title: Lateral migration and focusing of colloidal particles and DNA molecules under viscoelastic flow.
abstract: Much difficulty has been encountered in manipulating small-scale materials, such as submicron colloidal particles and macromolecules (e.g., DNA and proteins), in microfluidic devices since diffusion processes due to thermal (Brownian) motion become more pronounced with decreasing particle size. Here, we present a novel approach for the continuous focusing of such small-scale materials. First, we successfully focused fluorescent submicron polystyrene (PS) beads along equilibrium positions in microchannels through the addition of a small amount water-soluble polymer [500 ppm poly(ethylene oxide) (PEO)]. Lateral migration velocity significantly depends upon the viscoelastic effect (Weissenberg number: Wi) and the aspect ratio of particle size to channel height (a/h). Interestingly, focusing using viscoelastic flows was also observed for flexible DNA molecules (λ-DNA and T4-DNA), which have radii of gyration (R(g)) of approximately 0.69 μm and 1.5 μm, respectively. This small-scale material manipulation using medium viscoelasticity will contribute to the design of nanoparticle separation and genomic mapping devices.
authors: Department of Chemical Engineering, Ajou University, Suwon 443-749, Republic of Korea.
authors: Jae Young
authors: JY
authors: Kim
authors: Sung Won
authors: SW
authors: Ahn
authors: Sung Sik
authors: SS
authors: Lee
authors: Ju Min
authors: JM
authors: Kim
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004548:Elasticity; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014783:Viscosity
chemical_list: D003102:Colloids; D011137:Polystyrenes; D011092:Polyethylene Glycols; D004247:DNA