A fluid injection device for ejecting fluid droplets in response to electrical signals comprises an oscillating surface that has one or more tapered apertures, each aperture having a first and second opening. The first opening of each aperture is larger than the second opening. The first opening is in...http://www.google.es/patents/US7108197?utm_source=gb-gplus-sharePatente US7108197 - Droplet ejector with oscillating tapered aperture
