Massive improvements in the thermophysical properties of nanofluids over conventional fluids have led to the rapid evolution of using multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) in the field of heat transfer. In this study, the heat transfer and entropy generation abilities of MWCNTs/GNPs hybrid nanofluids were explored. Experiments on forced convective flow through a brass microtube with 300 μm inner diameter and 0.27 m in length were performed under uniform heat flux. MWCNTs/GNPs hybrid nanofluids were developed by adding 0.035 wt.% GNPs to MWCNTs water-based nanofluids with mass fractions of 0.075-0.125 wt.%. The range of the Reynolds number in this experiment was maintained at Re = 200-500. Results showed that the conventional approach for predicting the heat transfer coeffcient was applicable for microtubes. The heat transfer coeffcient increased markedly with the use of MWCNTs and MWCNTs/GNPs nanofluids, with increased pressure dropping by 12.4%. Results further showed a reduction by 37.5% in the total entropy generation rate in microtubes for hybrid nanofluids. Overall, MWCNTs/GNPs hybrid nanofluids can be used as alternative fluids in cooling systems for thermal applications.

At the crossroads of chemistry, electronics, mechanical engineering, polymer science, biology, tissue engineering, computer science, and materials science, electrical devices are currently being engineered that blend directly within organs and tissues. These sophisticated devices are mediators, recorders, and stimulators of electricity with the capacity to monitor important electrophysiological events, replace disabled body parts, or even stimulate tissues to overcome their current limitations. They are therefore capable of leading humanity forward into the age of cyborgs, a time in which human biology can be hacked at will to yield beings with abilities beyond their natural capabilities. The resulting advances have been made possible by the emergence of conformal and soft electronic materials that can readily integrate with the curvilinear, dynamic, delicate, and flexible human body. This article discusses the recent rapid pace of development in the field of cybernetics with special emphasis on the important role that flexible and electrically active materials have played therein.

The wide-spread adoption of solar thermal absorbers is currently hampered by their low absorption efficiencies and their high capital cost. As a result, a number of initiatives, including direct absorption solar collectors (DASC), are currently underway to improve the absorber efficiencies. In this regard, this study focused on application of hybrid nanofluids containing reduced graphene oxides decorated with silver nanoparticles in volumetric solar absorbers. Their superior solar absorptance and thermal conductivity is based on the plasmonic effect of the nanoparticles and high thermal conductivity of graphene nanosheets, respectively. Several parameters such as mass concentration of graphene nanosheets and Ag decoration contents were studied that could affect the thermal and optical properties of the nanofluids. The results indicated that the prepared nanofluids can be employed for direct absorption solar collectors over a short period of solar irradiation time, even at a low illumination intensity of one sun. A collector efficiency of 77% is achievable at low concentration of 40 ppm owing to the enhanced light absorption of graphene at the excitation wavelength. These findings therefore suggest that this solution can contribute to the final goal of utilizing nanofluids for efficient solar thermal energy harvesting.

In this study, activated carbon (AC) was synthesized by chemical activation process from rice husk, with the BET surface area of 2180 m²/g. Chitosan/poly(ethylene oxide) (PEO)/AC nanofibrous membrane (CPANM) was synthesized by electrospinning process. The average fiber diameter was found to be 83 ± 12.5 nm. Incorporation of AC lead to increase in the surface area of CPANM than chitosan/PEO fiber (CPF) by 371 m²/g. X-ray photoelectron spectroscopy survey and narrow scan analysis further proved the presence of AC in the membrane. CPANM showed higher adsorption capability than CPF. Analysis of the mechanism of heavy metals adsorption by CPANM and CPF hypothesized that, (NH2) is the only active group in CPF, whereas both (NH2) and (COOH) contributed in adsorption for CPANM. Maximum adsorption capacity of CPANM for Cr(VI), Fe(III), Cu(II), Zn(II), and Pb(II) ion was found to be 261.1, 217.4, 195.3, 186.2, and 176.9 mg g⁻¹ respectively.

Tissue engineering aims to generate or facilitate regrowth or healing of damaged tissues by applying a combination of biomaterials, cells, and bioactive signaling molecules. In this regard, growth factors clearly play important roles in regulating cellular fate. However, uncontrolled release of growth factors has been demonstrated to produce severe side effects on the surrounding tissues. In this study, poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) incorporated three-dimensional (3D) CORAGRAF scaffolds were engineered to achieve controlled release of platelet-derived growth factor-BB (PDGF-BB) for the differentiation of stem cells within the 3D polymer network. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and microtomography were applied to characterize the fabricated scaffolds. In vitro study revealed that the CORAGRAF-PLGA-PDGF-BB scaffold system enhanced the release of PDGF-BB for the regulation of cell behavior. Stromal cell attachment, viability, release of osteogenic differentiation markers such as osteocalcin, and upregulation of osteogenic gene expression exhibited positive response. Overall, the developed scaffold system was noted to support rapid cell expansion and differentiation of stromal cells into osteogenic cells in vitro for bone tissue engineering applications.

This research explores the use of simultaneous heating and pressing techniques in order to enhance the mechanical properties of fly ash (FA) based geopolymer under relatively low temperature conditions to ensure minimum-porosity. Four effective parameters of pressing force, alkali activator/FA, duration of hot-pressing and sodium concentration are studied. Together with detailed experimental studies, our results reveal that the most dominant factor is the induced pressure. The main results indicated that the highest compressive strength of the geopolymer (134 MPa) could be obtained by employing the hot pressing, temperature and duration of 41.4 MPa, 350 °C and 20 min, respectively. The microstructure of the hot-pressed specimens showed more developed geopolymer matrix compared with conventional ones leading to higher compressive strength in much shortest time. The improved mechanical properties are generally attributed to the dense structure of the material and higher geopolymer gel production during the hot pressing process. However, further reaction of partially reacted particles improves the mechanical properties over time.

The development of new classes of fluids with enhanced heat transfer capabilities has been the subject of significant contemporary research. One area of interest in this field involves the use of nanomaterials to improve the properties of heat-transfer fluids. This research experimentally investigates promising hybrid nanofluids that contain graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs). The present article reports thermophysical properties, heat transfer coefficient, and pressure drop for MWCNTs/GNPs water based hybrid nanofluids that flow through a circular tube (D_in = 1.1 mm). The flow was assumed as a fully laminar flow (Re = 200–500), and a uniform heat flux was applied to the tube surface. Different weight concentrations of MWCNTs/water nanofluids (0.075, 0.125, and 0.25 wt%) were used and mixed with (0.035 wt%) GNPs to prepare hybrid nanofluids. Heat transfer coefficient was significantly enhanced using MWCNTs and MWCNTs/GNPs hybrid nanofluids. The enhancement of heat transfer coefficient is found to be proportionally dependent on the nanoparticle concentrations and inversely related with the Reynolds number. The positive effect of adding GNPs to different concentrations of MWCNTs enhanced the heat transfer coefficient. The maximum enhancement was recorded for 0.25 MWCNTs/0.035 GNPs hybrid at Re = 200 for a 43.4% increase with an 11% rise in pressure drop.

Recently, it has been observed that the use of magnetic nanoparticles and the magnetic field would result in heat and mass transfer intensification. But most of the investigations have been devoted to the enhancement of heat transfer. However, the investigations on the applicability of magnetic nanoparticles for mass transfer improvement are still in the developing stage. In the present study, the effect of MnFe₂O₄ nanoparticles on the mass transfer performance of a packed extraction column is evaluated in the presence of constant and alternating magnetic fields. The column is filled with Penta-Pak TM PS-500M1 structured packing; while four identical bar electromagnets made from zinc ferrite cores are used to generate the quadrupole magnetic field. The (toluene-acetic acid)-water system is employed. Spinel-type manganese ferrite nanoparticles are added to the organic dispersed phase (toluene + acetic acid) to intensify solute transfer. The quadrupole magnetic field is applied from 100 to 500 G intensity and 100 to 500 Hz frequency, accompanied with different nanoparticle concentrations from 0.001 wt% to 0.005 wt%. According to our observations, mass transfer performance increases remarkably in the presence of magnetic nanoparticles under the influence of magnetic field. Compared with no magnetic field, maximum improvements of 115% and 43% in overall mass transfer coefficient and extraction fraction are observed under alternating magnetic field with 300 Hz frequency and 500 G intensity for 0.003 wt% nanoparticle concentration. That is, by using the magnetic nanoparticles and the magnetic field, one can considerably improve the performance of a liquid-liquid extraction system.

In this study, the effect of graphene nanoplatelets (GNP)/distilled water nanofluid on the thermal performance of evacuated tube solar collector (ETSC) water heater was experimentally investigated. The mass percentage of GNP was considered at 0.025, 0.5, 0.075 and 0.1 wt%. The physical and thermal properties of the GNP nanofluids including stability, specific heat capacity, viscosity and thermal conductivity were investigated. The thermal efficiency tests on the solar collector were carried out for varying volumetric flow rate of 0.5, 0.1, and 1.5 L/min while the ASHRAE standard 93–2003 was considered to calculate the efficiency of the collector. The results indicated that the solar collector thermal efficiency gave enhancement up to 90.7% at a flow rate of 1.5 L/min when the GNP nanofluid was used as an absorption medium. The results indicated that by increasing the mass percentage of nanoparticles, thermal energy gain also increases, reaching a higher outlet temperature of the fluid when graphene nanosheets are used.