Abstract
Ferrofluid-based micromixers have been widely used for a myriad of microfluidic industrial applications in biochemical engineering, food processing, and detection/analytical processes. However, complete mixing in micromixers is extremely time-consuming and requires very long microchannels due to laminar flow. In this paper, we developed an effective and low-cost microfluidic device integrated with microscale magnets manufactured with neodymium (NdFeB) powders and polydimethylsiloxane (PDMS) to achieve rapid micromixing between ferrofluid and buffer flow. Experiments were conducted systematically to investigate the effect of flow rate, concentration of the ferrofluid, and micromagnet NdFeB:PDMS mass ratio on the mixing performance. It was found that mixing is more efficient with lower total flow rates and higher ferrofluid concentration, which generate greater magnetic forces acting on both streamwise and lateral directions to increase the intermixing of the fluids within a longer residence time. Numerical models were also developed to simulate the mixing process in the microchannel under the same conditions and the simulation results indicated excellent agreements with the experimental data on mixing performance. Combining experimental measurements and numerical simulations, this study demonstrates a simple yet effective method to realize rapid mixing for lab-on-chip systems.
Highlights
Microfluidics is the study pertaining the design and manufacturing of small devices that embody tiny channels to enable precise control and manipulation of fluids at the micro scale, typically ten to hundreds of microns [1,2]
This section discusses the effect of total flow rate, ferrofluid concentration, and magnet mass ratio of NdFeB:PDMS on the mixing efficiency inside the fluidic channel from experiments
We proposed a microfluidic device that can achieve the rapid mixing of ferrofluid and distilled water by utilizing a miniaturized and integrated microscale magnet
Summary
Microfluidics is the study pertaining the design and manufacturing of small devices that embody tiny channels to enable precise control and manipulation of fluids at the micro scale, typically ten to hundreds of microns [1,2]. Mixing of reagents and analytes is one of the most important applications and an essential step in microfluidic devices for pre-processing, dilution, or inducing reactions between samples and reagent [9]. Fluids containing molecules such as proteins and DNAs with small diffusion coefficients require longer channels which in turn takes a longer time for complete mixing [10,11]. This gives rise to the need for rapid mixing in microfluidic devices, especially those involving fluids of large molecules, to save mixing time, shorten the length of channels, and ensure complete mixing [12,13]
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