Nonlinear macromodel based on Krylov subspace for micromixer of the microfluidic chip

The simulation of MEMS (Micro-Electro-Mechanical-System) containing fluid field could not be well performed by conventional numerical analysis methods. The micro flow field characteristics can be simulated by using macromodel including a nonlinear analysis. This paper set up the macromodel of the micromixer of the microfluidic chip using Krylov subspace projection method. The system functions were assembled through finite element analysis using COMSOL. We took the flow field-concentration field analysis for micromixer finite element model. The finite element functions order is reduced by second-order Krylov subspace projection method based on Lanczos algorithm. It can be shown that the simulation results obtained by using the macromodel are highly consistent with the results of finite element analysis. The calculation using the macromodel is two orders of magnitude faster than the calculation performed by the finite element analysis method. This macromodel should facilitate the design of microfluidic devices with sophisticated channel networks

Evaluation of commercial ADC radiation tolerance for accelerator experiments

Electronic components used in high energy physics experiments are subjected to a radiation background composed of high energy hadrons, mesons and photons. These particles can induce permanent and transient effects that affect the normal device operation. Ionizing dose and displacement damage can cause chronic damage which disable the device permanently. Transient effects or single event effects are in general recoverable with time intervals that depend on the nature of the failure. The magnitude of these effects is technology dependent with feature size being one of the key parameters. Analog to digital converters are components that are frequently used in detector front end electronics, generally placed as close as possible to the sensing elements to maximize signal fidelity. We report on radiation effects tests conducted on 17 commercially available analog to digital converters and extensive single event effect measurements on specific twelve and fourteen bit ADCs that presented high tolerance to ionizing dose. Mitigation strategies for single event effects (SEE) are discussed for their use in the large hadron collider environment.Comment: 16 pages, 8 figure

Development of COTS ADC SEE Test System for the ATLAS LAr Calorimeter Upgrade

Radiation-tolerant, high speed, high density and low power commercial off-the-shelf (COTS) analog-to-digital converters (ADCs) are planned to be used in the upgrade to the Liquid Argon (LAr) calorimeter front end (FE) trigger readout electronics. Total ionization dose (TID) and single event effect (SEE) are two important radiation effects which need to be characterized on COTS ADCs. In our initial TID test, Texas Instruments (TI) ADS5272 was identified to be the top performer after screening a total 17 COTS ADCs from different manufacturers with dynamic range and sampling rate meeting the requirements of the FE electronics. Another interesting feature of ADS5272 is its 6.5 clock cycles latency, which is the shortest among the 17 candidates. Based on the TID performance, we have designed a SEE evaluation system for ADS5272, which allows us to further assess its radiation tolerance. In this paper, we present a detailed design of ADS5272 SEE evaluation system and show the effectiveness of this system while evaluating ADS5272 SEE characteristics in multiple irradiation tests. According to TID and SEE test results, ADS5272 was chosen to be implemented in the full-size LAr Trigger Digitizer Board (LTDB) demonstrator, which will be installed on ATLAS calorimeter during the 2014 Long Shutdown 1 (LS1).Comment: 8 pages, 14 figure

Meningitic Escherichia coli K1 Penetration and Neutrophil Transmigration Across the Blood–Brain Barrier are Modulated by Alpha7 Nicotinic Receptor

Alpha7 nicotinic acetylcholine receptor (nAChR), an essential regulator of inflammation, is abundantly expressed in hippocampal neurons, which are vulnerable to bacterial meningitis. However, it is unknown whether α7 nAChR contributes to the regulation of these events. In this report, an aggravating role of α7 nAChR in host defense against meningitic E. coli infection was demonstrated by using α7-deficient (α7-/-) mouse brain microvascular endothelial cells (BMEC) and animal model systems. As shown in our in vitro and in vivo studies, E. coli K1 invasion and polymorphonuclear neutrophil (PMN) transmigration across the blood-brain barrier (BBB) were significantly reduced in α7-/- BMEC and α7-/- mice. Stimulation by nicotine was abolished in the α7-/- cells and animals. The same blocking effect was achieved by methyllycaconitine (α7 antagonist). The tight junction molecules occludin and ZO-1 were significantly reduced in the brain cortex of wildtype mice infected with E. coli and treated with nicotine, compared to α7-/- cells and animals. Decreased neuronal injury in the hippocampal dentate gyrus was observed in α7-/- mice with meningitis. Proinflammatory cytokines (IL-1β, IL-6, TNFα, MCP-1, MIP-1alpha, and RANTES) and adhesion molecules (CD44 and ICAM-1) were significantly reduced in the cerebrospinal fluids of the α7-/- mice with E. coli meningitis. Furthermore, α7 nAChR is the major calcium channel for nicotine- and E. coli K1-increased intracellular calcium concentrations of mouse BMEC. Taken together, our data suggest that α7 nAChR plays a detrimental role in the host defense against meningitic infection by modulation of pathogen invasion, PMN recruitment, calcium signaling and neuronal inflammation

Design and Simulation for a Two-dimensional Rectangle-Square Wave Micromixer

An effective two-dimensional micromixer named rectangle-square wave micromixer with very simple structure has been presented. The rectangle-square wave micromixer based on split and recombination principle was simulated to analyze the fluid flow and the mixing efficiency. The flow rate, sample concentration, pressure drop at different position in the micromixer was researched. The simulation results show the micromixer can appear good performance for a wide range of flow rates with smaller pressure drop. The rectangle-square wave micromixer is proven to be effective and will have great potential to be integrated to other microfluidic systems

Particle separation in microfluidics using different modal ultrasonic standing waves

Microfluidic technology has great advantages in the precise manipulation of micro and nano particles, and the separation of micro and nano particles based on ultrasonic standing waves has attracted much attention for its high efficiency and simplicity of structure. This paper proposes a device that uses three modes of ultrasonic standing waves to continuously separate particles with positive acoustic contrast factor in microfluidics. Three modes of acoustic standing waves are used simultaneously in different parts of the microchannel. According to the different acoustic radiation force received by the particles, the particles are finally separated to the pressure node lines on both sides and the center of the microchannel. In this separation method, initial hydrodynamic focusing and satisfying various equilibrium constraints during the separation process are the key. Through numerical simulation, the resonance frequency of the interdigital transducer, the distribution of sound pressure in the liquid, and the relationship between the interdigital electrode voltage and the output sound pressure are obtained. Finally, the entire separation process in the microchannel was simulated, and the separation of the two particles was successfully achieved. This work has laid a certain theoretical foundation for the rapid diagnosis of diseases in practical applications

Study aspect ratio of microchannel on different polymer substrates with CO2 laser and hot bonding for microfluidic chip

The paper demonstrates four different polymer substrates including Polymethyl-methacrylate (PMMA), Polycarbonate (PC), Polystyene (PS) and Polyethylene Terephthalate (PET) for fabricating microfluidic chips using CO2 laser and hot bonding machine. The experimental methods are very simple and convenient. The work aims to obtain combination of optimal polymer for hot bonding through comparing the influence of different polymer cover plates on aspect ratio of different polymer microchannels at the same hot bonding parameters. There are three microchannels in each polymer substrate. And three microchannels are processed at three different laser parameters. The hot bonding parameters include bonding temperature of 95°C, pressure of 1Mpa for time of 9min. The results show PS cover plate with the basic plate of other substrates is the best due to stability of microfluidic chip and the ignored microchannel deformation. Next, a fluid mixing experiment in microfluidic chip with PMMA basic plate and PS cover plate is successfully performed. The microchannel in PMMA is processed with laser speed of 10mm/s, laser power of 12W, distance between the sheet surface and the lens of 7.5mm

Nonlinear macromodel based on Krylov subspace for micromixer of the microfluidic chip

The simulation of MEMS (Micro-Electro-Mechanical-System) containing fluid field could not be well performed by conventional numerical analysis methods. The micro flow field characteristics can be simulated by using macromodel including a nonlinear analysis. This paper set up the macromodel of the micromixer of the microfluidic chip using Krylov subspace projection method. The system functions were assembled through finite element analysis using COMSOL. We took the flow field-concentration field analysis for micromixer finite element model. The finite element functions order is reduced by second-order Krylov subspace projection method based on Lanczos algorithm. It can be shown that the simulation results obtained by using the macromodel are highly consistent with the results of finite element analysis. The calculation using the macromodel is two orders of magnitude faster than the calculation performed by the finite element analysis method. This macromodel should facilitate the design of microfluidic devices with sophisticated channel networks