Electrospray methods and systems for coating of objects (e.g., medical devices such as a stent structure) with an open matrix coating. The open matrix coating is formed by electrospray using one or more nozzle structures each having at least an inner and outer opening. A first flow of a liquid spray composition is provided to the inner opening and a second flow of a liquid diluent composition is provided to the outer opening (e.g., the liquid diluent composition including at least one solvent, such as a composition having a dielectric constant equal to or greater than 10).