Integrated droplet microfluidic device for magnetic particles handling: Application to DNA size selection in NGS libraries preparation

Development of a Droplet Microfluidics Device Based on Integrated Soft Magnets and Fluidic Capacitor for Passive Extraction and Redispersion of Functionalized Magnetic Particles

“…Finally, according to the investigated Φ, a maximum processing speed of about 17 mm s −1 can be achieved by our system for the whole extraction and redispersion process. Importantly, the presented system allows performances comparable with the previous active configuration9 but exploiting a passive strategy therefore no tuning is required as a function of the processing velocity.…”

“…During the experiment, an external permanent magnet is placed near the device to magnetize the integrated soft magnets, as shown in Figure 1a,b. We present here an extension of a previous model,9 in which, using this configuration, the magnetic field streamlines result focalized in the side channel portion delimited by the microstructures (see Figure a). This leads to a locally higher magnetic flux density gradient ( ∇B ) that causes a magnetic force ( F mag ) driving the magnetic particles in the capture region.…”

“…Data analysis was performed by ImageJ software and LabVIEW (National Instrument) home‐made scripts, following the workflow described in ref. 9. The carryover of supernatant in the extracted cluster was estimated by considering the interstitial volume between packed beads 33…”

“…The first examples proposed rely on the splitting of a parent droplet in two daughter droplets at a T‐junction, while an external magnet allows the enrichment of the magnetic particles in one of them 7,8. This process is characterized by a complete recovery of the particles present in the parent droplet (high extraction efficiency9); however, the symmetric splitting strategy limits the purification efficiency (≃50%), which is defined as the depletion rate of the original matrix in the final purified solution 9. Devoted strategies for inducing an asymmetric droplet splitting were also proposed, which can be divided into passive or active control methods.…”

“…Consequently, the implementation of multistep workflows would require devoted merging modules 15,16. We recently proposed an active control method consisting in a device allowing the tuning of the droplet deformation at a T‐junction by an external pressure–based system, coupled with integrated soft magnets for particles handling 9. Together with high purification rate, this approach guarantees particles' extraction from a droplet and redispersion in a different one, being suitable for multistep protocols.…”