Acoustic ink printing

An acoustic beam focused on a free liquid surface is used to eject discrete ink droplets of controlled diameter. The liquid surface, adjusted to be at the focal plane of a suitable focusing element, is excited with a burst of acoustic energy. Spherical lead zirconate titanate (PZT) shells, acoustic microscope lenses, spherical lenses etched in silicon, and Fresnel acoustic lenses are used successfully to eject droplets. Droplet diameter scales directly with the focal spot size, and inversely with the acoustic frequency. Droplet formation is experimentally demonstrated over the frequency range of 5 to 300 MHz, with corresponding droplet diameters from 300 to 5 mu m. This droplet ejection process is successfully utilized for a printing application by using ink as the liquid medium. Acoustic ink printing with a single lens and with an array of lenses is described.<
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