I've been thinking about alternatives to support materials for FDM printers, such as multi axis printers, dual head with soluble support material or printing in a gel/liquid which traps the material in place. Then it occurred to me that it might be possible to use the surface tension of a liquid to act as support material, same way small objects an insect can float on water even though they are heavier than water. This would also work great for cooling the extruded material. NOTE, we are still using a base plate like any other FDM printer, the only difference is that we have a water surface on the build plate which act as support material for large overhangs/steep angles. Everything is still attached to the build plate itself. We are not just printing stand alone parts on the surface of the water.
After some highly scientific testing (Dropping an extruded string of PLA and placing a thin printed PLA part on the top of water) I've concluded that it is very feasible to float PLA on the surface tension of water. See picture for refence:
As you can see the floating structure is not at all trivial, it has both smooth round shapes and many sharp corners and holes in it, it was still extremely simple to get floating (I could drop it in from a height of 5 cm and it would still not break the surface tension). I also tried my best to investigate the effects of having structures underneath which might mess up the surface tension by placing larger PLA parts under the floating ring and trying to sink the ring by touching the underside and corners without any success at sinking the floating part. The only way I could get this part to sink was to push it down under water. Even if the surface tension was only broken half way along the ring the ring would still float. If you are thinking that the ring acted as a boat, that is not the case. I made sure to fill the small indents with water so that there were no pockets of air keeping it afloat.
An even more encouraging result was another ring which was much thicker than it was wide. It still managed to float from the surface tension on the top side of the structure while the rest of it was submerged, accurately mimicking how the structure would actually be in the water during printing. See picture:
While this ring much easier to sink it was very resistant to being moved around. Again, basically the only way to sink it was to push it down under water, though as soon as the surface tension was broken on one side the whole ring quickly sank.
All this leads me to my question: Does anyone know of a 3D printer which uses the surface tension of water as support material?
I've searched around some on the web and I have not really found anything at all on the matter. I can foresee many potential problems (such as the extruder moving unsupported lines to the side when changing direction, layer adhesion, enclosed areas not filling with water etc) but the potential to print without support and only have to worry about keeping the newly extruded material in place could open up a lot of potential.
UPDATE: I also tried 60 degree Celsius water (In case you need hot water to help with layer adhesion) and the surface tension still was able to float the thicker ring piece, though it felt like the surface tension was weaker.