scholarly journals A Microwave Platform for Reliable and Instant Interconnecting Combined with Microwave-Microfluidic Interdigital Capacitor Chips for Sensing Applications

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1687
Author(s):  
Juncheng Bao ◽  
Gertjan Maenhout ◽  
Tomislav Markovic ◽  
Ilja Ocket ◽  
Bart Nauwelaers
Keyword(s):  
Dielectric Permittivity ◽  
High Frequency ◽  
Quartz Substrate ◽  
Microfluidic Chips ◽  
Interdigital Capacitor ◽  
Sensing Applications ◽  
Pdms Channel ◽  
Spring System ◽  
Lift Off ◽  
The Stability

This work presents a novel platform conceived as an interconnect box (ICB) that brings high-frequency signals from microwave instruments to consumable lab-on-a-chip devices. The ICB can be connected to instruments with a standard coaxial connector and to consumable chips by introducing a spring-levered interface with elastomer conductive pins. With the spring-system, microwave-microfluidic chips can be mounted reliably on the setup in a couple of seconds. The high-frequency interface within the ICB is protected from the environment by an enclosure having a single slit for mounting the chip. The stability and repeatability of the contact between the ICB and inserted consumable chips are investigated to prove the reliability of the proposed ICB. Given the rapid interconnecting of chips using the proposed ICB, five different interdigital capacitor (IDC) designs having the same sensing area were investigated for dielectric permittivity extraction of liquids. The designed IDCs, embedded in a polydimethylsiloxane (PDMS) channel, were fabricated with a lift-off gold patterning technology on a quartz substrate. Water–Isopropanol (IPA) mixtures with different volume fractions were flushed through the channel over IDCs and sensed based on the measured reflection coefficients. Dielectric permittivity was extracted using permittivity extraction techniques, and fitted permittivity data shows good agreement with literature from 100 to 25 GHz.

The Role of Hydrophobicity in the Stability and pH-Switchability of (RXDX)4 and Coumarin-RXDX Conjugate β-Sheets

2020 ◽  
Author(s):  
Ryan Weber ◽  
Martin McCullagh
Keyword(s):  
Biological Imaging ◽  
Ph Sensing ◽  
Hydrophobic Residue ◽  
Ideal Candidate ◽  
Self Assembling ◽  
Sensing Applications ◽  
Β Sheets ◽  
The Stability ◽  
Dynamics Simulations

<p>pH-switchable, self-assembling materials are of interest in biological imaging and sensing applications. Here we propose that combining the pH-switchability of RXDX (X=Ala, Val, Leu, Ile, Phe) peptides and the optical properties of coumarin creates an ideal candidate for these materials. This suggestion is tested with a thorough set of all-atom molecular dynamics simulations. We first investigate the dependence of pH-switchabiliy on the identity of the hydrophobic residue, X, in the bare (RXDX)<sub>4</sub> systems. Increasing the hydrophobicity stabilizes the fiber which, in turn, reduces the pH-switchabilty of the system. This behavior is found to be somewhat transferable to systems in which a single hydrophobic residue is replaced with a coumarin containing amino acid. In this case, conjugates with X=Ala are found to be unstable and both pHs while conjugates with X=Val, Leu, Ile and Phe are found to form stable β-sheets at least at neutral pH. The (RFDF)<sub>4</sub>-coumarin conjugate is found to have the largest relative entropy value of 0.884 +/- 0.001 between neutral and acidic coumarin ordering distributions. Thus, we posit that coumarin-(RFDF)<sub>4</sub> containing peptide sequences are ideal candidates for pH-sensing bioelectronic materials.</p>

scholarly journals Delay compensation based controller for rotary electrohydraulic servo system

2021 ◽  
Author(s):  
Zakarya Omar ◽  
Xingsong Wang ◽  
Khalid Hussain ◽  
Mingxing Yang
Keyword(s):  
High Frequency ◽  
Dead Time ◽  
Sliding Mode ◽  
Servo System ◽  
Smith Predictor ◽  
Delay Compensation ◽  
Mechanical Parts ◽  
System Output ◽  
Electrohydraulic Servo System ◽  
The Stability

AbstractThe typical power-assisted hip exoskeleton utilizes rotary electrohydraulic actuator to carry out strength augmentation required by many tasks such as running, lifting loads and climbing up. Nevertheless, it is difficult to precisely control it due to the inherent nonlinearity and the large dead time occurring in the output. The presence of large dead time fires undesired fluctuation in the system output. Furthermore, the risk of damaging the mechanical parts of the actuator increases as these high-frequency underdamped oscillations surpass the natural frequency of the system. In addition, system closed-loop performance is degraded and the stability of the system is unenviably affected. In this work, a Sliding Mode Controller enhanced by a Smith predictor (SMC-SP) scheme that counts for the output delay and the inherent parameter nonlinearities is presented. SMC is utilized for its robustness against the uncertainty and nonlinearity of the servo system parameters whereas the Smith predictor alleviates the dead time of the system’s states. Experimental results show smoother response of the proposed scheme regardless of the amount of the existing dead time. The response trajectories of the proposed SMC-SP versus other control methods were compared for a different predefined dead time.

scholarly journals Sintering, Microstructure, and Dielectric Properties of Copper Borates for High Frequency LTCC Applications

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4017
Author(s):  
Dorota Szwagierczak ◽  
Beata Synkiewicz-Musialska ◽  
Jan Kulawik ◽  
Norbert Pałka
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
High Frequency ◽  
Ceramic Materials ◽  
Sintering Behavior ◽  
Terahertz Time Domain Spectroscopy ◽  
Very High Frequency ◽  
X Ray ◽  
Low Dielectric ◽  
Very High

New ceramic materials based on two copper borates, CuB2O4 and Cu3B2O6, were prepared via solid state synthesis and sintering, and characterized as promising candidates for low dielectric permittivity substrates for very high frequency circuits. The sintering behavior, composition, microstructure, and dielectric properties of the ceramics were investigated using a heating microscope, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and terahertz time domain spectroscopy. The studies revealed a low dielectric permittivity of 5.1–6.7 and low dielectric loss in the frequency range 0.14–0.7 THz. The copper borate-based materials, owing to a low sintering temperature of 900–960 °C, are suitable for LTCC (low temperature cofired ceramics) applications.

scholarly journals A Real-Time Method for Improving Stability of Monolithic Quartz Crystal Microbalance Operating under Harsh Environmental Conditions

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4166
Author(s):  
Román Fernández ◽  
María Calero ◽  
Yolanda Jiménez ◽  
Antonio Arnau
Keyword(s):  
Real Time ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Limit Of Detection ◽  
Quartz Substrate ◽  
Low Cost ◽  
Discrete Wavelet ◽  
Reagent Consumption ◽  
Measurement Cell ◽  
The Stability

Monolithic quartz crystal microbalance (MQCM) has recently emerged as a very promising technology suitable for biosensing applications. These devices consist of an array of miniaturized QCM sensors integrated within the same quartz substrate capable of detecting multiple target analytes simultaneously. Their relevant benefits include high throughput, low cost per sensor unit, low sample/reagent consumption and fast sensing response. Despite the great potential of MQCM, unwanted environmental factors (e.g., temperature, humidity, vibrations, or pressure) and perturbations intrinsic to the sensor setup (e.g., mechanical stress exerted by the measurement cell or electronic noise of the characterization system) can affect sensor stability, masking the signal of interest and degrading the limit of detection (LoD). Here, we present a method based on the discrete wavelet transform (DWT) to improve the stability of the resonance frequency and dissipation signals in real time. The method takes advantage of the similarity among the noise patterns of the resonators integrated in an MQCM device to mitigate disturbing factors that impact on sensor response. Performance of the method is validated by studying the adsorption of proteins (neutravidin and biotinylated albumin) under external controlled factors (temperature and pressure/flow rate) that simulate unwanted disturbances.

An Efficient Galerkin BEM to Compute High Acoustic Eigenfrequencies

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Mario Durán ◽  
Jean-Claude Nédélec ◽  
Sebastián Ossandón
Keyword(s):  
Numerical Method ◽  
Integral Equations ◽  
High Frequency ◽  
High Accuracy ◽  
Integral Representations ◽  
Stability And Convergence ◽  
Symmetric Matrices ◽  
Frequency Interval ◽  
Numerical Treatment ◽  
The Stability

An efficient numerical method, using integral equations, is developed to calculate precisely the acoustic eigenfrequencies and their associated eigenvectors, located in a given high frequency interval. It is currently known that the real symmetric matrices are well adapted to numerical treatment. However, we show that this is not the case when using integral representations to determine with high accuracy the spectrum of elliptic, and other related operators. Functions are evaluated only in the boundary of the domain, so very fine discretizations may be chosen to obtain high eigenfrequencies. We discuss the stability and convergence of the proposed method. Finally we show some examples.

SiGe Heteroepitaxy for High Frequency Circuits

1998 ◽  
Vol 525 ◽  
Author(s):  
B. Tillack ◽  
D. Bolze ◽  
G. Fischer ◽  
G. Kissinger ◽  
D. Knoll ◽  
...  
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
High Frequency ◽  
Defect Density ◽  
Process Capability ◽  
Chemical Vapor ◽  
Bipolar Transistors ◽  
Capability Indices ◽  
Data Points ◽  
B Doping ◽  
The Stability

ABSTRACTWe have determined the process capability of Low Pressure (Rapid Thermal) Chemical Vapor Deposition (LP(RT)CVD) of epitaxial Si/SiGe/Si stacks for heterojunction bipolar transistors (HIBTs). The transistor parameters primarily influenced by the epitaxial characteristics were measured for 600 identically processed 4” wafers. The results demonstrate that it is possible to control accurately the epitaxial process for a 25 nm thick graded SiGe base profile with 20 % Ge and very narrow B doping (5 nm). The pipe limited device yield of about 90 % for an emitter area of 104 μm2 indicates a very low defect density in the epitaxial layer stack. The process capability indices determined from about 40,000 data points demonstrate the stability and capability of the LP(RT)CVD epitaxy with regard to manufacturing requirements.

Fabrication of large area nanogap electrodes for sensing applications

2013 ◽  
Vol 1530 ◽  
Author(s):  
A. Bendavid ◽  
L. Wieczorek ◽  
R. Chai ◽  
J. S. Cooper ◽  
B. Raguse
Keyword(s):  
Large Scale ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Beam Current ◽  
Fabrication Method ◽  
Large Area ◽  
Sensor Applications ◽  
Sensing Applications ◽  
Lift Off ◽  
Nanogap Electrodes

ABSTRACTA large area nanogap electrode fabrication method combinig conventional lithography patterning with the of focused ion beam (FIB) is presented. Lithography and a lift-off process were used to pattern 50 nm thick platinum pads having an area of 300 μm × 300 μm. A range of 30-300 nm wide nanogaps (length from 300 μm to 10 mm ) were then etched using an FIB of Ga+ at an acceleration voltage of 30 kV at various beam currents. An investigation of Ga+ beam current ranging between 1-50 pA was undertaken to optimise the process for the current fabrication method. In this study, we used Monte Carlo simulation to calculate the damage depth in various materials by the Ga+. Calculation of the recoil cascades of the substrate atoms are also presented. The nanogap electrodes fabricated in this study were found to have empty gap resistances exceeding several hundred MΩ. A comparison of the gap length versus electrical resistance on glass substrates is presented. The results thus outline some important issues in low-conductance measurements. The proposed nanogap fabrication method can be extended to various sensor applications, such as chemical sensing, that employ the nanogap platform. This method may be used as a prototype technique for large-scale fabrication due to its simple, fast and reliable features.

Discrete-Time H-Infinity Synthesis of Frequency-Shaped Sliding Mode Control for Suppression of Vibration With Multiple Peak Frequencies

2016 ◽  
Author(s):  
Minghui Zheng ◽  
Masayoshi Tomizuka
Keyword(s):  
High Frequency ◽  
Sliding Mode ◽  
Disk Drive ◽  
Sliding Surface ◽  
Surface Dynamics ◽  
H Infinity ◽  
High Frequencies ◽  
Multiple Peak ◽  
Significant Performance ◽  
The Stability

Vibration with multiple large peaks at high frequencies may cause significant performance degradation and have become a major concern in modern high precision control systems. To deal with such high-frequency peaks, it is proposed to design a frequency-shaped sliding mode controller based on H∞ synthesis. It obtains an ‘optimal’ filter to shape the sliding surface, and thus provides frequency-dependent control allocation. The proposed frequency-shaping method assures the stability in the presence of multiple-peak vibration sources, and minimizes the weighted H∞ norm of the sliding surface dynamics. The evaluation is performed on a simulated hard disk drive with actual vibration sources from experiments, and the effectiveness of large vibration peak suppression is demonstrated.

Shallow subsurface mapping by electromagnetic sounding in the 300 kHz to 30 MHz range: Model studies and prototype system assessment

Geophysics ◽  
1994 ◽  
Vol 59 (8) ◽  
pp. 1201-1210 ◽  
Author(s):  
Duff C. Stewart ◽  
Walter L. Anderson ◽  
Thomas P. Grover ◽  
Victor F. Labson
Keyword(s):  
Dielectric Permittivity ◽  
High Frequency ◽  
Low Frequency ◽  
Computer Programs ◽  
Thin Layers ◽  
Depth Range ◽  
Frequency Range ◽  
Model Studies ◽  
New Instrument ◽  
Displacement Currents

A new instrument designed for frequency‐domain sounding in the depth range 0–10 m uses short coil spacings of 5 m or less and a frequency range of 300 kHz to 30 MHz. In this frequency range, both conduction currents (controlled by electrical conductivity) and displacement currents (controlled by dielectric permittivity) are important. Several surface electromagnetic survey systems commonly used (generally with frequencies less than 60 kHz) are unsuitable for detailed investigation of the upper 5 m of the earth or, as with ground‐penetrating radar, are most effective in relatively resistive environments. Most computer programs written for interpretation of data acquired with the low‐frequency systems neglect displacement currents, and are thus unsuited for accurate high‐frequency modeling and interpretation. New forward and inverse computer programs are described that include displacement currents in layered‐earth models. The computer programs and this new instrument are used to evaluate the effectiveness of shallow high‐frequency soundings based on measurement of the tilt angle and the ellipticity of magnetic fields. Forward model studies indicate that the influence of dielectric permittivity provides the ability to resolve thin layers, especially if the instrument frequency range can be extended to 50 MHz. Field tests of the instrument and the inversion program demonstrate the potential for detailed shallow mapping wherein both the resistivity and the dielectric permittivity of layers are determined. Although data collection and inversion are much slower than for low‐frequency methods, additional information is obtained inasmuch as there usually is a permittivity contrast as well as a resistivity contrast at boundaries between different materials. Determination of dielectric permittivity is particularly important for hazardous waste site characterization because the presence of some contaminants may have little effect on observed resistivity but a large effect on observed permittivity.

Effect of Reactant Preheating on the Stability of Non-Premixed Methane/Air Flames

2010 ◽  
Author(s):  
Sylvain Lamige ◽  
Ce´dric Galizzi ◽  
Jiesheng Min ◽  
Julien Perles ◽  
Fre´de´ric Andre´ ◽  
...  
Keyword(s):  
Room Temperature ◽  
Initial Temperature ◽  
Flame Stability ◽  
Air Velocity ◽  
Lifted Flames ◽  
Local Extinctions ◽  
Lift Off ◽  
Temperature Levels ◽  
The Stability ◽  
Jet Velocities

This study details the influence of reactant temperature on the stability of non-premixed CH4/air co-flow jet flames. Flame characteristics have been studied for five temperature levels (from 295 K to 600 K). The hysteresis zone formed by the limits between attached and lifted flame translates towards higher methane jet velocities with an increase of initial temperature, independently of the air velocity range. Moreover, critical velocities vary linearly with initial temperature. In addition, attachment and lift-off heights have been obtained from CH* chemiluminescence visualization. Results point out that the attachment height decreases significantly with temperature. Observations also indicate that the intrinsic process of lifting is modified. Pre-lifting anchored flame local extinctions, not observed at room-temperature, appear at higher initial temperatures; their occurrence increases with temperature. The lift-off height of turbulent lifted flames is also reduced with temperature. Overall, results show that increasing local temperature in the stabilization zone enhances flame stability.

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