Abstract
Microalgae – unicellular photosynthetic organisms – have received increasing attention for their ability to biologically convert CO2 into valuable products. The commercial use of microalgae requires screening strains to improve the biomass productivity to achieve a high-throughput. Here, we developed a microfluidic method that uses a magnetic field to separate the microdroplets containing different concentrations of microalgal cells. The separation efficiency is maximized using the following parameters that influence the amount of lateral displacement of the microdroplets: magnetic nanoparticle concentration, flow rate of droplets, x- and y-axis location of the magnet, and diameter of the droplets. Consequently, 91.90% of empty, 87.12% of low-, and 90.66% of high-density droplets could be separated into different outlets through simple manipulation of the magnetic field in the microfluidic device. These results indicate that cell density-based separation of microdroplets using a magnetic force can provide a promising platform to isolate microalgal species with a high growth performance.
Highlights
Global energy demand has steadily increased as the world population increases and living standards improve
We developed a microfluidic system that uses a magnetic force to separate the three kinds of magnetic microdroplets containing a different number of microalgal cells
This density-based magnetophoretic sorting system has been made possible for the first time using a featured design of microchannel in microfluidic device, which enables distinguishing micrometer-scale difference in lateral displacement
Summary
Global energy demand has steadily increased as the world population increases and living standards improve. Droplet-based microfluidics can be utilized to conduct parallel, high-throughput experiments because microdroplets can be generated at frequency of up to 10 kHz23, 24 Based on these advantages, it is possible to utilize microdroplets as a bioreactor to simultaneously cultivate different microalgal species[25,26,27]. Efficient sorting technology to separate microdroplets with different cell densities can be a promising solution to quickly isolate fast-growing microalgal strains. Several studies have been carried out on cell density-based separation of microdroplets using chlorophyll fluorescence[28] or alginate beads using a standing surface acoustic wave (SSAW)[29] in microfluidic devices These microfluidic approaches require a complex device design and a fabrication process to integrate the electrodes, piezoelectric substrates, and additional equipment, including a signal generator, amplifier, and DC power supply[28,29,30]. This microfluidic platform can be used to separate empty, low-, and high-density microdroplets with an efficiency higher than 90%
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