Fig.6 . Summary of state of art microfluidics-based methods for bacteria separation from blood. In general, there is a trade-off between separation efficiency and sample throughput using both active and passive methods. Our current work for the different diluted blood samples is shown in red having the highest efficiency ( > 80% ) using single passage in a single chip.
One way to increase the throughput in our current setup is via parallelization. We have previously presented on a highly scalable, lithography-defined microfabrication method for passive size-based particle separation56. For spiral design, it is straightforward to stack the devices vertically, as reported by Warkiani., et al 57. As a proof of principle, we tested stacking two spiral channels and tested particle separation (supplementary Fig.S3). At a total flow rate of 3 mL/min, complete separation of 1µm and 7µm particles is shown in supplementary Fig.S3. Future studies should focus on expanding the bacteria strains, including common pathogenic strains for clinical implementation. While outside the scope of this paper, we have initiated the work on stacked spiral devices for clinical implementation of the stand-alone sample preparation module. We anticipate the method presented here to be of high value in clinical sample preparation applications for both nucleic acid based molecular diagnostics and phenotypic analysis.