Analysis of a laminar-flow diffusional mixer for directed self-assembly of liposomes

Abstract

The present work describes the operation and simulation of a microfluidic laminarflow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 Â 125-lm 2 cross-section. Use of the device produces liposomes in the size range of 100-300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using COMSOL Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein.

Microfluidic hydrodynamic focusing for synthesis of nanomaterials

“…Later, they demonstrated controllable drug loading into the synthesized liposomes in continuous flow mode [51,54]. Kennedy et al used a 3D HF device in order to synthesize liposomes in the size range of 100–300 nm by changing sheath-to-core flow ratio, and concentrations of lipids and salts in the core and sheath flows, respectively [88]. The further study by Phapal et al showed that, in 3D HF devices, the size distribution of liposomes is strongly affected in the convective mixing regime at high Peclet number (Pe≫1) [89].…”

“…(a) [88] (Printed with permission from AIP Publishing LLC) and (b) [58] (Printed with permission from IOP Publishing) shows examples of two layer on-chip 3D HF devices utilizing height variations to generate 3D-layered flow structures.…”

Numerical study of the effects of internal and external forces on the nanoparticle mixing in a ferrofluid flow

“…Mixers in microfluidics can be classified into groups of passive and active, where the second type needs an external energy supply . Forces resulting from acoustic, dielectrophoretic, electromagnetic, electrohydrodynamic, temperature gradient, and pressure perturbations are examples of external energies used to improve mixing in active mixers …”

“…Mixers in microfluidics can be classified into groups of passive and active, where the second type needs an external energy supply. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Forces resulting from acoustic, dielectrophoretic, electromagnetic, electrohydrodynamic, temperature gradient, and pressure perturbations are examples of external energies used to improve mixing in active mixers. 17 El Moctar et al 18 studied a micromixer in which two fluids with identical viscosity and density, but different electrical properties, were injected by syringe pumps.…”

Particle-Based Monte-Carlo Simulations of Steady-State Mass Transport at Intermediate Péclet Numbers

“…Exact results for advection coupled to diffusion are also known for certain geometries, notably in the case of Taylor dispersion [7]. In general, however, for predicting the steady-state distributions of particles in the presence of diffusion in arbitrary geometries, conventional strategies rely on solving the continuity equation in three dimensions [8][9][10].…”