In this work, we investigate different printing technologies suitable for mass production of millimeter-wave antennas and other devices, e.g., holograms and frequency selective absorbers, on flexible substrates. We concentrate especially on roll-to-roll reverse offset printing. The driving factors are low cost, high accuracy, high efficiency, and reliable performance. Therefore, we need to find and characterize suitable flexible substrates (permittivity and loss tangent at mmwavelengths), conducting inks (viscosity, surface resistance of the resulting conducting layer), adhesion of the ink to the substrate, and feature size capable for printing mm-wave antennas and other passive devices in high volumes.

This paper presents the results from evaluation of suitable materials and ink properties for printing millimeter wave components. Dielectric parameters (relative permittivity and loss tangent) of various potential substrate materials are extracted from S-parameter measurements and simulations. Test samples are being printed over Polyethylene Terephthalate (PET) substrate and the measurement of their performance will be reported in the final paper.

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The Panchthar, a hilly district of Eastern Nepal, has several medicinal plants which are used by indegenous people for the treatments of different diseases. In the present work, phytochemical and biological activities of hexane, ethyl acetate, acetone, and methanol extracts of Litsea monopetala leaves from the Pachthar district were analyzed. The phytochemical screening demonstrated the presence of major secondary metabolites like flavonoids, alkaloids, terpenoids, polyphenols, glycosides, and proteins. The antibacterial activity was estimated by the disc diffusion method against Bacillus substilus and Escherichia coli. The result showed that ethyl acetate extract exhibit the highest zone of inhibition (ZOI) value of 18 mm/disc. Acetone extract also showed significant antibacterial activity at the concentration of 100 mg/mL. Antioxidant activity from DPPH radical scavenging assay displayed the inhibitory concentration (IC50) values of dried methanol and acetone extracts were 30.74 μg/mL and 202.86 μg/mL, respectively. The methanol extract has the highest total phenolic content of 360.14 mg GAE/g extract and the highest total flavonoid content of 27.13 mg QE/g extract. The present study revealed that Litsea monopetala plant from the Panchthar district is a source of several bioactive substances and can be used in several drugs formulation.