Exposure of a positive resist to radiation changes the chemical structure such that it becomes a liquid or more soluble. These changes in chemical structure are often rooted in the cleavage of specific linkers in the polymer. Once irradiated, the "decomposed" polymers can be washed away using a developer solvent leaving behind the polymer that was not exposed to light. This type of technology allows the production of very fine stencils for applications such as microelectronics.  In order to have these types of qualities, positive resists utilize polymers with labile linkers in their back bone that can be cleaved upon irradiation, or use a photo-generated acid to hydrolyze bonds in the polymer. A polymer that decomposes upon irradiation to a liquid or more soluble product is referred to as a positive tone resist. Common functional groups that can be hydrolyzed by a photo-generated acid catalyst include polycarbonates and polyesters.