Very interesting that I saw this post this morning. I was actually reading something like this not that long ago.
Have you checked out these products, https://www.top5reviewed.com/digital-nail-printers/ ?
There might be a couple of products that Xerox offers that might suit your needs.
You need an offset printer with rollers and individual wet inks. Not really practical for your applications.
All laser printers print in dots. A "solid" red, when zoomed in, will show yellow dots interlaced with magenta. Zoom into any photo on any magazine and you will see dots of 4 colors only. As most modern Xerox print in 1200 dpi this isn't noticed.
All laser printers are required by law to print those yellow dots. The cones for detecting yellow do not exist in the human eye (only blue green red) so all colors other than primary must be infered. Those dots are not visible to the naked eye.
The only printers we have that print metalic are production presses.
All printers have a RML (Recomended media list). Depending what material/thickness/dimensions you want the decals to print on determine what printer can support that media.
I know most printers print in dots, and that is normal. However, I need a printer that prints SOLID colors, with no dots visible to the naked eye. I want to print water-slide decals and use for nail art. The colors on the decals need to be opaque and solid. What type of printer do I need to purchase that can do this for me? And, is there a printer that can also do metallic colors? If there is not one that can do both, I'm more interested in a SOLID color print. Thank you in advance.