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Abstract-In this paper, the design and measurement of a 3D-printed low-loss asymptotically single-mode hollow-core terahertz Bragg fiber is reported, operating across the frequency range from 0.246 to 0.276 THz. The HE11 mode is employed as it is the lowest loss propagating mode, with the electromagnetic field concentrated within the air core as a result of the photonic crystal bandgap behavior. The HE11 mode also has large loss discrimination compared to its main competing HE12 mode. This results in asymptotically single-mode operation of the Bragg fiber, which is verified by extensive simulations based on the actual fabricated Bragg fiber dimensions and measured material parameters. The measured average propagation loss of the Bragg fiber is lower than 5 dB/m over the frequency range from 0.246 to 0.276 THz, which is, to the best of our knowledge, the lowest loss asymptotically single-mode all-dielectric microstructured fiber yet reported in this frequency range, with a minimum loss of 3 dB/m at 0.265 THz.Index Terms-Bragg fiber, electromagnetic propagation, millimeter wave technology, photonic crystals, three-dimensional printing.

In this paper, resin-based photocurable polymer materials for stereolithography, digitallight-processing (DLP), and polymer-jetting additive manufacturing techniques were characterized from 0.2 to 1.4 terahertz (THz) for their comprehensive dielectric properties, e.g., refractive index, absorption coefficient, dielectric constant, and loss tangent, by using laser-based THz time-domain spectroscopy. A total of 14 photocurable 3D-printing polymers were chosen, owing to their suitability, in terms of printing resolution, material characteristics, and so on, for millimeter-wave (mm-wave) and THz applications. The measurement results from 0.2 to 1.4THz, the dielectric constants of all photopolymer samples under test are between 2.00-3.10, while the loss tangents are from 0.008 to 0.102, which are quite useful for many applications, e.g., 3D printed antennas and THz transmission lines, which were demonstrated by an asymptotically quasi-single-mode Bragg fiber microfabricated by DLP micromanufacturing technique using HTM140-V2 photopolymer, which is previously reported at the nominal frequencies from 0.246 to 0.276 THz.

Abstract-A novel microfluidic-integrated microwave sensor with potential application in microliter-volume biological/biomedical liquid sample characterization and quantification is presented in this paper. The sensor is designed based on the resonance method, providing the best sensing accuracy, and implemented by using a substrate-integratedwaveguide (SIW) structure combining with a rectangular slot antenna operating at 10 GHz. The device can perform accurate characterization of various liquid materials from very low to high loss, demonstrated by measurement of deionized (DI) water and methanol liquid mixtures. The measured relative permittivity, which is the real part of complex permittivity, ranges from 8.58 to 66.12, which is simply limited by the choice of test materials available in our laboratory, not any other technical considerations of the sensor. The fabricated sensor prototype requires a very small liquid volume of less than 7 µl, while still offering an overall accuracy of better than 3 %, as compared to the commercial and other published works. Key advantages of the proposed sensor are that it combines 1.) a very low-profile planar and miniaturized structure sensing microliter liquid volume; 2.) ease of design and fabrication, which makes it cost-effective to manufacture and 3.) noninvasive and contactless measurements. Moreover, since the microfluidic subsystem can potentially be detached from the SIW microwave sensor and, afterward, replaced by a new microfluidic component, the sensor can be reused with no life-cycle limitation and without degrading any figure of merit.

Abstract-This paper reports on a miniaturized lab-on-awaveguide liquid-mixture sensor, achieving highly-accurate nanoliter liquid sample characterization, for biomedical applications. The nanofluidic-integrated millimeter-wave sensor design is based on near-field transmission-line technique implemented by a single loop slot antenna operating at 91 GHz, fabricated into the lid of a photolaser-based subtractive manufactured WR-10 rectangular waveguide. The nanofluidic subsystem, which is mounted on top of the antenna aperture, is fabricated by using multiple Polytetrafluoroethylene (PTFE) layers to encapsulate and isolate the liquid sample during the experiment, hence, offering various preferable features e.g. noninvasive and contactless measurements. Moreover, the sensor is reusable by replacing only the nanofluidic subsystem, resulting a cost-effective sensor. The novel sensor can measure a liquid volume of as low as 210 nanoliters, while still achieving a discrimination accuracy of better than 2% of ethanol in the ethanol/deionized-water liquid mixture with a standard deviation of lower than 0.008 from at least three repeated measurements, resulting in the highest accurate ethanol and DI-water discriminator reported to date. The nanofluidic-integrated millimeter-wave sensor also offers other advantages such as ease of design, low fabrication and material cost, and no life-cycle limitation of the millimeter-wave subsystem.Index Terms-biomedical liquid mixtures, nanofluidic, millimeter-wave sensor, transmission line method, W-band.

This paper presents a 220-320-GHz hemispherical lens antenna fabricated using photopolymer-based additive manufacture and directly fed by the standard WR-3 rectangular waveguide without any additional waveguide extension. The microfabrication process is based on digital light processing rapid prototyping using the Monocure 3DR3582C resin-based photocurable polymer. This gives various key advantages, including ease of antenna fabrication, manufacturing speed, and cost-effectiveness due to its rapid fabrication capability. Even though the photopolymer is found to have a loss tangent of 0.034 at 320 GHz, the all-polymer lens antennas still achieve a fractional bandwidth of 37%, covering the whole 220-320-GHz WR-3 waveguide band with a measured gain of approximately 16 dBi at 0 • over the whole band. A measured return loss of better than 14 dB is achieved from 220 to 320 GHz with a half-power beamwidth of approximately 12 • , which is relatively constant over the whole WR-3 band. INDEX TERMS Lens antenna, digital light processing, terahertz antennas.

Abstract-In this paper we demonstrate a novel manufacturing technology for high-aspect-ratio vertical interconnects for highfrequency applications. This novel approach is based on magnetic self-assembly of pre-fabricated nickel wires that are subsequently insulated with a thermosetting polymer. The high-frequency performance of the through silicon vias (TSVs) is enhanced by depositing a gold layer on the outer surface of the nickel wires and by reducing capacitive parasitics through a low-k polymer liner. As compared to conventional TSV designs, this novel concept offers a more compact design and a simpler, potentially more cost-effective manufacturing process. Moreover, this fabrication concept is very versatile and adaptable to many different applications such as interposer, MEMS, or millimeter wave applications. For evaluation purposes, coplanar waveguides (CPW) with incorporated TSV interconnections were fabricated and characterized. The experimental results reveal a high bandwidth from DC to 86 GHz and an insertion loss of less than 0.53 dB per single TSV interconnection for frequencies up to 75 GHz.Index Terms-RF signal transmission, skin effect, vertical interconnection, wafer scale integration, through silicon via (TSV).

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