title: Measurements of diffusion coefficients in 1-D micro- and nanochannels using shear-driven flows.
abstract: The present paper describes a method for measuring the molecular diffusion coefficient of fluorescent molecules in microfluidic systems. The proposed static shear-driven flow method allows one to perform diffusion measurements in a fast and accurate manner. The method also allows one to work in very thin (i.e. submicron) channels, hence allowing the investigation of diffusion in highly confined spaces. In the deepest investigated channels, the obtained results were comparable to the existing literature values, but when the channel size dropped below the micrometer range, a significant decrease (more than 30%) in molecular diffusivity was observed. The reduction of the diffusivity was most significant for the largest considered molecules (ssDNA oligomers with a size ranging between 25 to 100 bases), but the decrease was also observed for smaller tracer molecules (FITC). This decrease can be attributed to the interactions of the analyte molecules with the channel walls, which can no longer be neglected when the depth of the channel reaches a critical value. The change in diffusivity seems to become more explicit as the molecular weight of the analytes increases.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering Pleinlaan 2, 1050, Brussels, Belgium. kris.pappaert@vub.ac.be
authors.forename: Kris
authors.initials: K
authors.lastname: Pappaert
authors.forename: Jurgen
authors.initials: J
authors.lastname: Biesemans
authors.forename: David
authors.initials: D
authors.lastname: Clicq
authors.forename: Sarah
authors.initials: S
authors.lastname: Vankrunkelsven
authors.forename: Gert
authors.initials: G
authors.lastname: Desmet
mesh_terms: D004277:DNA, Single-Stranded / Q000737:chemistry; D004058:Diffusion; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D007700:Kinetics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D008904:Miniaturization; D008970:Molecular Weight; D036103:Nanotechnology; D009841:Oligonucleotides / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D016650:Fluorescein-5-isothiocyanate