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A state-of-the-art gas sensor is developed to measure extremely small concentrations of a chemical vapor in the air in a range lower than 0.1 parts per billion. The sensor enables simultaneous measurement of a chemical (methyl salicylate) with a resonant electromagnetic structure and radiating the information back to a base station. The chemical sensor is composed of a layer of graphene (transduction layer) with a molecular imprinting polymer (MIP) layer (sensor) on top. This leads to a combination of the ultra high sensitivity of graphene with the exquisite selectivity of the molecular imprinting technique (MIT). The sensor is electrically embedded within a patch antenna. The simulation results using Ansoft high-frequency structure simulator (HFSS) are presented along with test data that show parts per trillion (ppt) detection levels.

Alzheimer’s disease (AD) is a neurodegenerative disease, which affects millions of people worldwide. Curing this disease has not gained much success so far. Exhaled breath gas analysis offers an inexpensive, noninvasive, and immediate method for detecting a large number of diseases, including AD. In this paper, a new method is proposed to detect butylated hydroxytoluene (BHT) in the air, which is one of the chemicals found in the breath print of AD patients. A three-layer sensor was formed through deposition of a thin layer of graphene onto a glassy carbon substrate. Selective binding of the analyte was facilitated by electrochemically initiated polymerization of a solution containing the desired target molecule. Subsequent polymerization and removal of the analyte yielded a layer of polypyrrole, a conductive polymer, on top of the sensor containing molecularly imprinted cavities selective for the target molecule. Two sets of sensors have been developed. First, the graphene sensor has been fabricated with a layer of reduced graphene oxide (RGO) and tested over 5–100 part per million (ppm). For the second batch, Prussian blue was added to graphene before polymerization, mainly for enhancing the electrochemical properties. The sensor was tested over 0.02-1 parts per billion (ppb) level of concentration while the sensor resistance has been monitored.

Compact phase shifters with large phase shift, low loss, and high-power-handling capability are desired for a variety of applications. In this paper, a new type of compact meander line phase shifter with metallic perturber controlled by a piezoelectric transducer (PET) has been designed, fabricated, and tested. The new phase-shifter design led to a large phase shift of 360° with a control voltage of 50 V at 3.5 GHz, a low insertion loss of 1 ~ 3 dB, a wide range of operation frequency of 1 ~ 6 GHz, a high-power-handling capability beyond 30 dBm on a compact meander line of 18 mm × 18 mm, compared with similar phase shifters with a dielectric perturber which exhibited very limited phase shift at the S-band. In addition, this is a low-cost phase-shifter design that is extendable to the W -band and beyond. Combined with a low loss, large phase shift, compact size, and a high-power-handling capability, the new meander line phase shifter with PET-controlled metallic perturber showed great potential to be used in different RF/microwave systems.