title: 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 laminar-flow 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 × 125-μm(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.
authors.affiliation: NRC Research Associate at Naval Research Laboratory, Chemistry Division, Washington, DC 20375, USA ; Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Kennedy
authors.affiliation: Naval Research Laboratory, Chemistry Division, Washington, DC 20375, USA.
authors.forename: Harold D
authors.initials: HD
authors.lastname: Ladouceur
authors.affiliation: Department of Food Science, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Moeller
authors.affiliation: Department of Biomedical Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Dickson
authors.initials: D
authors.lastname: Kirui
authors.affiliation: Department of Food Science, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Carl A
authors.initials: CA
authors.lastname: Batt