Sunday, November 02, 2025
UV Nail Gel Top Coat - A Solid Object, More Data
Using OXX Cosmetics UV Gel Top Coat (acrylates copolymer, hydroxypropyl methacrylate, hydroxycyclohexyl phenyl ketone) I wiped off the applicator brush on the brim of the container and touched the slide. With Probe One I printed what I'm starting to think of as the "Test Loop." I printed a few other bits and pieces, interlocking 80μm and 30 μm test squares, blobs etc., and cured the whole thing. First for 30 seconds with the built-in LED, then for 200 seconds on a 4W UV LED lamp. No significant shrinkage was observed.
The Test Loop consists of a nominal 100μm diameter circle with a 100μm line sticking out of the side. That's pretty much what I got. Note that this was done with two perimeters and 5μm intervals between dots. I could easily get 30 dots between dipping Probe One in the reservoir.
Under the trinocular microscope at 100x I tried to lift some test pieces of print with a hypodermic needle tip. They were not wet, but they did not stay together when poked. They were stuck flat to the glass slide. Fragments attempted to straighten out, so they were not in gel form. I had been printing for over 3 hours at this point, so the Top Coat definitely cures after prolonged exposure.
I went to the (now hardened) reservoir blob and pried the edge of that up. The thin edges tore, so I started prying at it until I found a piece that could be considered strong enough to peel away from the glass slide in a sheet. The material was quite flexible and could be bent over on itself. It returned to its original shape quite positively if slowly when released.
I propped up a torn segment on a 0.7mm diameter pin to get a look at the thickness:
The minimal durable film thickness appears to be approximately 30μm. I tried to determine the thickness of the printed Test Loop. Fragments edge-on were beyond the resolution of my optics. This would put the printed layer at very roughly 10μm or less.
Slicing Problems
While the probe dipping code works, and the PrusaSlicer integration is fine, the slicer doesn't accept layer and line thickness proportions that can be used on a scale of 1mm = 1 micron. I'm going to have to add some scaling to do layers, or use the PNG to GCODE script to stack my own. Possibly both. Also having to specify the reservoir location in the script each time I slice is a pain in the butt. May need to change the reservoir location to something closer to XY=(0,0).
Conclusions
UV Nail Gel Top Coat is a viable material for resin printing tests in air, though repeatable layering is yet to be accomplished.
With UV resin there seems little point in trying to print details much finer than 40μm at this stage as they are not robust enough to survive being detached from the glass slide with the equipment I have.
With 30μm voxels, it would take approximately 1mm^2 to make a complementary flexure that could move +/- 40μm. That would take several hours to print each layer at current speed, though that could be improved as micron precision is not required.
Probe One is a little too coarse for optimal resolution given 30μm voxels.
Given a maximal thickness of the printed layer of 10μm and a minimal viable mechanical thickness, any printed object needs to be at least 3-4 layers thick to survive manipulation.
