A hydrodynamic focusing microchannel based on micro-weir shear lift force

Abstract

A novel microflow cytometer is proposed in which the particles are focused in the horizontal and vertical directions by means of the Saffman shear lift force generated within a micro-weir microchannel. The proposed device is fabricated on stress-relieved glass substrates and is characterized both numerically and experimentally using fluorescent particles with diameters of 5 lm and 10 lm, respectively. The numerical results show that the micro-weir structures confine the particle stream to the center of the microchannel without the need for a shear flow. Moreover, the experimental results show that the particles emerging from the micro-weir microchannel pass through the detection region in a one-by-one fashion. The focusing effect of the micro-weir microchannel is quantified by computing the normalized variance of the optical detection signal intensity. It is shown that the focusing performance of the micro-weir structure is equal to 99.76% and 99.57% for the 5-lm and 10-lm beads, respectively. Overall, the results presented in this study confirm that the proposed microcytometer enables the reliable sorting and counting of particles with different diameters. V C 2012 American Institute of Physics. [http://dx

High-throughput inertial particle focusing in a curved microchannel: Insights into the flow-rate regulation mechanism and process model

“…As a passive manipulation scheme, inertial particle focusing offers significant advantages such as continuous high-throughput processing, non-invasive manipulation without special labels, and simple operation without external fields. 1,2 It has therefore been employed as an important pretreatment strategy for wide-ranging applications such as size-based separation, [3][4][5][6] membrane-free filtration or enrichment, [7][8][9] sheathless microflow cytometry, [10][11][12] efficient solution exchange, 13 high-yield cell-in-droplet encapsulation, 14,15 and large population mechanical phenotyping. 16 With the prosperous development in novel biomedical applications of inertial focusing, the elucidation of the underlying mechanisms has attracted significant attention.…”

Making a hydrophoretic focuser tunable using a diaphragm

“…[3][4][5] Many of the microfluidic diagnosis devices involve particle or cell separation or focusing. [6][7][8][9][10][11] A number of techniques have been investigated for such a purpose, e.g., hydrodynamic filtration, [12][13][14] deterministic lateral displacement (DLD), [15][16][17][18][19] hydrophoresis, 20 and inertial microfluidics. 21,22 The performance of these methods is dictated by a lateral length scale of the microchannel, named as critical diameter, in relation of the particle size.…”

Hydrodynamic particle focusing design using fluid-particle interaction

“…1 The focusing devices can be categorized as either the active type that uses externally induced forces, [2][3][4][5][6][7][8][9][10][11][12][13] or the passive type that typically uses the hydrodynamic fluid effects. [14][15][16][17][18][19][20][21][22][23][24] Because of the advantages on the simple structure, potential for integration, label free, and biology compatibility, many passive focusing effects have been used in microfluidic devices, such as the sheath flow effect, the hydrodymatic effect, 25,26 the inertial and dean effect, [20][21][22][23][24]27 the hydrophoretic effect, 15,16 etc. The sheath flow method requires more than one input flow at the inlet port and a relatively accurate flow control in order to push the flow with particles existing in the specified position of microfluidic channel.…”