The work volume contains a gas, at least part of which can be condensed to a solid by cooling. It may be regular air with a little humidity, below freezing point, or it may be a custom gas.

A laser of slightly below the resonant frequency of some of the gas particles is focused where you want material deposited. For molecules moving towards the laser it is Doppler-shifted to resonant frequency and hits the molecules, slowing them down. For molecules moving away from the laser it is Doppler-shifted away from the resonant frequency and doesn't hit the molecules.

It cools enough in that location that the condensable part of the gas becomes solid and is deposited as intended.

The laser scans around to created the rest of the object.
-- caspian, Aug 31 2011

Laser cooling http://en.wikipedia.../wiki/Laser_cooling
For more information [Vernon, Aug 31 2011]

Animation of the laser Maxwell's demon gate http://www.scientif...eriment-interactive
[sqeaketh the wheel, Aug 31 2011]

Isn't Laser's significant in that they produce heat ?

A similar 3d build up of condaste of liquids turned to solid material, is used in regular 'SLR' tech - (stereo litrophi resonance or so,), by pointing focus points into a bath of a raising layers of fixed material.
-- sirau, Aug 31 2011


While there IS a known "laser cooling" phenomenon that is exploited by researchers seeking ultra-cold atoms, I'm not sure that the mechanism described in the main text here is the same mechanism that those researchers use. I'm reasonably sure that just because a photon might not equal the resonant-frequency needed to be absorbed by a particle, in the spectrographic sense, that doesn't mean the photon can't interact with the particle some other way, such as by "scattering" --and if enough photons bounce off a particle, that particle may be heated, not cooled.
-- Vernon, Aug 31 2011


There's an awesome article in one of the latest Scientific American's about using lasers to make a literal version of a Maxwell's demon gate trapping atoms one one side swapping entropy for information and release to cool things down close to absolute zero.

Sorta related. Cool idea [caspian].
-- 2 fries shy of a happy meal, Aug 31 2011


Yep, see link.
-- sqeaketh the wheel, Aug 31 2011


Could you mix different gasses, and adjust the laser to switch gasses at will, in order to make something out of multiple materials? I want one in my garage.
-- DIYMatt, Sep 01 2011


Thanks for the link Vernon. Doppler cooling on that page is what I was thinking of. Looks like it works better for atoms than molecules, and there's some more conditions I wasn't aware of, so maybe some atoms aren't so selective about photon frequency, and probably molecules aren't, but otherwise I think my description matches.

DIYMatt, good idea. I hadn't decided whether the directly cooled particles had to be the ones deposited, or if other particles would get indirectly cooled and deposited, but if cooling different atoms will deposit them in particular there are several laser options. I gather there are tunable lasers. And also you can just have a second laser.

sqeaketh, 2 fries, good link.
-- caspian, Sep 01 2011


What prevents the ink from boiling off the substrate again after the laser leaves it? Maybe the ink reacts chemically with either the substrate, or another ink component, but only in the liquid phase?
-- mouseposture, Sep 01 2011



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