Challenges in Nano and Micro Scale Science and Technology
Volume:12 Issue: 1, Winter-Spring 2024

This study explores the heat transfer (HT) characteristics of non-Newtonian fluids in hydrophobic microchannels influenced by magnetic fields (MFs). Using the Lattice Boltzmann Method (LBM), a detailed two-dimensional microscale model is developed to analyze the combined effects of flow slippage, viscous dissipation, and temperature jump phenomena. The power-law model is employed to represent the non-Newtonian fluid behavior accurately. The results demonstrate that increasing the slip length significantly enhances convective HT by modifying boundary layer dynamics. However, this enhancement is mitigated by the opposing effects of temperature jump and viscous dissipation. The introduction of a magnetic field further alters the flow dynamics, with the Lorentz force optimizing velocity profiles and substantially boosting HT efficiency. The results show that the presence of magnetic field with Ha=20 enhances heat transfer 3.3% and 4.2% at B=0 and B=0.06 respectively for non-Newtonian fluid flow with n=0.9. These findings underline the intricate interplay between magnetic field intensity, fluid rheology, and surface properties, offering valuable guidance for designing advanced thermal management systems in microchannel applications.

In recent years, there has been a growing interest in the development of eco-compatible nanomaterials in the packaging industry to reduce organic waste. One area of research is smart and biodegradable nanofilms, which hold significant potential for reducing agricultural waste and accelerating the decomposition of organic waste from agricultural products and food. In addition, the usage of nanocomposites in packaging is effective in maintaining the quality of food and its shelf life. The aim of this study is to introduce a nanocomposite film of polylactic acid (PLA)/carbopol/nanoanthocyanin to produce an innovative product in the packaging industry with biodegradable and green coatings. In this study, parameters such as oxygen permeation, turbidity, transparency, thickness, tensile strength, water absorption, and water vapor permeability of the films were evaluated. The results showed a significant difference at the 5% level in the tensile strength between the control and the biodegradable films. There was also a significant difference at the 1% level in the water absorption rate between the control and biodegradable films, with the treatment (T1) and control samples having the highest (%18.44 and %19.01), respectively, and the treatment (T4) having the lowest (%10.45). The combination of nano film PLA/carbopol/nanoanthocyanin in (T4) exhibited unique properties compared to other samples. In this film, although PLA and carbopol increased the mechanical strength of (T4), its biodegradability properties can accelerate the degradation process of the nanofilms. Consequently, the packaging coatings decompose easily without harming the environment

A vertical two-electrode polymeric nanogenerator energy harvester, utilizing KAPTON and PDMS as the positive and negative triboelectric materials, respectively, was investigated through both experimental and numerical approaches. To simulate environmental low-frequency motions, a vibrational force of 20 mN at 8 Hz was applied to the device using a custom-designed mechanical instrument. Experimental measurements confirmed the nanogenerator's ability to generate an output voltage and current with maximum amplitudes of 4 V and 0.025 μA, respectively. The charge production mechanism of the device was then modeled numerically, both with and without the inclusion of the edge-effect capacitor. The modeling results demonstrated strong agreement with experimental data, with the incorporation of the edge-effect capacitor significantly improving the alignment between calculated and observed values. The validated model provides a valuable tool for designing high-performance triboelectric nanogenerators for various applications and conditions. Additionally, further investigations into environmental influences revealed reduced device performance at lower pressures and higher temperatures.

The separation of drug enantiomers is crucial in the pharmaceutical industry, as each enantiomer can exhibit different biological activities. Modafinil is a racemic drug, with the R enantiomer being primarily responsible for its pharmacological effects. The main objective of this study was to identify a suitable carbon nanotube (CNT) structure to effectively separate the enantiomers of Modafinil.Molecular docking simulations were performed to investigate the binding of Modafinil enantiomers with various chiral CNTs (7,6), (8,7), (9,8), and (10,9) with lengths ranging from 11 to 15 Angstroms. Molecular docking simulations showed that the CNT (8,7) with a length of 15 Angstroms could effectively separate the S and R enantiomers of Modafinil. The R enantiomer was adsorbed on the surface of the CNT, with a binding energy of -3.49 kcal/mol, while the S enantiomer was located inside the nanotube, with a binding energy of -4.34 kcal/mol.Density functional theory (DFT) calculations at the B3LYP/6-31G level were then employed to optimize the structures and investigate the interactions of the drug enantiomers with the selected CNT. Density functional theory (DFT) calculations revealed that the R enantiomer had a higher binding energy compared to the S enantiomer, indicating better stability upon adsorption on the CNT surface. Further analysis of electronic properties, including frontier orbital energies, reactivity descriptors, Mulliken atomic charges, dipole moments, and molecular electrostatic potentials, provided insights into the differences in the behavior and interactions of the two Modafinil enantiomers with the CNT.

Phase change materials (PCM) can be employed in many fields due to their capacity to absorb and release energy when it is necessary. Nowadays, the number of studies about these kinds’ materials is increasing because of their benefits in the energy storage systems. In microencapsulation, the core material is defined as the specific material coated and can be in the liquid or solid state depending on the temperature. In this research, two new PCM microcapsules based on palmitic acid (PA) core and silicon dioxide (SiO2), strontium titanate (SrTiO3) were shelled and synthesized through self-method in three core/shell weight ratios (50/50, 40/60, 30/70). Finding the thermal properties of these materials experimentally, then the thermal simulation in rectangular energy storage was performed under the constant heat flux. The simulated results were analyzed and discussed. Among the synthesized microcapsules, the best results were PA@SiO2 with a weight ratio of 30/70. This sample had maximum amount of 24.42% melting time in 12,000 seconds and the maximum temperature at 369 K, which indicated 196.8% higher than the pure PA.

This study investigates the impact of magnetic hyperthermia on the treatment of peritoneal metastases and analyzes the effects of abdominal fat and tumor position. The primary objective is to assess the effectiveness of localized heating with magnetic fields in eliminating cancer cells while minimizing damage to healthy tissue. In this study, magnetic nanoparticles Fe₃O₄ were used to increase the temperature of tumor tissues to the range of 42-46 °C under the influence of an alternating magnetic field. A numerical simulation using the finite element method was conducted to analyze the impact of abdominal fat and tumor position on heat transfer, and the distribution of magnetic field intensity was calculated using Maxwell's equations and the heat generated by nanoparticles based on Rosensweig's theory. In this study, the heat generated by nanoparticles in the tumor has been incorporated into the Pennes bioheat transfer equation, and the temperature distribution in the tumor and surrounding healthy tissues has been calculated. Magnetic hyperthermia effectively eliminates cancer cells and performs well in areas with thick abdominal fat, which are challenging, so abdominal fat does not hinder hyperthermia. The tumor's position significantly affects heat distribution, and more precise adjustments are needed in areas with higher metastasis. This method can be used alone or with other treatments.