A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, most commonly ultraviolet light. Usually, it is used in 3d printing, especially to achieve the effect of embossing. These resins can have varying degrees of flexibility, hardness, or transparency. However, some resins can be brittle.  

Currently, scientists experiment with sustainable alternatives. However, no alternative have been fully adapted for commercial use yet.