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1.
Sensors (Basel) ; 21(10)2021 May 18.
Article in English | MEDLINE | ID: mdl-34069780

ABSTRACT

The objective of the current study is to analyze numerically the effect of the temperature-jump boundary condition on heterogeneous microfluidic immunosensors under electrothermal force. A three-dimensional simulation using the finite element method on the binding reaction kinetics of C-reactive protein (CRP) was performed. The kinetic reaction rate was calculated with coupled Laplace, Navier-Stokes, energy, and mass diffusion equations. Two types of reaction surfaces were studied: one in the form of a disc surrounded by two electrodes and the other in the form of a circular ring, one electrode is located inside the ring and the other outside. The numerical results reveal that the performance of a microfluidic biosensor is enhanced by using the second design of the sensing area (circular ring) coupled with the electrothermal force. The improvement factor under the applied ac field 15 Vrms was about 1.2 for the first geometry and 3.6 for the second geometry. Furthermore, the effect of temperature jump on heat transfer rise and response time was studied. The effect of two crucial parameters, viz. Knudsen number (Kn) and thermal accommodation coefficient (σT) with and without electrothermal effect, were analyzed for the two configurations.


Subject(s)
Biosensing Techniques , Microfluidics , Hot Temperature , Immunoassay , Temperature
2.
Micromachines (Basel) ; 11(9)2020 08 31.
Article in English | MEDLINE | ID: mdl-32878031

ABSTRACT

The principal aim of this study was to analyze the effect of slip velocity at the microchannel wall on an alternating current electrothermal (ACET) flow micropump fitted with several pairs of electrodes. Using the finite element method (FEM), the coupled momentum, energy, and Poisson equations with and without slip boundary conditions have been solved to compute the velocity, temperature, and electrical field in the microchannel. The effects of the frequency and the voltage, and the electrical and thermal conductivities, respectively, of the electrolyte solution and the substrate material, have been minutely analyzed in the presence and absence of slip velocity. The slip velocity was simulated along the microchannel walls at different values of slip length. The results revealed that the slip velocity at the wall channel has a significant impact on the flow field. The existence of slip velocity at the wall increases the shear stress and therefore enhances the pumping efficiency. It was observed that higher average pumping velocity was achieved for larger slip length. When a glass substrate was used, the effect of the presence of the slip velocity was more manifest. This study shows also that the effect of slip velocity on the flow field is very important and must be taken into consideration in an ACET micropump.

3.
Int J Biol Macromol ; 147: 258-267, 2020 Mar 15.
Article in English | MEDLINE | ID: mdl-31917217

ABSTRACT

In the present study, the magnetic nanocomposite is fabricated using chitosan, thiobarbituric acid, malondialdehyde and Fe3O4 nanoparticles (CTM@Fe3O4). The fabricated nanocomposite (CTM@Fe3O4) is characterized using FTIR, TGA, BET, XRD, Raman, XPS, FESEM, and HRTEM techniques. The results of BET analysis confirmed that the nanocomposite has a mesoporous structure with high surface area of 376 m2 g-1 and high pore volume 0.3828 cm3 g-1. The adsorption of tetracycline (TC) onto CTM@Fe3O4 adsorbent is carried out using batch technique by changing several factors such as pH, concentration, contact time, and temperature. Langmuir and pseudo-second-order nonlinear models were found to be the best-fit models to predict isotherms and kinetics of adsorption, respectively. The highest adsorption capacity of 215.31mg/g was achieved at the optimum conditions of 0.05g adsorbent dosage, 60mg/L TC concentration. Overall, results demonstrated that CTM@Fe3O4 nanocomposite was an excellent adsorbent material with superparamagnetic properties, which allowed the separation as well as recovery of the adsorbent from aqueous solution using external magnet for effective industrial applications.


Subject(s)
Chitosan/chemistry , Magnetic Phenomena , Nanocomposites/chemistry , Tetracycline/isolation & purification , Adsorption , Ferric Compounds/chemistry , Hydrogen-Ion Concentration , Kinetics , Malondialdehyde/chemistry , Nitrogen/chemistry , Photoelectron Spectroscopy , Spectroscopy, Fourier Transform Infrared , Spectrum Analysis, Raman , Thermodynamics , Thiobarbituric Acid Reactive Substances/chemistry , Time Factors , X-Ray Diffraction
4.
RSC Adv ; 10(40): 23615-23623, 2020 Jun 19.
Article in English | MEDLINE | ID: mdl-35517314

ABSTRACT

The vibrational and optical properties of an La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 (LSNMT) polycrystalline sample produced via a solid-state reaction were studied. The Raman spectrum at room temperature reveals the chemical disorder in our compound. The optical gap and Urbach energy were estimated on the basis of the absorption spectrum. Moreover, the polycrystalline manganite radiates in the near-infrared light (1000 nm) with 514.5 nm light excitation and in the temperature range from 10 K to 300 K. Crystal field analysis suggests that only the Mn4+ luminescent center is found in LSNMT. The measured activation proves that our compound possesses good thermostability. The chromaticity coordinates prove that the emission of the LSNMT sample occurs in the near-infrared region. All analytical findings demonstrate that LSNMT manganite has substantial prospective applications in white luminescent devices.

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