Field-Flow Fractionation and Hydrodynamic Chromatography on a Microfluidic Chip

Abstract

We present gravitational field-flow fractionation and hydrodynamic chromatography of colloids eluting through 18 μm microchannels. Using video microscopy and mesoscopic simulations, we investigate the average retention ratio of colloids with both a large specific weight and neutral buoyancy. We consider the entire range of colloid sizes, including particles that barely fit in the microchannel and nanoscopic particles. Ideal theory predicts four operational modes, from hydrodynamic chromatography to Faxén-mode field-flow fractionation. We experimentally demonstrate, for the first time, the existence of the Faxén-mode field-flow fractionation and the transition from hydrodynamic chromatography to normal-mode field-flow fractionation. Furthermore, video microscopy and simulations show that the retention ratios are largely reduced above the steric-inversion point, causing the variation of the retention ratio in the steric- and Faxén-mode regimes to be suppressed due to increased drag. We demonstrate that theory can accurately predict retention ratios if hydrodynamic interactions with the microchannel walls (wall drag) are added to the ideal theory. Rather than limiting the applicability, these effects allow the microfluidic channel size to be tuned to ensure high selectivity. Our findings indicate that particle velocimetry methods must account for the wall-induced lag when determining flow rates in highly confining systems.

Retention ratio and nonequilibrium bandspreading in asymmetrical flow field-flow fractionation

“…(13) as α approaches zero, as expected, but the wide range of α makes it difficult to discern the difference between the solutions when α<λ≪1, which is the region with which we are concerned here. Shendruk et al [47] later presented experimental results supporting the model, but again, the experiments were not relevant to the typical range of stericcorrected normal mode FFF.…”

Microfluidic device for sheathless particle focusing and separation using a viscoelastic fluid

“…Microfluidic separation techniques can be categorized into two operating modes in general-batch mode and continuous flow mode. In batch mode, a prolonged operation time and complicated fluidic control are required [10,11]. These drawbacks can be circumvented in the continuous flow mode separation.…”

Continuous-flow Size-based Separation of Microparticles by Microchip Electromagnetophoresis

“…[1][2][3] Recently, various techniques of microparticle separation, based on electrophoresis, 4,5 magnetophoresis, 6,7 dielectrophoresis (DEP), [8][9][10] acoustophoresis, 11,12 dean flow, 13 pinched flow fractionation (PFF), 14 field-flow fractionation (FFF), [15][16][17][18] and split-flow thin (SPLITT) fractionation, [19][20][21] have been demonstrated. These techniques have been effectively used for separation in combination with the microchip system.…”