected.
As the field of 4D printing is developed, these challenges will either be solved or prove themselves to be true limitants to the capabilities of 4D printing. However, this shouldn’t discourage us and make us forget the technology’s unrivaled potential and all the doors it opens, both for itself and other, apparently unrelated topics, like space travel.
In conclusion, the only thing that is certain is that this technology has a pretty realistic potential to become a cornerstone of human engineering and development (As 3D printing is quickly becoming) and open the door to thousands more innovations in the future, may they be related to space travel, human health or quickly and cheaply build infrastructure in developing communities, as, as I’ve hopefully shown so far, 4D printing is a bit more than “just a buzzword”.