US Patent 7108354 Electrostatic actuator with segmented electrode

An electrostatic actuator includes a segmented flexible membrane associated with individually addressable electrodes, one for each membrane segment. The electrodes are provided beneath a corresponding one of the membrane segments to define a plurality of actuator chambers between each of the electrodes and the corresponding membrane segment. Control electronics independently provide a bias voltage to select ones or all of the electrodes to generate an electrostatic field between any bias electrode and the corresponding membrane segment to attract the corresponding membrane segment toward the respective electrode. Upon elimination of the bias voltage, the corresponding membrane segments are elastically restored to their previous position. This structure can be incorporated into a fluid drop ejector to achieve variable drop size by control of the number of segments actuated. Additionally, by control of the time and space domain of the segment firing, the pressure pulse created by the fluid drop ejector can be precisely controlled.