Inertial microfluidics for sheath-less high-throughput flow cytometry

Abstract

Flow cytometer is a powerful single cell analysis tool that allows multi-parametric study of suspended cells. Most commercial flow cytometers available today are bulky, expensive instruments requiring high maintenance costs and specially trained personnel for operation. Hence, there is a need to develop a low cost, portable alternative that will aid in making this powerful research tool more accessible. In this paper we describe a sheath-less, on-chip flow cytometry system based on the principle of Dean coupled inertial microfluidics. The design takes advantage of the Dean drag and inertial lift forces acting on particles flowing through a spiral microchannel to focus them in 3-D at a single position across the microchannel cross-section. Unlike the previously reported micro-flow cytometers, the developed system relies entirely on the microchannel geometry for particle focusing, eliminating the need for complex microchannel designs and additional microfluidic plumbing associated with sheath-based techniques. In this work, a 10-loop spiral microchannel 100 microm wide and 50 microm high was used to focus 6 microm particles in 3-D. The focused particle stream was detected with a laser induced fluorescence (LIF) setup. The microfluidic system was shown to have a high throughput of 2,100 particles/sec. Finally, the viability of the developed technique for cell counting was demonstrated using SH-SY5Y neuroblastoma cells. The passive focusing principle and the planar nature of the described design will permit easy integration with existing lab-on-a-chip (LOC) systems.

Vortex-aided inertial microfluidic device for continuous particle separation with high size-selectivity, efficiency, and purity

“…5,6 These forces cause cells to migrate across streamlines and order in equilibrium positions based on their size, leading to label-free cell separation, purification and enrichment in a microfluidic device with designed geometries. 7 Applications for separation of cells (erythrocytes/leukocytes, [8][9][10] neuronal cells, 6 cancer cells 11 ), flow cytometry, [12][13][14] and rare cell enrichment [15][16][17] have been developed achieving passive cell and particle manipulation with extremely high throughput.…”

Integrated optical waveguides and inertial focussing microfluidics in silica for microflow cytometry applications

“…Beads were also well confined parallel to the long face of the channel so that all beads flowed through the excitation beam positioned halfway up the height of the channel. The measured fluorescence signal CV for calibration beads of 26% was slightly higher than another inertial focussing based cytometer with external optics [39]. The use of higher flow rates to further confine the flow streams and an on chip fluorescence collection system to minimise the effect of vibration are expected to further reduce the fluorescence signal variation.…”

“…The distribution is represented by a median fluorescence energy of 658 fJ. At the flow rate used, of 0.2 µl/s, the coefficient of variation was 26% which is slightly higher than a inertial focussing microflow cytometer with external optics [39]. It is expected that higher flow rates would lead to further vertical confinement and reduce the fluorescence signal CV further as inertial lift forces increase with flow velocity causing faster migration of beads to equilibrium positions.…”

High‐Throughput Inertial Focusing of Micrometer‐ and Sub‐Micrometer‐Sized Particles Separation

“…When the measured FWHM is less than twice the particle diameter, the particle stream is defined as focused 16. There is a common view that it is difficult to precisely focus microparticles in asymmetric serpentine channels36 because the steak widths are often two to three times the particle diameter in size 27, 37. However, the results from this study show that the streak width is essentially the same as the particle diameter at low particle concentrations, strongly indicating that the suspension flows single file along a pathline.…”