Curved screens on modern smartphones present a problem for screen protectors because it's hard to get the screen to lay flat. No matter what, it seems as though they eventually lift around the corners, catch on things, accumulate debris between the layers, and ultimately just come off.

A response to this has been UV screen protectors that adhere to the display using UV curing glue. The idea is you apply the glue to the display, fit the screen protector on top, align it to get a perfect fit, and then blast it with UV light to cure the glue and get the perfect screen protector fit.

Also: How to fix a cracked phone screen: 5 options

If the screen protector breaks, you're supposed to be able to use a hairdryer or hot air gun to soften the adhesive to get the old protector off before applying a new one. You can even buy kits to do this yourself,which cost about$30 and come with everything you need, even the UV curing light.

This is all theoretical, of course. Unfortunately, the reality is a little different. 

Air bubbles and dirt can get trapped in the adhesive, it can cause fingerprint readers to be unresponsive, the glue can cause skin and respiratory allergies