Abstract: Disclosed are sets of ink components, and ink compositions, useful for printing markings, on security documents, that are relatively resistant to counterfeiting. Also disclosed are the security documents formed, a method of printing and a method of authenticating the printed material. The markings, formed of the ink compositions have a spectral response that deviates from a predicted spectral response when linearly additively combining spectral responses of components of the ink composition, so that it becomes difficult to reverse-engineer the ink composition from the markings. Use of plural different markings, with each marking being a microdot, increases difficulty in counterfeiting. By forming a template of spectral responses of the original pattern, spectral responses of a pattern on an unknown document can be compared to the spectral responses on the template for determining whether the unknown document is authentic. Formation of the markings is facilitated using an inkjet printer.

Abstract: Amplitudes of drive pulses received by a horizontally-placed dropper determine the horizontal displacements of droplets relative to an ejection aperture of the dropper. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal interdroplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications.

Abstract: A droplet generator comprises a fluid reservoir having a side wall made of glass or quartz, and an end cap made from a silicon plate. The end cap contains a micromachined aperture through which the fluid is ejected. The side wall is thermally fused to the end cap, and no adhesive is necessary. This means that the fluid only comes into contact with the side wall and the end cap, both of which are chemically inert. Amplitudes of drive pulses received by reservoir determine the horizontal displacements of droplets relative to the ejection aperture. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal interdroplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications.