Experimental and numerical investigation into micro‐flow cytometer with 3‐D hydrodynamic focusing effect and micro‐weir structure

Abstract

This study presents a novel 3-D hydrodynamic focusing technique for micro-flow cytometers. In the proposed approach, the sample stream is compressed initially in the horizontal direction by a set of sheath flows such that it is constrained to the central region of the microchannel and is then focused in the vertical direction by a second pair of sheath flows. Thereafter, the focused sample stream passes over a micro-weir structure positioned directly beneath an optical detection system to capture polystyrene beads fluorescent signal. The microchannel configuration and operational parameters are optimized by performing a series of numerical simulations. An experimental investigation is then performed using a micro-flow cytometer fabricated using conventional micro-electro-mechanical systems techniques and an isotropic wet etching method. The results indicate that the two sets of sheath flows successfully constrain the sample stream within a narrow, well-defined region of the microchannel. Furthermore, the micro-weir structure prompts the separation of a mixed sample of 5 and 10 microm polystyrene beads in the vertical direction and ensures that the beads flow through the detection region of the microchannel in a sequential fashion and can therefore be reliably detected and counted.

Microfluidic impedance‐based flow cytometry

“…Tsai et al (88,89) combined lateral sheath focusing with vertical focusing, using a weir structure to separate particles directly over the detection area.…”

High-performance microfluidic rectifier based on sudden expansion channel with embedded block structure

“…Finally, the pressure and velocity fields were decoupled using the semi-implicit method for pressurelinked equations (SIMPLE). 51,52 …”

“…Many functional microfluidic devices have been developed to perform such diverse tasks as sample pre-treatment and injection, polymerase chain reaction, species mixing, and cell/particle sorting and counting. [9][10][11][12][13][14][15][16] In such devices, the species are typically manipulated using external devices such as pumps, valves, or actuators. [17][18][19][20][21][22][23][24] In many microfluidic devices, microvalves are combined with a micropump in order to achieve uni-directional species flow.…”

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

“…Microflow cytometers provide a high-throughput means of sorting and counting cells/particles and are used in a wide variety of biomedical and industrial applications, including clinical hematology diagnosis, bacteria analysis, and gene diagnosis. [15][16][17][18][19][20] In a typical microflow cytometer, the cells/particles are injected into an electrolyte solution and are then focused in the horizontal plane by two sheath flows such that they pass through the detection region of the device in a single line fashion. 21,22 Fu et al 23 developed an electrokinetically driven microflow cytometer in which the sample was focused in the horizontal a) Author to whom correspondence should be addressed.…”