Characterization of microfluidic mixing and reaction in microchannels via analysis of cross-sectional patterns

Abstract

For the diagnosis of biochemical reactions, the investigation of microflow behavior, and the confirmation of simulation results in microfluidics, experimentally quantitative measurements are indispensable. To characterize the mixing and reaction of fluids in microchannel devices, we propose a mixing quality index ͑M qi ͒ to quantify the cross-sectional patterns ͑also called mixing patterns͒ of fluids, captured with a confocal-fluorescence microscope ͑CFM͒. The operating parameters of the CFM for quantification were carefully tested. We analyzed mixing patterns, flow advection, and mass exchange of fluids in the devices with overlapping channels of two kinds. The mixing length of the two devices derived from the analysis of M qi is demonstrated to be more precise than that estimated with a commonly applied method of blending dye liquors. By means of fluorescence resonance-energy transfer ͑FRET͒, we monitored the hybridization of two complementary oligonucleotides ͑a FRET pair͒ in the devices. The captured patterns reveal that hybridization is a progressive process along the downstream channel. The FRET reaction and the hybridization period were characterized through quantification of the reaction patterns. This analytical approach is a promising diagnostic tool that is applicable to the real-time analysis of biochemical and chemical reactions such as polymerase chain reaction ͑PCR͒, catalytic, or synthetic processes in microfluidic devices.

Mixing in microfluidic devices and enhancement methods

“…Fluorescent particles or fluids are also used in conjunction with a microscope to quantitatively characterize the mixing [21, 22]. In a similar manner, 3D flow patterns can be constructed using confocal-fluorescence microscopy [23]. Furthermore, experimenters can mix reactive components and track the reaction along the channel length, which can be correlated to the efficiency of mixing enhancements [24].…”

Analysis of the Diffusion Process by pH Indicator in Microfluidic Chips for Liposome Production

“…Different methods for quantifying mixing in microfluidics have been presented; these are generally based on the acquisition of microscopic images of two or more colored or fluorescently labelled liquids, followed by quantification of mixing efficiency using simple mathematical functions. Examples of dyes employed are food dyes or stains for biological microscopy [ 13 ], or fluorescent dyes such as fluorescein [ 14 , 15 ].…”

Microfluidic techniques for separation of bacterial cells via taxis

“…Control of mixing inside a microfluidic channel is desirable for biological and chemical assays, as well as microreactors for industrial applications [68]. Passive methods using channel geometries or active methods using mechanical valves can be integrated into a microfluidic chip to promote mixing [69].…”