How to build a person. 4 – Feed!

Science Burrito and build-a-body return after a short hiatus. Previously, we saw that for our cells to produce the energy they need to work and, in turn, for us to live, we need oxygen to burn sugar. There’s another we can look at that though. We need sugar for that oxygen to burn! Our obvious next step then, is to get our mechanical man to feed itself. We already have bones, so teeth are covered (Kevlar teeth!). But we need to digest!


Feeding isn’t just about sugar kids. We need it, certainly. Not too much, of course, but some. If anyone tells you they’ve cut out literally all sugar from their diet, they are lying, or you need to make sure they’ve written you into their will. But you need a lot of other things too. Vitamins, minerals and the like. These other things build your cells, but the sugar is what fuels it.

This makes the digestive system very complicated, because it needs to be able to break down and process all different types of foods, but also it needs to keep us safe from poisons.

Now, we could handle the digestive system one bit at a time. We could look at the stomach, which is filled with hydrochloric acid. So we need a bag to hold acid. That’s not too hard though. Stomach acid can’t be too strong, or it would dissolve our bodies, so a simple rubber bag, maybe coated on the inside with some acid resistant plastic like PTFE.


We could talk about the kidneys, which, along with the liver, filter toxins out of the blood. But dialysis machines already exist. They are very large machines, so not perfect for our body, but they’re pretty cool. They work thanks to our old friend, the semi-permeable membrane. Blood passes through tubes made of this membrane and toxins filter out of the blood and into a fluid that surrounds the tube. Pretty simple, pretty easy, but very big.


We could talk about the intestines. The walls of the intestines are also semipermeable, and nutrients flow into the blood through these walls. They are covered in tiny, tiny hair like bobbles that are just 1 tenth of a millimetre wide, called villi. These give the intestines an absolutely huge surface area. And with our metal human already a “3 times the usual size” giant, it shouldn’t be beyond our capabilities to make them. If we can work out how to make the materials, we could even 3D print it!


Most of the rest, we could talk about, but as you can live without a gall bladder, a spleen and your appendix, we might as well not worry too much about them right now. Our android is going to be hard enough to build, so let’s not over complicate it.

In fact, come to think of it, why make it all so difficult in the first place. This is our robot, we can make it however we want to. And as it will be made of plastic and Kevlar and metal, rather than cells, we don’t need all the vitamins and minerals and stuff, just the fuel to keep it running. So let’s replace all of the complicated stuff with one stomach, lined with a semi-permeable membrane which some blood vessels run over. And let’s have the robot only drink sugar water, because that’s all it’ll need. We could even add a little sensor that only lets the water out of the stomach when most of the sugar is gone.

So there it is. A bit of a cheat on this one, I’ll admit, but you can see how we might make the whole digestive system (at least the important bits) if we had to.

Next time, we’ll see just how our robot is going to convert all this sugar and oxygen into power.

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