The Martian: 4D Printing Our Way to Mars
By: Valkyrie Holmes
Tags: Engineering, Future, Space, 3D Printing, Mars

The Martian: 4D Printing Our Way to Mars

By Valkyrie Holmes

Elon Musk wants a million people on Mars by 2050. With the most dependable travel window open only every 26 months, how is this achievable?

There’s a lot to be discussed about space travel, specifically in traveling to Mars but one of the biggest technological advances of our time can solve a lot of those issues. I’m talking about 3D and 4D printing.

Most readers would already recognize the term “3D printing” but for those who don’t, I’ll give you a brief rundown. 3D printing refers to the process of depositing materials under computer control to create a three-dimensional object, most commonly by stacking layers of metals or plastics together to create a solid figure. They’ve been used to print prosthetics, houses, and even human body parts with the help of bioprinters. You can read all about that here.

But in this article, I’d like to focus a bit more on 4D printing.

Adding Another Dimension

First, let’s define 4D printing. 4D printing is a manufacturing technique that uses 3D printing to layer textures and geometries into one product or design. This could be multiple levels of self-assembly or shape-shifting. The final product could even contain multiple properties like reflecting and absorbing heat.

One of the first experiments ever done on 4D printing was back in 2018 from researchers at the Georgia Institute of Technology where they created objects that expanded when exposed to heat or water. They called them tensegrity structures and they relied on struts, floating polymer rods, held together by cables. Each strut had a preprogrammed “memory” engrained inside them which is what controlled the speed of unfolding. They predicted usage in foldable antennas in space that reacts with the heat of the sun or for structures in shape-changing soft robots.

“[Tensegrity structures] are extremely lightweight while also being very strong… The goal is to find a way to deploy a large object that initially takes up little space.” -Glaucio Paulino, Professor at Georgia Tech’s School of Civil and Environmental Engineering

When we reference videos about 4D printing, a lot of it has to do with objects being foldable on command or due to some external stimuli. That could be temperature, light, water, or other environmental triggers. The bottom line is that it combines tech and design with self-assembly and programmable materials.

You might be thinking, our world is already in 3D; what’s the other dimension?

The answer: time.

In most cases, scientists use commercial 3D printers like Polyjets to print 4D models but their choice of material is different. The input has new properties that can remember their shape or be programmed to transform over time in response to external factors. We have:

Thermo-responsive materials that work on Shape Memory Effect (SME) when exposed to a change in heat or temperature. They can come in alloys, polymers, hybrids, ceramics, and gels.

They can come in alloys, polymers, hybrids, ceramics, and gels. Moisture-responsive materials react in contact with water or moisture and are widely preferred by researchers since water is widely available. The most common material is hydrogel since it react vigorously with water.

and are widely preferred by researchers since water is widely available. The most common material is hydrogel since it react vigorously with water. Photo/electro/magneto-responsive materials react with light, current, and magnetism. Many of them have photo-responsive chromophores infused with polymer gels at specific locations to swell when exposed to certain fields.

A 4D printed hook that folds to grab a screw when heated

It’s important to note that heat and moisture responses contain more major reactions as opposed to photo and electro responses, meaning they can be more easily understood and studied.

There are a ton of applications for this! For example, a self-repair piping system could be programmed to change in size in response to water pressure, minimizing the amount of pipes that burst. People could also customize and build small-scale 4D printed proteins and create devices that release medicine when the patient gets fewer minerals or their body starts to break down.

Other possible applications

But there’s largely untapped potential in one area in particular: space travel.

DANGERS OF SPACE TRAVEL

There’s a lot we don’t know about space travel and its effects on the human body over a three year time-frame and while we want to prioritize remote health checkups, there’s a twenty minute delay in radio signals from Mars to Earth and at least double that for verbal responses. That means that a doctor or healthcare professional would have to be on board with access to tons of different materials in case of emergencies.

Once we actually get to Mars, we need to consider cosmic ray protection, how to transform Mars’ atmosphere, and how a weaker gravity will affect our bodies. Rover missions found raw materials that could be used to construct communities, meaning we wouldn’t have to front-load the spacecraft with these materials, but we’d still have to find a way to build a settlement that isn’t subjected to the sun’s harsh radiation.

There are tons of other problems like lack of accessible water on the surface (mostly ice), lack of breathable air, extremely low water pressure, and freezing cold temperatures with an average of -85 degrees F (-65 C).

Space travel is also super expensive.

The cost of transporting just 1 lb of equipment into space is around $5–10 thousand dollars. NASA has been experimenting with inflatable habitats for the International Space Station and shape shifting rods but so far, it hasn’t created a large enough deficit.

In the aerospace industry, there are two main things they prioritize: fuel consumption and aircraft emissions. Improving performance lies with better altitude capability, lower noise, better cargo handling, improved systems response, and longer structural life. 3D printing has already been shown to be “high performance with excellent strength-to-weight ratios and has the ability to reduce inventory levels as well as costs of logistics for future prospects concerning spare parts”. Now we need to apply that to 4D printing.

While this study mostly focused on airplanes and airline travel, it mentions that “morphing” structures and using smart adaptive materials is one of the first steps in transforming the industry as a whole. In order to keep these two priorities in check, the spacecraft has to be light but still be able to withstand the harsh temperatures of launch and landing. Depending on the orientation of Earth and Mars, the trip could take 150–300 days depending on the speed of the launch. How much fuel are we willing to burn?

Model of satellite built with smart adaptive materials

When launching, a method called aerocapture is used to insert the spacecraft into orbit and achieve desired orbit in a single pass by entering the deep atmosphere. This requires a lot of fuel and has to be carried all the way until the spacecraft reaches its destination, in this case Mars. Historical studies have shown that it’s a fairly low-risk technology but they were based on smaller payloads for robotic missions.

This maneuver also creates more friction upon entry into Mars’ atmosphere, which would cause the vessel’s speed to be transferred into heat, requiring an extra shell and thermal protection system. This could potentially add more weight to the spacecraft.

Unless…

4D PRINTED CHAINMAIL: SPACECRAFT ARMOR

NASA may have a solution.

In the last few years, the Jet Propulsion Laboratory at NASA has been working on a metallic space fabric that has the ability to both reflect and absorb heat while protecting the desired surface. It’s a series of 4D-printed interlocking stainless steel squares with one side that reflects and one side that absorbs. They originally meant for it to act as a strong shield to protect astronauts from space temperatures and flying debris but they envision it to be multi-faceted.

“It could act like tire treads on the moon or as armor for astronauts and robots or even be used to deflect heat on more sensitive components like antennas,” says Raul Polit Casillas, a systems engineer at JPL.

They envision this kind of material being programmed to move electrons, transfer energy, and shape shift in the near future. There’s also a possibility of it being used to regulate water pressure within the human body. On Mars, water boils at human body temperature, meaning that without a suit to regulate it, humans would lose consciousness when exposed. Originally, we thought that we would have to have an airlock when traveling or living on Mars, but in the future, we could have a way to conceal our bodies and prevent things like prolonged cancer due to interplanetary and surface radiation using 4D printing!

There’s also a ton of other uses for this kind of 4D printing technology. Elon Musk plans to go to Mars in the next couple of years and with multiple astronauts all living together, the spacecraft is going to need a lot of space. That also means it’s going to be extremely heavy, over 40 tons on average. But that’s something we can take into account with these new advances.

Not only does this 4D printed armor offer us a new way of lightening the load by replacing a heavy external protectant, it can more efficiently transfer heat on reentry. Again, less weight = less fuel, which makes it more cost efficient to make the aircraft lighter and spend money on better fuel efficient techniques.

“It’s about believing in the future and thinking that the future will be better than the past. And I can’t think of anything more exciting than going out there and being among the stars.” -Elon Musk

It’s only a matter of time before the general public catches onto what 4D printing is capable of. It’s just the beginning! So whether you want to print a 3D figurine of your favorite Marvel super hero or build your own bioprinter to trace bacteria, there’s always room for more.

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