Characterization of Mixing Performance Induced by Double Curved Passive Mixing Structures in Microfluidic Channels

Abstract

Functionalized sensor surfaces combined with microfluidic channels are becoming increasingly important in realizing efficient biosensing devices applicable to small sample volumes. Relaxing the limitations imposed by laminar flow of the microfluidic channels by passive mixing structures to enhance analyte mass transfer to the sensing area will further improve the performance of these devices. In this paper, we characterize the flow performance in a group of microfluidic flow channels with novel double curved passive mixing structures (DCMS) fabricated in the ceiling. The experimental strategy includes confocal imaging to monitor the stationary flow patterns downstream from the inlet where a fluorophore is included in one of the inlets in a Y-channel microfluidic device. Analyses of the fluorescence pattern projected both along the channel and transverse to the flow direction monitored details in the developing homogenization. The mixing index (MI) as a function of the channel length was found to be well accounted for by a double-exponential equilibration process, where the different parameters of the DCMS were found to affect the extent and length of the initial mixing component. The range of MI for a 1 cm channel length for the DCMS was 0.75–0.98, which is a range of MI comparable to micromixers with herringbone structures. Overall, this indicates that the DCMS is a high performing passive micromixer, but the sensitivity to geometric parameter values calls for the selection of certain values for the most efficient mixing.

Biocompatible bonding of a rigid off-stoichiometry thiol-ene-epoxy polymer microfluidic cartridge to a biofunctionalized silicon biosensor

“…A valuable feature for LOC biosensors is the integration of microfluidic structures for advanced flow manipulation. One example is the integration of passive mixing structures to enhance the mass transfer of analyte to the sensing area (Oevreeide et al 2021a(Oevreeide et al , 2021b. Feature dimensions are essential for such microfluidic structures.…”

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“…The MI was calculated according to the following equation (eqn (2)): 49 where N and N in are the number of pixels at the outlet and inlet of the considered channel, respectively, c i is the pixel intensity, and c is the mean pixel intensity in a given ROI. When MI = 0, the mixing is ineffective, whereas MI = 1 represents the complete homogenization.…”

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“…Passive micromixers have no energy requirements but instead utilize unique channel features such as curved or serpentine channel shapes [ 27 , 28 ], flow splitting and recombining obstacles [ 29 ], and baffles or cavities that force fluid paths that increase mixing efficiency [ 30 , 31 , 32 ]. Herringbone micromixer geometries, named for their resemblance to fish bone patterns, have been widely cited and adapted for efficient mixing and low-pressure drop in the microchannel, as the cavities do not directly impede flow [ 33 , 34 , 35 ].…”