INSERTION PRINTS #3
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VIRUS (part 1)
 
     
  by Erik Es - Amsterdam, August 7, 2018  
     
  Whilst recovering from a bout of flu I decided to make a nice 3D
model of a virus. 

Viruses come in many different shapes. One type looks like a sort of
lunar lander. These are called "bacteriophages" (Greek: bacteria-
eaters). Like all viruses they are very very small. You need a very
strong electron-microscope to see them, and even those can just
about make them visible. They look like this:
 
   
  Check the scale in the left image: 100 nm is one tenth of a thousandth
of a millimeter... Keep in mind that these creatures are not organisms -
they have no heart, no nerves, no brain, no eyes, no ears, no bones,
nothing. Still, their behaviour is quite complex, which I find completely
baffling.

As you can see in the drawing, bacteriophages have a 6-sided lantern
shaped body. A thin hollow tube at the bottom ends in a "mouth" with
small "teeth". Around this mouth there are 6 very simple "legs" (but
remember: no bones, no muscles, no nerves...).

Inside the hollow body it carries small strands of DNA. As viruses have
no means of sexual reproduction, they have developed a completely
different and amazing system of procreation.

When the virus detects (?!) a living cell of the right type, it lands itself
on the cell's outer wall and attaches itself to it. It looks very much like a
lunar lander after touching down on the moon. After landing it bends its
"knees" until the "mouth" part touches the cell. The little teeth now drill
a small round hole in the wall of the cell, like a cookie-cutter shark. 

The virus then injects the strands of DNA into the cell. With its purpose
fulfilled, the virus now disintegrates. It doesn't actually "die", because
it was never really "alive" in the first place...

Inside the cell, the virus' DNA now inserts itself into the DNA of the
cell. By doing this it completely changes the behaviour of the cell.
Instead of performing its normal duties, the cell now turns into a virus
factory - it starts to produce new viruses, and lots of them...
These viruses then take off, looking for other cells to invade.
A very effective system.

There are over 1000000000000000000000 times more viruses than
there are humans on our planet. When you have a flu, there are trillions
of them in you alone... We are not aware of this because they are far
too small to be seen - or rather, WE are far too large to see one.


So I decided to make a printable 3D model of a bacteriophage, so
large that we CAN see one, but still small enough to fit on your hand.
However, the shape of the virus posed several major challenges...

I wanted the legs to be really thin, as close as possible to the original.
But with such thin legs it would be very hard to print the model in one
piece. The legs would be too thin to print nicely (unless I would make
the model VERY large...). Also, the "grain" of the print (caused by the
print layers) would cause the legs to be very weak. Too weak. 

So I decided to print the legs separetely, laying down flat. That way
they can be printed much nicer, and because the layers do not "cross"
the legs they are MUCH stronger - strong enough to hold the body,
even though they are very thin.

With the teeth of the virus now left as the bottom part of the body, the
model would be resting on these pointed teeth during printing - not a
good idea. It also seemed like I would have to make six holes around
the mouth to hold the legs, which would also cause problems with
structural integrity.

The solution I came up with was to make 3 pairs of legs instead of 6
single ones. Now all I needed was some slots at the bottom of the
base to connect the legs.

Perhaps you have seen (or even made) model animals like this :
 
   
  These come as kits, with all the parts cut out of a wooden plate.
The parts have small slots that allow them to be connected by just
sliding them onto each other.

As you can see, these parts are all connected under 90 degree
angles. I thought it would probably be possible to use this system,
but instead of 2 parts at 90 degrees, I needed to slot 3 parts together
at 60 degree angles.

Here you can see how I managed to do this:
 
   
  As you can see I also added the teeth to the legs. This way the teeth
can also be printed nice and sharp, and it leaves a much better base
for the rest of the model, with enough material touching the print bed to
hold the rest of the model firmly in place during printing (see the red
parts in the right image):
 
        
  With the body printed hollow, the model is suitable for "insertion
printing", so I can drop the strands of DNA inside the body just before
it starts to close up.

Now all I needed to do was figure out how to make the DNA... quite a
challenge. 

Read my next blog to see how I did this and see the end result:

DNA PRINTING - VIRUS (part 2)
 
 
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