[bri3d]

They're doing the "growing" on a membrane at the bottom of the tank, instead of layer by layer at the top of the tank.

That should let them print really quickly and precisely, even compared to the SLA printers you link.

The reason it hasn't been possible in the past is that the polymerization process requires oxygen, which has only previously been available from the air over the liquid resin. Their system has some "secret sauce" for getting it to the bottom of the vat.

[8dad6bea]

You've got it backwards about the role of oxygen--it is being used to inhibit polymerization in this case. They are allowing oxygen to dissolve into a thin layer at the bottom of the vat so that the build doesn't stick to the membrane, and they can have a continuous draw.

The true build layer is actually within the liquid, near the bottom, but not on it.

[bri3d]

You're totally right. Oxygen inhibits the polymerization process. Interestingly, oxygen inhibition is also what allows things to be printed in layers (or, in this case continuously) as it allows the newly cured material to bond to the partially-cured inhibited material below it.