Rheological and flow birefringence studies of rod-shaped pigment nanoparticle dispersions

The flow of anisotropic nanoparticles in solution and in blood

The alignment of anisotropic nanoparticles in flow has been used for a range of applications such as the preparation of strong fibres and the assembly of in-plane aligned 1D-nanoobjects that are used for electronic devices, sensors, energy and biological application. Important is also the flow behaviour of nanoparticles that were designed for nanomedical applications such as drug delivery. It is widely observed that non-spherical nanoparticles have longer circulation times and a more favourable biodistribution. To be able to understand this behaviour, researchers have turned to analyzing the flow of non-spherical nanoparticles in the blood stream. In this review, an overview of microfluidic techniques that are used to monitor the alignment of anisotropic nanoparticles in solution will be provided, which includes analysis by small angle X-ray scattering (SAXS) and polarized light microscopy. The flow of these nanoparticles in blood is then discussed as the presence of red blood cells causes margination of some nanoparticles. Using fluorescence microscopy, the extent of margination can be identified, which coincides with the ability of nanoparticles to adhere to the cells grown along the wall. While these studies are mainly carried out in vitro using blood, initial investigations in vivo were able to confirm the unusual flow of anisotropic nanoparticles.

Shear-induced birefringence in an optically isotropic cubic liquid crystalline phase

We report an unusually strong flow-induced birefringence in an optically isotropic cubic phase occurring below the isotropic chiral conglomerate phase formed by a low-molecular-weight polycatenar mesogen. The transition into the birefringent state occurs thresholdless and the induced birefringence is comparable with that observed in polymeric systems. We suggest that the flow-induced deformation of the cubic structure is responsible for the strong rheo-optical response.

Marangoni Convection of Dust Particles in the Boundary Layer of Maxwell Nanofluids with Varying Surface Tension and Viscosity

The flow of nanofluids is very important in industrial refrigeration systems. The operation of nuclear reactors and the cooling of the entire installation to improve safety and economics are entirely dependent on the application of nanofluids in water. Therefore, a model of Maxwell’s dusty nanofluid with temperature-dependent viscosity, surface suction and variable surface tension under the action of solar radiation is established. The basic equations of momentum and temperature of the dust and liquid phases are solved numerically using the MATLAB bvp4c scheme. In the current evaluation, taking into account variable surface tension and varying viscosity, the effect of dust particles is studied by immersing dust particles in a nanofluid. Qualitative and quantitative discussions are provided to focus on the effect of physical parameters on mass and heat transfer. The propagation results show that this mixing effect can significantly increase the thermal conductivity of nanofluids. With small changes in the surface tension parameters, a stronger drop in the temperature distribution is observed. The suction can significantly reduce the temperature distribution of the liquid and dust phases. The stretchability of the sheet is more conducive to temperature rise. The tables are used to explain how physical parameters affect the Nusselt number and mass transfer. The increased interaction of the liquid with nanoparticles or dust particles is intended to improve the Nusselt number. This model contains features that have not been previously studied, which stimulates demand for this model among all walks of life now and in the future.

Chitin nanocrystals based complex fluids: A green nanotechnology

Chitin biopolymer has received significant attention recently by many industries as a green technology. Nanotechnology has been used to make chitin nanocrystals (ChiNCs) that are rod-shaped natural nanomaterials with nanoscale size. Owing to the unique features such as biodegradability, biocompatibility, renewability, rod-shape, and excellent surface and interfacial, physiochemical, and thermo-mechanical properties; ChiNCs have been green and attractive products with wide applications specifically in medical and pharmaceutical, food and packaging, cosmetic, electrical, and electronic, and also in the oil and gas industry. This review aims to give a comprehensive and applied insight into ChiNCs technology. It starts with reviewing different sources of chitin and their extraction methods followed by the characterization of ChiNCs. Furthermore, a detailed investigation into various complex fluids (dispersions, emulsions, foams, and gels) stabilized by ChiNCs and their characterisation have been thoroughly deliberated. Finally, the current status including ground-breaking applications, untapped investigations, and future prospective have been presented.