We propose an innovative mechanism for enhancing mixing in steady pressure driven flow of an electrolytic solution in a straight rectangular microchannel. A transverse electric field is used to generate an electroosmotic flow across the cross-section. The resulting flow field consists of a pair of helical vortices that transport fluid elements along the channel. We show, through numerical simulations, that chaotic advection may be induced by periodically varying the direction of the applied electric field along the channel length. This periodic electric field generates a longitudinally varying, three-dimensional steady flow, such that the streamlines in the first half of the repeating unit cell intersect those in the second half, when projected onto the cross-section. Mixing is qualitatively characterized by tracking passive particles and obtaining Poincaré maps. For quantification of the extent of mixing, Shannon entropy is calculated using particle advection of a binary mixture. The convection diffusion equation is also used to track the evolution of a scalar species and quantify the mixing efficiency as a function of the Péclet number.
A novel class of biomimetic hydroxyapatite (HAP), poly(vinyl alcohol) (PVA) and silver nanoparticles (AgNPs) impregnated soy protein isolate (SPI)-ternary and quaternary nanocomposites were fabricated by an environmentally benign hydrothermal precipitation process under UV irradiation. Various physico-chemical and mechanical characteristics showed improved mechanical properties that open up newer vistas in biomedical applications, especially for dental implantations and repairs. The SEM, FT-IR, powder-XRD, particle size distribution analysis, TG-DTA, and DSC results confirmed the complete miscibility of soy protein isolate, hydroxyapatite and poly(vinyl alcohol) through one another by strong hydrogen bonding and silver nanoparticles were evenly distributed into nano-matrix and are stable without any aggregation. The mechanical properties (tensile strength), water absorption test and in vitro antibacterial studies confirmed that soy protein isolate based composites have enough mechanical stability, low water absorption and low bacterial adhesion. The incorporation of poly(vinyl alcohol) as neutral fillers boosts the tensile strength. The TG-DTA and DSC studies envisaged better miscibility and morphological changes of hydroxyapatite, poly(vinyl alcohol) and silver nanoparticles impregnated soy protein isolate with one another with an induced thermal stability. This novel class of SPI/HAP/PVA/Ag nanocomposites shall be a potential alternative class of materials for teeth and bone, orthopaedic dental implant due to their chemical and biological similarity to human hard tissues.
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