Yesterday I made a number of images to try out different resolutions and drop distances, to see which work the best. One limitation is the size of the droplet that can be reliably dropped by the fab@home 3D printer. Another is that the arabinose dropped will dissipate through the agar, in effect creating a much larger pixel than the drop itself. Also, the bacteria can overdose on the arabinose, in the end not displaying anything.
I experimented with a simple X pattern, and also with some space invaders:
The initial resolution was 16×16 pixels, with various drop sizes. The drop sizes are defined by the amount of downwards movement that is made by the syringe tool, pushing the liquid out. The spacing between the drops can also be played with, and thus I did.
The three invaders below all have 5mm between the drops, and the drop sizes are also the same, 0.03. The difference is only in the amount of suckback after a drop is made – that is, some liquid is pushed out, and then there’s a backwards movement in the syringe, sucking excess material back. The invader on the left on both images has a suckback of 0.01, while the ones on the right have none and 0.015, respectively.
It seems that no suckback resulted in an overdose of arabinose (see that the silhouette of the invader is visible, but the inside is dark). It also seems that a suckback of 0.015 was too much, though this is unclear why.
I also experimented with 32×32 pixel resolution images, with shorter distances between the drops, and smaller drops still. Here, the drops really got together during printing (see yesterday’s post), thus the result is really just blog blobs, with arabinose overdose in the middle:
The invaders, from left to right, were made with the following settings:
- spacing 3, drop 0.02, suckback 0.01
- spacing 2, drop 0.015, suckback 0.01
- spacing 1.5, drop 0.005, suckback 0.002
The next experiments will involve more spacing and smaller drops, so as th prevent arabinose overdose, and also to enhance the effect of single pixels.
It’s also a challenge to make these photos, in low light conditions it’s very difficult to focus properly. Still, thanks to Dániel Molnár for his tripod, as my own is still missing