Search query: Fluidics in microwave components

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abstract: Thanks to the efforts of various research groups over the past decade in the area of tunable microwave passive components, the idea of tunability has become very well established within the RF/microwave community [1] [5] Many different designs have shown that tunable microwave components can improve the performance of a radio system in many ways. The tunability of microwave components has been realized using semiconductor devices (such as varactors or p i n diodes) and microelectromechanical systems (MEMS) devices. While these offer many advantages, such as high quality factor and high bandwidth operation (mainly for MEMS devices) and fast switching speeds (mainly for varactors and p i n diodes) they come with two major drawbacks.
author_names: Kamran Entesari

Alireza Pourghorban Saghati
title: Fluidics in Microwave Components
venue: IEEE Microwave Magazine
year: 2016

abstract: These days it seems that every research institution has a program to develop MEMS components; sensors, switches, optics, or fluidics. Some of these components are already finding their way into the marketplace, and MEMS/microelectronic systems on a chip are already being designed. HRL Laboratories, LLC, as been building RF MEMS switches for the last three years. [1,2] The design and fabrication of metal metal contact cantilever switches on GaAs substrates, and the measured performance of the switches will be presented, including switching speed, insertion loss, and isolation. Some examples of how these switches can be integrated into simple filters and antenna elements will be exhibited to show the potential for MEMS applications in electronic systems Microwave and millimeter wave phased array antennas typically operate over a narrow bandwidth, but for many applications multiple frequency operation would be highly desirable. This would require either a tunable antenna element with a multiband feed network or a multiband antenna array and the tunable feed network. PIN diodes and ferrites have been used for decades as tuning devices for antennas [3,4] Recently, optoelectronically tunable antennas have been reported [5 7] where photoconductive switches are used to connect dipole segments for frequency tuning or beam scanning. With the advent of MEMS processing, new RF switch structures are possible, and have the advantages over the other tuning techniques in simplicity, ultralow insertion loss, high isolation, power efficiency, and compactness. Two canonical RF MEMS switch structures are being actively developed, the capacitive switch and the contacting switch. The capacitive switch uses a metal membrane that is physically in contact with the ground electrode of a planar transmission line. A DC voltage causes opposite charges to be induced between the membrane and the ground electrode, which in turn results in an attractive force which pulls the membrane toward the oppositely charged electrode. A thin dielectric insulator (on the order of a few microns) prevents the switch from shorting. The effective RF capacitance of this switch increases from the switch "off" state to the switch "on: state, with an on off capacitance ratio up to the order of 100 [8] Reliable contacts are essential for the metal contact RF MEMS switch, which depends on the making and breaking of an actual metal to metal joint, a feat complicated by the low forces available from microactuation. In the force regime of tens to hundreds of micronewtons, surface states, adsorbed contaminants, and nanometerdepth material properties dominate the properties of metallic contact, and limited information has been available to the MEMS switch designer. Recent studies into this phenomenon by [9] have determined useful design criteria for pure gold contacts electroplated from sodium sulfite solution. Based on this work and other recent low force contact studies [10,11] switch designs were developed to provide 200 uN of contact force per contact and maximal heat sinking to the substrate. During the past three years, HRL Laboratories has developed a metal contact RF MEMS switch for operation up through 40 GHz, and beyond. The design and fabrication of the switches will be presented in this paper. In addition, the performance of this switch, including some limited lifetime data and power handling capability, will be provided. Finally, examples of the integration of these switches into frequency tuned filters and antennas will demonstrate the potential application of these switches to subsystem components. 2. CANTILEVER RF MEMS SWITCH CONFIGURATION AND PERFORMANCE The RF MEMS switch, shown in figure 1, has a suspended cantilever trilayer structure of metal sandwiched between insulating layers to improve the thermal stability of the devices and reduce the effect of as fabricated stress mismatch between the layers. A microphotograph of the switch is shown in figure 2. The cantilever beam includes the top actuation electrode and the RF switch. The actuation electrodes are isolated from the RF transmission line, thus no bias circuit is required for this switch. In addition, the switch actuation, being electrostatic, does not draw any DC current (there is a very small transient capacitance charging current) thus the required power for applications where arrays of switches are needed can remain reasonable.
author_names: Robert Y Loo

Gregory L Tangonan

Daniel F Sievenpiper

James H Schaffner

T Y Hsu

Hui-Pin Hsu
title: Reconfigurable Antenna Elements Using RF MEMS Switches
year: 2000

abstract: Abstract Background Microwave assisted extraction (MAE) have gained enormous popularity as a preferred method for the recovery of various active compounds from food materials. They proffer benefits such as the reduction of extraction time, environmental friendliness, low cost and enable automation or on line coupling to other analytical procedures. Recently, newer add ons or technological modifications have been incorporated into MAE systems, in an effort to continuously improve extraction efficiency and ensure a greener implementation. Scope and approach The core pathways of such meliorations include integrating microwave extraction with other technologies, e.g. ultrasound assisted extraction (UAE) negative pressure cavitation (NPC) enzyme assisted extraction (EAE) hydrodiffusion extraction (HDE) and supercritical fluid extraction (SFE) or replacement of extraction medium with suitable alternatives including ionic liquids, deep eutectic solvents, non ionic surfactants, etc. This review confers their underlying principles and mechanisms, equipment and apparatuses, practicalities, as well as resultant benefits such as increased yield, intensification of mass transfer and reduction of energy consumption, in a manner not achievable by MAE alone or previous intermediary modifications. Key findings and conclusions It is hoped that this paper reinforces the need to initiate more studies focused on process validation and optimization of such emerging MAE systems, in furtherance of their scale up, sustainability and robust adoption by the food industry.
author_names: Flora-Glad Chizoba Ekezie

Da-Wen Sun

Jun-Hu Cheng
title: Acceleration of microwave assisted extraction processes of food components by integrating technologies and applying emerging solvents: A review of latest developments
year: 2017

abstract: Abstract Microwave assisted pyrolysis (MWAP) provides distinctive heating for the conversion of coal into liquid fuels. This work investigated the effects of MWAP on the microstructure of bituminous coals by using Fourier transform infrared spectroscopy (FTIR) mercury intrusion porosimetry (MIP) and Scanning Electron Microscope (SEM) techniques. FTIR results showed that MWAP can lead to the decomposition of oxygen functional groups and aliphatic hydrocarbons. Removal of these hydrophilic groups significantly weakens the hydrophilicity of coal. With continuous exposure to microwaves, unstable components such as alcohol, phenol and carboxylic acid are converted into ether groups. Cyclization and aromatization induced by microwave heating improve the maturation of coal. MIP and SEM results indicated that the jet force exerted by the high pressure steam and gaseous products under MWAP gives a great boost to the opening, enlargement and connection of pores. Furthermore, the thermal stresses induced by microwave selective heating enlarge the fractures and create new cracks, providing seepage space for fluids. MWAP of bituminous coals can not only release moisture and volatiles but also create seepage space by modifying the pore and fracture structure.
author_names: He Fei Li

Shiliang Shi

Bai-quan Lin

Jiexin Lu

Qing Ye

Yonghua Lu

Zheng Wang

Yi-du Hong

Xiangnan Zhu
title: Effects of microwave assisted pyrolysis on the microstructure of bituminous coals
venue: Energy
year: 2019

abstract: Tamarind (Tamarindus indica) belongs to the family Leguminosae. It is commonly growing in tropical and subtropical regions now and is one of the most important plant resources as cuisine materials. Antioxidative activity of tamarind seeds was investigated. An ethanol extract prepared from the seed coat contained antioxidative activity as measured by the thiocyanate and thiobarbituric acid (TBA) method. Essential oils are highly odorous droplets found in minimal quantities in the flowers, stems, leaves, roots and barks of aromatic plants. They are not recognized as true oils as the vegetable oils, but highly fluid and volatile. Experts recognize an essential oil by its aroma and test the oil characteristics such as vaporization and crystallization point using Differential Scanning Calorimetry (DSC) DSC has emerged as a powerful experimental technique for determining thermodynamic properties of biomacromolecules [1] Volatile components of tamarind leaves and seed locally grown will be isolated by Microwave Assisted Extraction (MAE) The presence of essential oil as the volatile components will be investigated to determine whether this method is effective or not to extract the oil from tamarind leaves and seed. The parameters that will be measured are the time for the oil droplets formation and the optimum temperature for the extraction of oil. At the end of the extraction, amber color oil was obtained. Results showed that the time for the oil droplets formation increasing with the increasing weight of sample for both tamarind leaves and seed samples. The optimum temperature for the extraction obtained was 125 oC with the yield of 1.2 mL of seed oil. The vaporization and crystallization point of oil are presented in the DSC curve and the specific heat capacity of the oil are calculated.
author_names: M A Zawawi

Ahmed H A Dabwa

Lili Shakira Hassan
title: EXTRACTION OF ESSENTIAL OILS FROM TAMARIND LEAVES AND SEED USING MICROWAVE EXTRACTION
year: 2020

abstract: Characterization of selenium nanoparticles and selenium nanoparticle human serum albumin conjugates prepared in nanopowder form, their elemental composition, and particle size distribution were investigated with a microwave plasma optical emission spectrometry operating in a single particle mode. This new analytical technique was used for the first time to examine the molecular interaction between selenium nanoparticles and human serum albumin regarding potential biomedical applications of selenium nanoparticles. Nanopowder sample was introduced to a helium plasma by pneumatic nebulization based on fluidized bed approach and measured with a time resolution of 20 ms. Both selenium nanoparticles and selenium nanoparticle human serum albumin conjugates were characterized by observation of synchronous signals from different particle components. Plots of the time correlation between Se and C signals for all particles in selenium nanoparticles and selenium nanoparticle human serum albumin conjugates samples differed from each other in degree of correlation and synchronicity of recorded signals. The interaction between selenium nanoparticles and human serum albumin was confirmed using Bradford assay. For selenium nanoparticles synthesized using yeast cells, the percentage of bound protein was only of 4% whereas for selenium nanoparticles synthesized using yeast extract as a stabilizing agent it was 16%
author_names: Magdalena Borowska

Ewelina Pawlik

Krzysztof Jankowski
title: Investigation of interaction between biogenic selenium nanoparticles and human serum albumin using microwave plasma optical emission spectrometry operating in a single particle mode
venue: Monatshefte fur Chemie Chemical Monthly
year: 2020

abstract: Surface phenomenon such as cavitation erosion corrosion limits the working life and durability of the fluid machines through significantly altering the efficiency. Surface modification is an apparent and economical route for improving the sustainability of these components. Recently developed complex concentrated alloys (CCAs) or high entropy alloys (HEAs) possess exceptional properties owing to high configurational entropy. We developed CCA coatings on the stainless steel using a facial and effective microwave processing technique. The effect of Al molar fraction in AlxCoCrFeNi (x 0.1 3) CCAs on ultrasonic cavitation erosion corrosion was investigated in 3.5% NaCl solution. For comparison, cavitation erosion and electrochemical corrosion behavior of the pre and post tested samples was also performed. Detailed microstructure and mechanical characterization of the developed coatings were also preformed using different analytical techniques. The equimolar CCA coating showed apical degradation resistance under both pure erosion and erosion corrosion conditions. The observed behavior is attributed to high strain hardening, optimal hardness, fracture toughness, and utmost stability of the passive layer. The phenomenal conjugation of these properties was associated with highest configurational entropy for equimolar composition resulting in sluggish diffusion, and severe lattice straining. Compared to pits, striations and cracks characterizing the morphology of the degraded stainless steel, the equimolar and Al0.1CoCrFeNi CCAs showed TTS (tearing topograph surface) as the dominant failure mode characterized by presence of microplastic deformation. The degradation of the Al3CoCrFeNi CCA occurred mainly through brittle failure mode. The difference in failure mechanism is related to the mechanical properties and underlying microstructure.
author_names: Rakesh B Nair

Harpreet Singh Arora

Harpreet Singh Grewal
title: Microwave synthesized complex concentrated alloy coatings: Plausible solution to cavitation induced erosion corrosion.
venue: Ultrasonics sonochemistry
year: 2019

abstract: This article presents a frequency reconfigurable RF impedance tuner using eight cascaded fluidic cells to cover the frequency band [0.9, 2.4] GHz. The tuner is made of eight fluidic fillable cavities on top of a coplanar waveguide transmission line in a single low temperature cofired ceramic (LTCC) substrate. Each cavity is either kept empty or filled with deionized (DI) water to alter the substrate's permittivity and so change the tuner's response. Closed form expressions are derived and used to dimension the tuner's individual cells, while 3 D field simulations are used to complete the design of a single cell and an entire eight cell tuner. Both components are fabricated, and good agreement between simulation and measured is observed. The fabricated tuner is used to build a fluidic reconfigurable RF amplifier.
author_names: Dorra Bahloul

Ammar B Kouki
title: LTCC Based Fluidic Tuners for Low Microwave Frequency Reconfigurable Circuits
venue: IEEE Transactions on Microwave Theory and Techniques
year: 2020

abstract: The tumor detection performance of two air based metallic microwave breast imaging systems is evaluated experimentally using breast phantoms having realistic tissue permittivities. The first system has a circular cylindrical shape, whereas the second has a faceted hemispherical shape. No immersion medium is utilized making these systems low loss quasi resonant structures. The breast phantoms are composed of three distinct volumes representing structurally simplified adipose, fibroglandular, and tumor regions filled with tissue mimicking fluids. Scattered field data are collected, at multiple frequencies, on the inside surface of the chambers: the normal component of the electric field at 18 locations in the cylindrical chamber and 24 tangential magnetic field components in the faceted chamber. Quantitative 3 D imaging of these high contrast phantoms is performed utilizing the finite element contrast source inversion algorithm wherein an inhomogeneous numerical background, constituting prior information, is introduced. Experiments are conducted with various accuracies of this prior information, both in terms of the permittivity that is used as well as the accuracy of the geometry compared with the true regions within the phantom. Image segmentation techniques based on thresholding the 3 D reconstructed images are evaluated for tumor detection. Utilizing receiver operating characteristic (ROC) curves, it is shown that taking the intersection of multifrequency thresholded 3 D images performs the best for detecting tumors.
author_names: Mohammad Asefi

Anastasia Baran

Joe Lovetri
title: An Experimental Phantom Study for Air Based Quasi Resonant Microwave Breast Imaging
venue: IEEE Transactions on Microwave Theory and Techniques
year: 2019

abstract: This paper compares two types of microfluidic sensors that are designed for operation in ISM (Industrial, Scientific, Medical) bands at microwave frequencies of 2.45 GHz and 5.8 GHz. In the case of the first sensor, the principle of operation is based on the resonance phenomenon in a microwave circuit filled with a test sample. The second sensor is based on the interferometric principle and makes use of the superposition of two coherent microwave signals, where only one goes through a test sample. Both sensors are monolithic structures fabricated using low temperature co fired ceramics (LTCCs) The LTCC based microwave microfluidic sensor properties are examined and compared by measuring their responses for various concentrations of two types of test fluids: one is a mixture of water/ethanol, and the other is dopamine dissolved in a buffer solution. The experiments show a linear response for the LTCC based microwave microfluidic sensors as a function of the concentration of the components in both test fluids.
author_names: Karol Malecha

Laura Jasinska

Anna Grytsko

Kamila Drzozga

Piotr M Slobodzian

Joanna Cabaj
title: Monolithic Microwave Microfluidic Sensors Made with Low Temperature Co Fired Ceramic (LTCC) Technology
venue: Sensors
year: 2019