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To combat the coronavirus disease 2019 (COVID-19), great efforts have been made by scientists around the world to improve the performance of detection devices so that they can efficiently and quickly detect the virus responsible for this disease. In this context we performed 2D finite element simulation on the kinetics of SARS-CoV-2 S protein binding reaction of a biosensor using the alternating current electrothermal (ACET) effect. The ACET flow can produce vortex patterns, thereby improving the transportation of the target analyte to the binding surface and thus enhancing the performance of the biosensor. Optimization of some design parameters concerning the microchannel height and the reaction surface, such as its length as well as its position on the top wall of the microchannel, in order to improve the biosensor efficiency, was studied. The results revealed that the detection time can be improved by 55% with an applied voltage of 10

In this chapter, we investigated the effect of geometric parameters of the nozzle orifice on cavitating flow and entropy production in a diesel injector. Firstly, we analyzed the effect of some parameters of diesel injector such as the nozzle length and the lip rounding on cavitating flow. In the second parts, we studied the entropy production inside the diesel injector in several cases: -single phase and laminar flow,- single phase and turbulent flow and –tubulent cavitating flow. In the last case, the mixture model cupled with k-ε turbulent model has been adopted. The effects of average inlet velocity and cavitation number on entropy production have been presented and discussed. The results obtained show that the discharge coefficient is weakly influenced by the length of the orifice and the radius of the wedge has a large effect on the intensity and distribution of cavitation along the injection nozzle. On the other hand, the study of entropy production inside the diesel injector shows that the entropy production is important near the wall and increases whith increasing the average inlet velocity and pressure injection.

The main objective of this work is to study the transient Joule heating effect in a conductive-bridge random-access memory (CBRAM) using the single-phase-lag heat conduction model to describe the effects of the metallic conductive filament (CF) radius and the reset voltage on the thermal and electric field. The results reveal that the CF geometry plays an important role in the transient Joule heating. The heat wave of fast transient conduction is stronger in the narrow region of the CF during the reset process for a high applied voltage and a small top radius of the CF. It is demonstrated that the presented model can predict the nanoscale heat transfer in the transient state and during the reset process in the CBRAM. Finally, numerical computations are carried out using the finite-element method to solve the nonlinear heat conduction equations.

The objective of the present study is to analyze the heat transfer in the gate-all-around (GAA) MOSFETs based on the Cattaneo and Vernotte (CV) model due to the finite heat propagation speed in these nanodevices. The derivation of the CV model from the Boltzmann transport equation (BTE) is presented. Using the finite-element method, the nonlinear heat conduction model coupled with Poisson and continuity equations has been numerically solved to predict the self-heating effect (SHE) in GAA MOSFET. The CV model is applied in several structures, namely, single-metal surrounding gate (SMSG), dual-metal surrounding gate (DMSG), and triple-metal surrounding gate (TMSG). The obtained results are also compared with those calculated with the Fourier law. The temporal evolution and spatial distribution of the temperature and heat flux have been investigated. It is seen that the oscillatory behavior of the temperature using the CV model is strengthened for the TMSG structure and by increasing the relaxation time. Furthermore, the TMSG structure leads to an important increase in the temperature inside the device.

In this article, we propose a 2-D study for investigating the self-heating effect in new partially insulated field-effect transistors (PiFETs) based on high- ${k}$ gate dielectrics. The thermal properties have been numerically simulated and compared to those of conventional bulk-metal–oxide–semiconductor field-effect transistor (bulk-MOSFET) and PiFET structures. Several high- ${k}$ materials such as ZrO2, HfO2, La2O3, and Al2O3 are used in order to test their impact on the temperature rise in the host lattice of new structures. A deal of interest has been paid to geometric parameters in the PiFET structures studied to further reduce the self-heating. The effects of geometrical and electrical parameters have been analyzed. As it is found, a significant reduction in temperature rise is achieved during high-power operation. This suggests that the insertion of high- ${k}$ dielectric layers above the dioxide can mitigate the self-heating. More especially, Al2O3 has been revealed as an appropriate high- ${k}$ dielectric to being recommended for the production of high-performance PiFET.

A numerical study of the phonon scattering effect in Gate All Around Field Effect Transistor (GAAFET) is performed in this work. The self-heating is modeled based on the Dual-Phase Lag (DPL) heat conduction equation. Poisson and drift-diffusion equations for electron and hole coupled with DPL model have been investigated based on the finite element method. Numerical solutions are obtained using the technique of nonlinear Newton–Raphson iteration. The impact of dependent-temperature (TD) parameters such as thermal conductivity, heat flux phase lag, and volumetric heat capacity on temperature distribution is taken into consideration. Further, a temperature jump boundary condition is used at semiconductor-oxide interface to take into account the phonon scattering phenomenon. Obtained results show a decrease in temporal and spatial temperature distribution in the case of using (TD) parameters compared with the constant (CST). Also, the addition of jump boundary condition causes a reduction on the maximum temperature and heat flux. Thus, the DPL model with proposed TD parameters, including jump temperature boundary condition, is recommended for the investigation of the self-heating effect, which can provide some improvement for the development GAAFET with good reliability in the device.

In this research, Taguchi's method was employed to optimize the performance of a microfluidic biosensor with an integrated flow confinement for rapid detection of the SARS-CoV-2. The finite element method was used to solve the physical model which has been first validated by comparison with experimental results. The novelty of this study is the use of the Taguchi approach in the optimization analysis. An

The aim of the present work is to investigate numerically the self-heating effect (SHE) in MOSFET transistors based on high-k material taking into account the deformation of the gate under the SHE. The SHE inside the MOSFET transistor is calculated using the electrothermal model based on heat transfer equation coupled with semiconductor equations. The electrothermal model have been solved in 2D-dimension using the finite element method. The high-k dielectric HfO2 have been used as gate oxide. Several gate shapes have been used to analyze their impact on SHE. It is observed that the reduction of equivalent oxide thickness (EOT) reduces the SHE in the MOSFET transistor based in high-k dielectric material. the temperature peak increases quadratically with drain voltage for all MOSFET structures. A decrease in self-heating effect is achieved using the square gate shape.

Modern transistors such as FinFETs and GAAFET suffer from excessive heat confinement due to their small size with limited paths to the thermal ambient. This, results in device self-heating, which can reduce speed, increase leakage, and accelerate aging. In this paper, we present a comparison of the temperature distribution in nanosized FinFET, one-nanowire Gate-All-Around FET (1N-GAAFET) and in two-nanowire Gate-All-Around FET (2N-GAAFET) structures. Two different heat transfer models are taken into considerations. The first one is the classical Fourier-Kirchhoff model, while the second one is called the Single-Phase-Lag model. The numerical simulation has been investigated using finite element method.

The self-heating effect in gate all around FET transistors (GAAFET) is investigated in this paper. The finite element method is used to analyze the heat conduction based on the 2d single-phase lag (SPL) equation. New devices with linear doping profile in the source and drain region have been taken into consideration. The study has carried out different structures, triple material surrounding gate (TMSG), dual material surrounding gate (DMSG), and single material surrounding gate (SMSG) structure. The simulation results were compared to conventional devices with a constant doping profile. The influence of heat flux time lag values in temperature distribution has also been discussed. Results show that the linear doping profile and the right choice of the gate work function or the heat flux lag $\tau\mathrm{q}$ parameters provide better energy management profile to improve performance of technology applications

In this paper, we study the AC electrothermal (ACET) effect on the binding reaction of immunoassays which a ligand (anti-C-reactive protein) immobilized on a microchannel wall specifically binds analyte (C-reactive protein (CRP)) flowing through a configuration of a microchannel with asymmetrical planar electrode pairs. The Navier–Stokes equations coupled with the Laplace and energy equations, the Fick’s second law in convection–diffusion coupled with the first order Langmuir adsorption model are used. The set of equations is solved in a two-dimensional configuration using the finite element method. Three cases of the thermal boundary conditions are investigated to study the effect of the temperature field on the binding reaction efficiency. The electrical conductivity of the buffer solution, the thermal conductivity of the base material and the surface reaction length are also discussed in this work. The simulation results show that the heterogeneous immunoassay is improved when the external surfaces of the cover and the substrate are kept at a constant temperature. For the best case studied in this work, the enhancement factors of the binding curve can be raised up to 3.46 and 2.84 for the association and dissociation phases, respectively, with 4 Vrms applied voltage and operating frequency of 100 kHz and electrical conductivity of 0.01 S/m.

In the present work, a one dimensional numerical study of nanoheat transfer in Metal / Oxide / Semiconductor / Field Effect Transistors (MOSFET) structures has been investigated. Several heat conduction models, such as Fourier, Single Phase lag (SPL) and Double Phase Lag (DPL) models, are developed and solved numerically using finite difference method. The numerical results calculated with our Matlab code are compared with those available in literature. A simulation of characteristic parameter's effect of DPL equation particularly the Knudsen number and time on local maximum temperature is discussed. The effect of the temperature-jump boundary condition is also used in order to consider the boundary phonon scattering at nanoscale. The effect of adding a layer of high-k material between the gate and the silicon leads to a considerable improvement in the temperature performance compared to that in conventional MOSFET transistors. The presented data of simulation are useful in designing the nano-transistor in order to reduce the self heating effect.

In the present work, the nonequilibrium entropy production under the effect of the dual-phase-lag heat conduction model in a two-dimensional sub-100 nm metal-oxide-semiconductor field-effect transistor (MOSFET) has been investigated. A nanoscale heat source term and different boundary conditions are included and compares the simulation results with those obtained from the phonon Boltzmann transport equation (BTE) and the Fourier law. The transient Dual-phase lag (DPL) model is solved using finite-element scheme for space and semi-implicit finite-difference for time. The effect of the Knudsen number in local entropy production is investigated. Also, the difference between the equilibrium and the nonequilibrium under the effect of the dual-phase-lag heat conduction model is studied. It is shown that the entropy production cannot be described using the classical form of the equilibrium entropy production for a high Knudsen number and in transient state. It was found that transient entropy generation obtained by the DPL model exhibits an oscillatory behavior for MOSFET with internal heat generation.

This paper aims to enhance the analyte transport toward the sensing area and to enhance biosensors performances. A microchannel-based flow confinement method for rapid delivery of small sample volumes to sensor surface is described. To confine the flow, a sample flow is joined with a perpendicular makeup flow and is confined into a thin layer above the reaction surface. The numerical simulation of the confinement effect on the binding reaction is performed using the finite-element method. The influence of several parameters on the binding reaction is provided, such as the average flow velocity at the inlet of the microchannel and the velocity of the confinement flow, the characteristics of the flow confinement. The numerical results reveal that the flow confinement enhances mass transport of analytes and increase its velocity. The obtained results could be exploited in flow injection experiments for low volume.

This paper investigates the effect of temperature-jump boundary condition on nonequilibrium entropy production under the effect of the dual-phase-lagging (DPL) heat conduction model in a two-dimensional sub-100 nm metal-oxide-semiconductor field effect transistor (MOSFET). The transient DPL model is solved using finite element method. Also, the influences of the governing parameters on global entropy generation for the following cases—(I) constant applied temperature, (II) temperature-jump boundary condition, and (III) a realistic MOSFET with volumetric heat source and adiabatic boundaries—are discussed in detail and depicted graphically. The analysis of our results indicates that entropy generation minimization within a MOSFET can be achieved by using temperature-jump boundary condition and for low values of Knudsen number. A significant reduction of the order of 85% of total entropy production is observed when a temperature-jump boundary condition is adopted.

This paper presents a COMSOL Multiphysics 2-D axisymmetric model of a pH-sensitive electrochemical field effect transistor (pH-ElecFET) microsensor. This device combines an integrated microelectrode with a pH-sensitive chemical field effect transistor (pH-ChemFET). Thus, by triggering electrolysis phenomena owing to the integrated microelectrode, associated local pH variations in microvolumes are monitored thanks to the pH-ChemFET microdevice. Taking into account (electro) chemical reactions and diffusion phenomena in the liquid phase, the proposed model points out the role of the ElecFET geometrical design (microelectrode width $w$ , gate sensitive radius $r_{e}$ and distance between the pH-ChemFET gate and the microelectrode $d$ ), as well as polarization parameters, (polarization voltage $V_{p}$ and time $t_{p})$ , on the microsensor response. It is first applied to water electrolysis in order to validate pH impulsional variations in microvolume. Then, the oxidation of hydrogen peroxide in phosphate buffer (PBS, pH0 = 7.2) solutions is studied, evidencing the H2O2 potentiometric detection in the [10–100 mM] concentration range. This developed model paves new ways for sensor applications, opening several new opportunities for pH-ElecFET devices for H2O2-related enzymatic detection of biomolecules.

Fluid deformations around a cylinder combined with an applied electric field are used to enhance the kinetics rate and the response time of heterogeneous immunosensors in microfluidic systems. The insertion of an obstacle in the microchannel as well as the application an applied electric field are used to change the fluid motion topology that improves the transport of diffusion-limited proteins. The response time is affected by various parameters such as the inlet flow velocity, the initial analyte concentration and the obstacle position. The effects of the parameters related to the kinetics reaction on the sensitivity and the performance of the biosensor have been studied numerically. Numerical results reveal that an appropriate choice of the inlet analyte and inlet flow velocity with applied electric field may reduce considerably the response time and enhance the microfluidic sensor performance.

Hydrodynamic cavitation has an important effect on the performance of Diesel injectors. It influences the nature of the fuel spray and the efficiency of the combustion process. In the present study, we investigate numerically the effect of wall roughness in the cavitating and turbulent flow developing inside a Diesel injector. The mixture model based on a single fluid is adopted and the commercial Fluent software is used to solve the transport equations. The discharge coefficient Cd is computed for different cavitation numbers and wall roughness heights. Profiles of density mixture, vapor volume fraction, mean velocity and turbulent kinetic energy are reported. The effects of wall roughness and injection pressure are analyzed.

International audience; The present work reports on a theoretical study of spontaneous and piezoelectric polarization effects on the photovoltaic characteristics of InGaN/GaN multiple quantum well solar cells. More especially, it will prove that the use of heterostructures with N-face as a surface polarity can further improve the photovoltaic conversion. A new model including piezoelectric polarization is developed. In this paper, a part of simulation is also paid to analyze the dependence of the photocurrent density, the open circuit voltage, the output power and the efficiency versus the In composition and the number of quantum well units. As has been found, a maximum of energy conversion is expected to achieve 19 percent for optimum alloy composition. An attempt to explain the photovoltaic behavior of the solar cells in correlation of obtained results will be attempted.

Binding reaction is a natural characteristic that is applied to design biosensors. In this study we simulate the binding reaction kinetics between the immobilized antibody and the targeted antigen in a reaction chamber (microchannel) of a biosensor under AC applied electric field. The diffusion boundary layer on the sensitive area of the biosensor would hinder the binding reaction from association and dissociation. We studied the influence of the shape and position of reaction surface under AC applied voltage on the binding reaction. The electrothermal force, produced by the AC electric field can induce a pair of vortices to stir the flow field over the reacting surface allowing accelerate the binding reaction. Our approach may contribute to efficient development and optimization of a biosensor for medical applications.

The flow inside Diesel injectors is important because of its effect on the spray and the atomization process in the combustion chamber. Due to huge stress at the orifice entrance, cavitation occurs in high-pressure Diesel injectors. In this study, we investigate numerically the cavitating steady flow in a Diesel injector. The mixture model based on a single fluid and the standard k-e turbulence model are used to simulate the multiphase turbulent flow. The effects of some geometrical parameters on both the discharge coefficient and the vapor fraction are presented.