Creating and harvesting surface-bound emulsion

A method of making an emulsion, comprising:

• (a) obtaining an array of polymeric compounds on the surface of a substrate, wherein the polymeric compounds are bound to the substrate via a cleavable linker and wherein the areas that contain said polymeric compounds on the surface of the substrate are hydrophilic relative to the remainder of the surface of the substrate;
• (b) selectively hydrating the areas that contain said polymeric compounds by flooding the substrate with an aqueous reagent and then removing the aqueous reagent from the substrate to leave discrete droplets of the aqueous reagent on the areas that contain said polymeric compounds, wherein each droplet contains a single polymeric compound or a pre-defined combination of polymeric compounds that are adjacent to one another on the substrate;
• (c) releasing the polymeric compounds from the surface of the substrate by cleaving the cleavable linker, either before, during or after the hydrating step (b);
• (d) collecting the droplets in an immiscible liquid, thereby producing an emulsion containing discrete droplets, each of which containing, in the solution phase, a single polymeric compound or a combination of polymeric compounds that are adjacent to one another on the substrate.