Additive Manufacturing – Making Existence Question

‘Are you friggin’ kidding me?’

This was the usual response of friends and teachers to one of the main ideas I was considering for my thesis. And I cannot blame them either, because the concern was legit – shit was involved, literally. After many discussions, I finally told myself that additive manufacturing with human feces would be a project I must save for another lifetime. In retrospection though, I too agree that it would have been a bit too much – I saw myself, a year from then, clutching at whatever little that remains of my hair staring at a brutally hacked filament extruder which was either: a. unable to extrude the material (aka constipation) OR b. extruding it at undesirable rates (aka diarrhea). Either one of that happening, and that too at a graduate thesis exhibition show in a crowded art gallery, would make it the perfect disaster.

‘Dude, as if shitting on the streets for you guys (Indians) was not enough..’

Though the highly sanitized modern societies manage to project the image of the penultimate pristine very well by pushing the excrement under the rug (or the streets), the problem is not really gone and it re-surfaces every now and then in every corner of the world (usually happens when it rains a lot). The attitudes towards management and handling waste vary but all in all, it is looked at as a thing that must be immediately gotten rid of. The truth is, all of our civilization and us are covered in filth – of our own excretions and those of others. Come to think of it, societies are the best way to come into direct and indirect contact with the excrement of others. What was once limited to probably the animals and the family on the farm now extends to everyone who sat on that toilet seat or touched the door knob of that high-society lounge you and I might wish to visit. With that at their core, societies strive for ‘cleanliness’. Over hundreds of years, we have solved certain problems and introduced practices that positively transformed health and hygiene at a global level, but with that attitude we are also flushing the baby out with the bathwater.

Building Material Of The Future – Here and Beyond

Used as a fertilizer, fuel and a construction material regardless of time and place – it is only sensible to see it as the next big problem as well as the answer to the mounting pile of humans and their excreta. A few efforts have briefly brought some attention to the potential of feces as a construction material but the stigma is an understandably great one to overcome. This also prevents further work towards solutions that will help, and the reactions I experienced, ranging from understandingly disagreeing to extreme mockery, were a good example of that. The common concern of biological hazard and odors has been addressed long ago and the only thing that requires work is our perception. Think of it – an abundantly available ecologically friendly material that can and has been used to create strong composites!

As we are expanding our reaches into the space, talks about colonizing Mars are getting serious with every passing day. Dealing with humans and their waste will thus be more important than ever. Since energy efficiency is of utmost importance in space missions, researchers are exploring ways to fully utilize this space poop (as an energy source), which would otherwise be stored and hauled back to earth. They have been doing that with urine and astronauts already get enough questions on that. Also, no matter how tempting it sounds, we cannot just let packets of frozen human feces drift for a millennia until they land on a planet wiping out an alien life (or even birthing it). So, the solution will be simple for us – we will have to figure out a way to use our own feces to construct these new worlds. And when it is 3D printed (ie. if my hypothetical extruder works by then in Mars’ gravity, I am also fine with throwing lasers at sewage sludge blended with a photo-polymer if that looks cooler) and setup by an army of robots, the possibilities can be endless. All humans would need to do would be to wake up from their deep sleep upon their arrival and move into their new Martian homes made out of waste collected from the previous missions. As they live, they shall also contribute their bit for the future occupants of that community. Will be just like the stories where the filth off one’s body was used to create heroes and their armor.

With access to FDM 3D printers for a class I was the teaching assistant for, I started with a few quick projects of my own to learn more about this technology. The opportunity couldn’t have come at a better time as I was also taking an engineering course on 3D printing, so there were lots of ideas that I wanted to try.

Nature uses many methods to create which could be classified, in human context, into three types – Additive, subtractive and transformative. All of these are also used in varying degrees by humans, themselves a part of nature, to create new things – we have mostly been using subtractive and transformative methods (like turning a tree log into a chair and making bread and iron) for a very long time in manufacturing; but additive manufacturing is relatively, at least as what it means now, a new process. We have borrowed a lot of ideas from nature in our subtractive processes and have pretty much augmented nature for our transformative processes. Thus, driving the additive methods back to how nature uses them only makes sense.

So, I wanted to 3D print an egg – something absolutely unnecessary, yes. But there is much more to an egg than there is to the generic nuts and bolts or pikachus that get printed as test pieces all the time. Through additive manufacturing, I wanted to study and imitate this structure as it is created in nature, ie. without internal or external supports.

The ovoid is an interesting shape and its properties of strength and stability also make it the subject of many studies and applications. While reading up about eggs (do not ask why), I got to know more about how evolution, local resources and thermodynamics play a key role in determining their shape. The way by which an egg is created within the bird is an interesting process by itself, the tube of the oviduct creates and shapes its shell it as it passes through – an additive process which we might try to replicate in the future as an assembly line which is way more compact and efficient.

Using the thinnest wall thickness possible, I first printed a chicken egg (closest to an ovoid) in PLA which came out just fine, but the slicer put an internal singular support column running through its central axis. I had missed out on enforcing the no support setting so the entire curvature was unsupported except for the top and the bottom. Even with that, it turned out to be super strong and one could throw it at the floor with as much force as possible and the thing would just randomly bounce off in another direction. Interesting.

Next, I printed the same egg but with a meshed or a voronated surface. Voronoi partitioning of a surface finds use in modelling bone architecture, cells, scaffoldings for growing specimens; and it also simply looks cool. This is also probably the closest one can get to generative design like forms without actually using a generative algorithm. These very alien looking eggs took a longer time to print, even with lesser material, because of the discontinuity in deposition and the very gradual and varying slopes which bound each voronoi curve. This too printed without much problems, except for one, which was by my own lack of patience. It printed with a base to which it was attached, I hastily pulled the whole piece without judging its sensitivity and it broke at the bottom. This structure, also printed at minimum wall thickness, was actually very interesting – it flexed and yielded like a sponge but maintained its original geometry. This spongy egg, did manage to give me ideas for another class project I was working on (scaffolding for silicone prostheses).

Now that I was successfully able to 3D print eggs without any (or at least minimal) structural support, both with the solid shell and a voronated one, I can safely say that the this natural shape also accommodates for the slope angles within which a man-made filament extruder works. I am now thinking how this idea would hold if I print these with the stereolithographic process – ie. how does the surface tension of the photopolymer and the vaccuum that it might create for this egg shell affect the results. I feel it might work, but I have to test that.

Some interesting info on eggs:
http://science.sciencemag.org/content/356/6344/1249http://vis.sciencemag.org/eggs/

Click to access egg.pdf

https://web.stanford.edu/group/stanfordbirds/text/essays/Eggs.html
https://news.nationalgeographic.com/2017/06/bird-eggs-shapes-flight-evolution/

Tag: Additive Manufacturing

Printing That Shit

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