Two methods of direct-write printing for producing highly resolved features of a polymer impregnated with luminescent upconversion phosphors for security applications are presented. The printed polymer structures range in shape from features to text. The thin polymer features were deposited by direct-write printing of atomized material as well as by screen-printing techniques. These films contain highly luminescent lanthanide-doped, rare-earth nanocrystals, β-NaYF₄:3%Er, 17%Yb, which are capped with oleic acid. This capping agent allows the nanocrystals to disperse throughout the films for full detailing of printed features. Upconversion of deposited features was obtained using a 980 nm wavelength laser with emission of upconverted light in the visible region at both 540 and 660 nm. Features were deposited onto high bond paper, Kapton®, and glass to demonstrate possible covert and forensic security printing applications, as they are printed in various features and invisible to 'naked-eye' viewing at low concentrations of nanocrystals.

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In this work, lanthanide-doped, sodium yttrium fluoride nanocrystals were prepared and dispersed in a solvent consisting of 90 vol% toluene and 10 vol% methyl benzoate. Poly (methyl methacrylate) polymer was dissolved in the solvent, in addition to the nanocrystals. Inks were printed using direct-write techniques. Substrates used included Kapton®, bond paper, metal and glass. Stencil patterns and QR codes were printed with these inks. An overview of direct write printing for security applications is given. On many substrates, these printed traces are difficult to detect in ambient lighting, but can be easily read using near-infrared (NIR) illumination, making them very useful for covert and semi-covert security printing applications.

In this paper, ultra-wideband RF/Microwave components fabricated using a low-cost aerosol-jet printing technology are demonstrated on a 50 µm thick Kapton film. The demonstrated RF/Microwave components include a fourstage Wilkinson power divider and a novel planar quad Archimedean spiral true-time delay line. The printed power divider has achieved a bandwidth of 2 to 20 GHz with typical 2 dB insertion loss, greater than 25 dB return loss, and better than 25 dB isolation performance across the majority of the band. The printed delay line has demonstrated 2 ns true time delay with excellent delay flatness across the entire band. The performances of the printed RF/Microwave components are comparable to those of semiconductor based monolithic microwave integrated circuits (MMIC). Index Terms -Ultra-wideband RF/Microwave components, aerosol-jet printing, delay lines, power splitter.978-1-4799-5507-7/15/$31.00 © 2015 IEEE RWS 2015 200 μm pitch GSG Probe Pads Quad Archimedean Spiral TTD 50 μm thickness Kapton Substrate Delay (ns)