I've gotten a couple gel manicures recently, it's addicting once you start because it lasts a long time. I'm taking a break from it because it makes your nails brittle. They make special gloves you can wear that just expose your nails, ideally I was thinking the same technology in 3d projection mapping could be used to only expose the nailbed to uv ligt with hand tracking. It would increase the the cost of one of these uv curing devices by smartifying it but would prevent cancer...
Flipping through <a href="https://www.google.com/search?q=photoinitiator+absorption+spectrum&tbm=isch" rel="nofollow">https://www.google.com/search?q=photoinitiator+absorption+sp...</a> suggests that some photoinitiators work with 222nm UVC light.<p>That wavelength is currently undergoing safety testing for killing germs. Maybe that's a possible alternative? Penetration depth might be an issue, since that's what (supposedly) makes it safe for skin.
> …on the genomes of primary mouse embryonic fibroblasts, human foreskin fibroblasts, and human epidermal keratinocytes.<p>don’t put your… you know what, never mind, too late.