An X band RF MEMS switch based on silicon-on-glass architecture

Communication systems such as those used on satellite platforms demand high performance from individual components that make up the various systems and sub-systems. Switching and routing of RF signals between various modules is a routine and critical operation that determines the overall efficiency of the entire system. In this paper, we present the design and fabrication aspects of a direct contact RF MEMS switch designed to operate in the X band (8–12 GHz) with a target insertion of about 0·5 dB and isolation better than 30 dB. The actuation voltage is expected to be around 50 V. The die size is designed to be 3 mm (H) × 3 mm(W) × 2 mm(H). The switch is built from a low residual stress device layer of a highly conducting (0·005 Ohms-cm) silicon on insulator (SOI) wafer. After subsequent lithographic steps, the wafer is bonded to a Pyrex glass wafer which has been previously patterned with gold transmission lines and pull in electrodes. Being built from a single crystal silicon structure, the mechanical robustness of the actuator is much greater than the those in similar membrane-based devices. A 6 mask fabrication process utilizing Deep Reactive Ion Etching to achieve high aspect ratio stiction free structures was developed and implemented. Devices from the first fabrication run are being analysed in our laboratory.     

Thermal degradation of poly(ethylene oxide) and polyacrylamide with ascorbic acid

The degradation of poly(ethylene oxide) and polyacrylamide in aqueous solution was studied with ascorbic acid. Gel permeation chromatograph was used to monitor molecular weight dynamics with time. A model based on continuous distribution kinetics showed that the experimental data matched well with theory. The results showed that the degradation of polymers is significantly enhanced in the presence of ascorbic acid. The degradation rate initially increased with ascorbic acid concentration but was independent of it at higher concentrations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3067–3072, 2006     

Femtosecond pulsed laser micromachining of glass substrates with application to microfluidic devices

We describe a technique for surface and subsurface micromachining of glass substrates by using tightly focused femtosecond laser pulses at a wavelength of 1660 nm. A salient feature of pulsed laser micromachining is its ability to drill subsurface tunnels into glass substrates. To demonstrate a potential application of this micromachining technique, we fabricate simple microfluidic structures on a glass plate. The use of a cover plate that seals the device by making point-to-point contact with the flat surface of the substrate is necessary to prevent the evaporation of liquids in open channels and chambers. Methods for protecting and sealing the micromachined structures for microfluidic applications are discussed.     

Production of syngas from steam reforming and CO removal with water gas shift reaction over nanosized Zr0.95Ru0.05O2−δ solid solution

This study presents the synthesis, characterization, and kinetics of steam reforming of methane and water gas shift (WGS) reactions over highly active and coke resistant Zr_0.95Ru_0.05O_2−δ. The catalyst showed high activity at low temperatures for both the reactions. For WGS reaction, 99% conversion of CO with 100% H₂ selectivity was observed below 290 °C. The detailed kinetic studies including influence of gas phase product species, effect of temperature and catalyst loading on the reaction rates have been investigated. For the reforming reaction, the rate of reaction is first order in CH₄ concentration and independent of CO and H₂O concentration. This indicates that the adsorptive dissociation of CH₄ is the rate determining step. The catalyst also showed excellent coke resistance even under a stoichiometric steam/carbon ratio. A lack of CO methanation activity is an important finding of present study and this is attributed to the ionic nature of Ru species. The associative mechanism involving the surface formate as an intermediate was used to correlate experimental data.     

Photocatalytic degradation of Azure and Sudan dyes using nano TiO2

The present study investigates the dependence of photocatalytic rate on molecular structure of the substrate that is degraded. The photocatalytic degradation of Azure (A and B) and Sudan (III and IV) dyes, having similar structure, but different functional groups, were investigated with two catalysts. The photocatalytic activity of solution combustion synthesized TiO(2) (CS TiO(2)) was compared with that of Degussa P-25 for degrading these dyes. The effect of solvents and mixed-solvent system on photodegradation of Sudan III was investigated. The photodegradation rate was found to be higher in solvents with higher polarity. The effect of pH and the presence of metal ions in the form of chloride and nitrate salt, on degradation rate of Azure A was also investigated. The metal ions significantly reduced the photocatalysis rates. A detailed Langmuir-Hinshelwood kinetic model has been developed to explain the effect of metal ions on degradation rate of the substrate. This model elucidates the contribution of holes and electrons towards degradation of the dye.     

Combustion synthesized vanadia rods for environmental applications

Rod‐shaped V₂O₅ was synthesized using the solution combustion technique, and the morphology of the compound was confirmed by TEM. Rods of an average diameter of 500 nm and length 3–6 times the diameter were obtained after the calcination of freshly prepared V₂O₅ at 550°C for 24 h. Pd metal nanoparticles of 20 nm size were deposited onto the rods using the wet impregnation technique. The as‐synthesized, calcined and Pd impregnated V₂O₅ were characterized by a wide variety of techniques including energy dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy. These compounds were tested for CO oxidation, adsorption, and photocatalytic degradation of dyes. The 1% Pd/V₂O₅ showed a high activity for CO oxidation, the as‐synthesized compound showed activity for the adsorption of cationic dyes, whereas the calcined V₂O₅ sample showed high rates of photocatalytic degradation of dyes. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

An enzymatic/acid-catalyzed hybrid process for biodiesel production from soybean oil

The present study is aimed at developing an enzymatic/acid-catalyzed hybrid process for biodiesel production using soybean oil as feedstock. In the enzymatic hydrolysis, 88% of the oil taken initially was hydrolyzed by binary immobilized lipase after 5 h under optimal conditions. The hydrolysate was further used in acid-catalyzed esterification for biodiesel production and the effects of temperature, catalyst concentration, feedstock to methanol molar ratio, and reaction time on biodiesel conversion were investigated. By using a feedstock to methanol molar ratio of 1:15 and a sulfuric acid concentration of 2.5%, a biodiesel conversion of 99% was obtained after 12 h of reaction at 50 °C. The biodiesel produced by this process met the American Society for Testing and Materials (ASTM) standard. This hybrid process may open a way for biodiesel production using unrefined and used oil as feedstock.     

In Vitro Prostate Cancer Treatment via CRISPR-Cas9 Gene Editing Facilitated by Polyethyleneimine-Derived Graphene Quantum Dots

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas9 (CRISPR associated protein 9) is a programmable gene editing tool with a promising potential for cancer gene therapy. This therapeutic function is enabled in the present study via the non-covalent delivery of CRISPR ribonucleic protein (RNP) by cationic glucosamine/PEI-derived graphene quantum dots (PEI-GQDs) that aid in overcoming physiological barriers and tracking genes of interest. PEI-GQD/RNP complex targeting the tumor protein 53 (TP53) gene mutation overexpressed in ∽50% of cancers successfully produces its double-stranded breaks in solution and in prostate cancer (PC-3) cells. Restoring this cancer “suicide” gene can promote cellular repair pathways and lead to cancer cell apoptosis. Its repair to the healthy form performed by simultaneous PEI-GQD delivery of CRISPR RNP and a gene repair template leads to a successful therapeutic outcome: 40% apoptotic cancer cell death, while having no effect on non-cancerous (HeK293) cells. The translocation of PEI-GQD/RNP complex into PC-3 cell cytoplasm is tracked via GQD intrinsic fluorescence, while enhanced green fluorescent protein (EGFP)-tagged RNP is detected in the cell nucleus, showing the successful detachment of the gene editing tool upon internalization. Using GQDs as non-viral delivery and imaging agents for CRISPR-Cas9 RNP sets the stage for image-guided cancer-specific gene therapy.