h a l f b a k e r yQuis custodiet the custard?
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XRay Computed tomography, kinda backwards, and without xrays.
Start with a 3D model you'd like to print. Have the computer compute shine-through projections of the object from, say, a thousand points on a circle around the object.
Next: Buy a cylindrical aquarium, LCD screen, grow-lights, algae-spores,
a model train and some gelling agent.
The LCD is mounted on the train, circling the aquarium, with the grow-light (point-light source) attached to the LCD, at the distance the projections were computed for. The LCD shows the projections at the locations on the circle they were computed for. Thus, every point in the aquarium (which has been filled with algae spores dispersed in gelled water) receives more or less light, differentially stimulating the growth of the algae.
Some days of circling will create an algae representation of the 3D object.
Might work with UV curing resin , a static light source and a turning cylinder too, but wouldn't be so cool.
EDIT: with different cyanobacteria color printing might be possible
CT basics
http://www.phoenix-...on/tomography_e.jpg
LCD would be between source and sample, showing inverted pic visible on the array detector [loonquawl, Jan 16 2009]
Photosystem II - Wavelength dependencies
http://upload.wikim...s/c/c7/Z-scheme.png
For the advanced version with two intersecting beams [loonquawl, Jan 16 2009]
[link]
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I like this idea a lot, especially the part with the train, but I don't understand how it would produce algae in the middle of the cylinder; I would have thought it would just make an essentially 2-D pattern* on the inside of the aquarium glass, unless there's some way that a rectilinear beam of light can bypass the peripheral spores and promote the growth of the deeper spores. |
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*or perhaps a rather limited set of spoke-like 3-D patterns, where each green point is extended into a green line from one side of the tank to the other |
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At first, the aquarium will be pretty translucent, almost clear, so the light will shine right through, as the xray does in CT. Only later will the developing cytochromes (or chlorophyll) attenuate the light in any great degree (-the computing of the projection might have to be adapted to measured or guesstimated absorption) At that point, scattering becomes a problem too. This might be mitigated by the use of two light sources with complementary wavelenghts, exploiting the intricacies of photosynthesis.
Uv cured resin would not suffer by this. |
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//two light sources with complementary wavelenghts// Ah! So, you produce photosynthesis only at a point, not along a line, by making it only occur where two (perpendicular?) waves interfere? |
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So you'll need two very punctual trains.[+] |
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the script generating the punctual trains will be sold to railway companies generating huge profit... |
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Or the second Lightsource+LCD is on the same train, 90° along the rail.... |
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//the intricacies of photosynthesis// |
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<suspiciously>Could you provide an explanatory link?</suspiciously> |
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