"Dissolvable smartwatch makes for easier electronics recycling"
I didn't know that the disposal of smartwatches was a problem. I guess they've become so popular and cheap that they are now considered disposable. I would normally suggest that the technology is more appropriate for smartphone, but those already self-destruct if they are dropped, splashed with water, bent, overcharged, or repaired. Still, it would be a good way to provide hardware upgrades. Just wash away the old nano-particle PCB, and insert the new and improved replacement.
Of course, dissolvable nano-metals begs the question of how to dispose of the residual nano-debris and residue. I suspect that there might be something toxic in the mix. Of course, the same effect can be obtained with a large hammer or hydraulic press, but that's not suitable for publication. Athletic smartwatches might also be a problem. Sweat to much and the surface of the watch might look like sandpaper after 40 hrs exposure. Hopefully, the process is not cumulative or just about anything in a wet or humid environment will eventually self-destruct.
If the technology were scaled to something large like automobiles, it might be useful. Just park your car in the rain for 2 days and it disintegrates into a pile of nano-rubbish. Don't like the color of the paint? Just wash the car for 40 days and 40 nights, spray with primer, and it's ready for another color of removable nano-particle paint.
Progress blunders onward. Soon, everyone will be buying dissolving smartphones.