Superparamagnetic iron oxide (Fe3O4) and highly anisotropic barium hexaferrite (BaFe12O19) nanoparticles were coated with an anti-inflammatory drug and magnetically transported through mucus produced by primary human airway epithelial cells. Using wet planetary ball milling, dl-2-amino-3-phosphonopropionic acid-coated BaFe12O19 nano-particles (BaNPs) of 1–100 nm in diameter were prepared in water. BaNPs and conventional 20–30-nm Fe3O4 nanoparticles (FeNPs) were then encased in a polymer (PLGA) loaded with dexamethasone (Dex) and tagged for imaging. PLGA-Dex-coated BaNPs and FeNPs were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) magnetometry. Both PLGA-Dex-coated BaNPs and FeNPs were transferred to the surface of a ~100-μm thick mucus layer of air-liquid interface cultured primary normal human tracheobronchial epithelial (NHTE) cells. Within 30 min, the nanoparticles were pulled successfully through the mucus layer by a permanent neodymium magnet. The penetration time of the nanomedicine was monitored using confocal microscopy and tailored by varying the thickness of the PLGA-Dex coating around the particles.

No abstract

Phased array radar systems are used for a wide variety of applications including the precise tracking of airborne craft for air traffic control and providing accurate atmospheric condition information important in weather forecasting. Reducing the cost and size of these radar systems will open new fields to the use of this technology. Using phase control implemented through liquid crystal materials we have created a compact, phased array radar system operating in the microwave range. We report on the construction and testing of a linear, eight element phased array antenna system operating at 32 GHz with element phase controlled by a dual frequency nematic liquid crystal media used as a tunable dielectric. The system was designed using CST Design Studios and Ansys HFSS software. Dual frequency liquid crystals are used to improve beam steering response times. We demonstrate 42 millisecond beam switching times, defined as the time to change the beam focus from one point to another point, controllable beam formation, and beam steering profiles consistent with analytical results and simulation models. The device footprint is a square with sides 9.5 cm long and a thickness less than 2.5 mm. Such a module is easily stackable to create an 8 × 8 phased array system. Our design incorporates a modular construction using PCB for the antennas and input circuitry and a liquid crystal phase control cell with microwave glass substrates. This design simplifies design, construction, and testing as compared to on-glass designs. The device shows an improvement in point-to-point scanning speeds by a factor of 3 as compared to similar liquid crystal based devices and provides continuously variable tuning. Such a device can be used in a system for reduced visibility, directional range finding suitable for automobile collision avoidance systems and rotary wing aircraft landing aids.

Electrically tunable double‐spurline notch filters with a nematic liquid crystal (LC) material as a dielectric medium were modeled, manufactured, and characterized. The spurlines, which were embedded into an inverted microstrip, consisted of quarter‐wavelength resonant elements. A Finite Difference Time Domain solver was used to model the filters. Photolithography and thin film deposition were employed to create the filters, followed by standard LC cell assembly. The filters, with central notch frequencies at 50 and 85 GHz, were characterized on‐wafer with a vector network analyzer. The stopband frequencies were tunable by 3% when a 14 volt peak‐to‐peak AC bias was applied across the 38 μm thick LC layer (electric field of 0.19 V/μm). The minimum stopband insertion loss of both filters achieved lower than −50 dB, while the stopband return loss varied from −4 to −12 dB. The −3 dB passband widths of the stopband filters were 12.2 and 28.3 GHz for the 50 and 85 GHz filters, respectively, giving a Q‐factor of 3–4.

Ferroelectric/ferromagnetic thin film heterostructures, SrBi2Ta2O9/BaFe12O19 (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

Fabrication of a thermotropic ferronematic colloid is reported, consisting of a 1% concentration of magnetite nanorods dispersed in a commercially obtained liquid crystal (LC). To produce the nanorods, solvothermal synthesis was utilized by adding Fe(CO) 5 to a reaction solution of hexadecylamine and oleic acid in n-octanol. The procedure allows for tailoring of the size and shape of the nanorods. The magnetic nanorods were functionalized with oleic acid. Magneto-optic and electro-optic properties of the colloid were characterized. Specifically, static measurements were performed to determine the birefringence and magnetic and electric Freedericksz thresholds. From the dynamic measurements, the switching time was determined. The nanorods increased the effective magnetic anisotropy of the LC. Depending on nanorod dimensions, the colloid demonstrated faster switching speeds, especially in the presence of crossed electric and magnetic fields.

No abstract