An apparatus and method for coating abluminal surface of a stent is described. The apparatus includes a stent support, a coating device, and an imaging system. The coating device includes a solution reservoir and transducer assembly. The transducer assembly includes a plurality of transducers and a controller. Each transducer is used to generate focused acoustic waves in the coating substance in the reservoir. A controller is communicated to an image system to enable the transducers to generate droplets on demand and at the predetermined ejection points on the surface of the coating substance to coat the stent. A method for coating a stent includes stent mounting, stent movement, and droplet excitation.