Gravity-induced swirl of nanoparticles in microfluidics

Abstract

Parallel flows of two fluids in microfluidic devices are used for miniaturized chemistry, physics, biology and bioengineering studies, and the streams are often considered to remain parallel. However, as the two fluids do not always have the same density, interface reorientation induced by density stratification is unavoidable. In this paper, flow characteristics of an aqueous polystyrene nanofluid and a sucrose-densified aqueous solution flowing parallel in microchannels are examined. Nanoparticles 100 nm in diameter are used in the study. The motion of the nanoparticles is simulated using the Lagrangian description and directly observed by a confocal microscope. Matched results are obtained from computational and empirical analysis. Although solution density homogenizes rapidly resulting from a fast diffusion of sucrose in water, the nanofluid is observed to rotate for an extended period. Angular displacement of the nanofluid depends on the ratio of gravitational force to viscous force, Re/Fr2, where Re is the Reynolds number and Fr is the Froude number. In the developing region at the steady state, the angular displacement is related to y/Dh, the ratio between distance from the inlet and the hydraulic diameter of the microfluidic channel. The development of nanofluid flow feature also depends on h/w, the ratio of microfluidic channel’s height to width. The quantitative description of the angular displacement of nanofluid will aid rational designs of microfluidic devices utilizing multistream, multiphase flows.

Measuring the Soret coefficient of nanoparticles in a dilute suspension

“…The transport of species model was modified to include the thermophoretic flux term D T c ∇ T (Duhr and Braun 2006a) and solved together with laminar flow and heat transfer models. For discrete phase model, ANSYS Fluent (Canonsburg, PA) was employed to simulate heat transfer, laminar flow, and particle tracking in 3D (Zhao et al 2013). Nanoparticles with a diameter of 100 nm were randomly injected in the 3D microfluidic chamber.…”

Receptors Implicated in Microgravity-Induced Bone Loss

“…Gravity produces forces that profoundly affect fluids on Earth [191,192]. Since human beings are typically 55-70% water [193], it is not surprising that low gravity experienced by space travelers affects their cardiovascular system, lymphatic system, interstitial fluid distribution, and even the fluid distribution inside cells.…”

Nanotherapeutic Heterogeneity: Sources, Effects, and Solutions

“…[38,[103][104][105][106] Nonetheless, the kinetics of solvent mix-ing and diffusion lead to imperfect mixing of solvents and nanotherapeutic components. [96,[107][108][109] We have studied this by using a microfluidic herringbone mixer to create nanoemulsions loaded with a Förster resonance energy transfer (FRET) pair (Figure 3f). [96] Prior to nanoparticle formation, the FRET donor and acceptor were not in close proximity, resulting in green light emission.…”