Patent ID: 7316067

Claim:
A method of forming a perforate membrane for use in a liquid transport device, by applying laser energy selectively to a first surface of the membrane in the form of a pulsed, focused beam to form a plurality of nozzles each having a throat portion opening of a selected diameter at one end through the opposite surface of the perforate membrane and a smoothly curved outwardly diverging portion extending from the other end of the throat portion to the first surface of the perforate membrane, and further comprising the steps of: thereafter electro-polishing the first surface of the membrane and the surface of the diverging portion of the nozzles to remove surface imperfections, and controlling the electro-polishing so as to remove material from the surface of the diverging portion of the nozzles to a depth within the membrane less than the length of the throat portion so that the diameter of the throat portion is unchanged by the electro-polishing step.