Highly-filled polymer systems include color masterbatches, feedstocks for powder injection molding, and rigid sheets with high levels of flame retardants, but they have not been explored for flexible sheet. This work investigated the (a) selecting a polymer matrix with enough melt strength and flexibility to form a stable sheet with high filler loading, (b) the maximum achievable filler loading for the sheet, and (c) optimizing the process of extruding a highly-filled flexible polymer system. Extrusion grade low-density polyethylene (LDPE) provided sufficient flexibility and permitted a maximum filler loading of 36 vol% (~78 wt%). Good dispersion of the nanoparticle filler, however, required two passes through multiple screw extruders and a small reduction in the viscosity of the LDPE. Sheet with thickness of 415 μm, surface roughness of <1 μm, and sufficient flexibility was extruded continuously at a rate of 10 m/min., but it required a more traditional coat hanger manifold to prevent filler hang up in the sheet die. The filler particles were distributed uniformly through the core and skin of the sheet, giving the sheet good mechanical properties.

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This article presents a printed tunable right/left-handed leaky wave antenna (LWA) on a new flexible, tunable low density polyethylene-barium strontium titanate composite substrate using an aerosol jet printer. The new substrate had a dielectric constant of 16 and tunability of 3.5% at f = 10 GHz. Interdigital capacitors (IDC) were utilized in the leaky wave antenna design not only to act as shunt capacitor in CRLH transmission line design but also as tunability element to implement tuning capability of the LDPE-BST substrate for antenna beam steerability for a fixed operated frequency in X-band frequency range. Up to 15 beam steering was achieved by applying DC voltage through the printed leaky wave antenna.

Stretchable electronics are being used in applications such as wearable electronics, robotic skin, wearable health-monitoring devices, and smart textiles due to their excellent mechanical conformability through stretching, flexing, twisting, and folding. This work focuses on creating printable stretchable substrates based on butyl rubber (IIR), combined with a ferroelectric filler, barium strontium titanate (BST). BST has unique properties, including the ability to tune the dielectric properties by applying a bias to the substrate. A high loading of BST was incorporated to tailor the dielectric properties of the substrate. This work investigated the effect of three different cure systems on the properties, including interaction with a silver ink. For all cure systems, cure and scorch time decreased with increases in BST loading. A phenolic cure did not affect the ink conductivity, whereas the sulfur-cured systems resulted in nonconductive ink. For the phenolic-cured substrate, the tensile strength increased and the elongation decreased with increasing filler loading. The elastomer could be filled with up to 40 vol. % BST while still maintaining elongation greater than 200%.

Slow flow diffusion cooled CO2 lasers mostly use dc electrical discharge for excitation. Preionization in the discharge tubes of such a laser helps to initiate and maintain the dc discharge at voltages below breakdown voltage. A high frequency pulser using an insulated gate bipolar transistor as switching device is developed for preionization of the 20 discharge tubes of the 1 kW multibeam CO2 laser that we have developed. This pulser produces positive pulses of 10 kV peak voltages; frequency variable from 1 to 5 kHz and its pulse width is variable from 1 to 10 μs. The rise time of the pulses is between 600 and 700 ns. Preionization allows dc discharge excitation simultaneously in all discharge tubes of the multibeam CO2 laser even at high operating pressures. Other advantages of the preionization technique, such as the discharge stability at lower discharge currents with lower ballast resistance and the shorter inactive zone in the discharge tubes, are discussed. This pulser can also be used with dc excited fast axial flow CO2 lasers and other discharge devices.