Beating Poisson stochastic particle encapsulation in flow-focusing microfluidic devices using viscoelastic liquids

Abstract

The encapsulation and co-encapsulation of particles in microfluidic flows is essential in applications related to single-cell analysis and material synthesis. However, the whole encapsulation process is stochastic in nature, and its efficiency is limited by the so-called Poisson limit. We here demonstrate particle encapsulation and co-encapsulation in microfluidic devices having flow-focusing geometries with efficiency up to 2-folds larger than the stochastic limit imposed by the Poisson statistics. To this aim, we exploited the recently observed phenomenon of particle train formation in viscoelastic liquids, so that particles could approach the encapsulation area with a constant frequency that was subsequently synchronised to the constant frequency of droplet formation. We also developed a simplified expression based on the experimental results that can guide optimal design of the microfluidic encapsulation system. Finally, we report the first experimental evidence of viscoelastic co-encapsulation of particles coming from different streams.

Continuous Manufacturing of Microfluidic Fibers Embedded with Ordered Microparticles via Ionic Gelation

“…Briefly, equally spaced particles approach the encapsulation area with a constant frequency (at variance with the case when particles are not ordered), which is synchronized to the frequency of droplet formation (which is constant). By taking advantage of both the viscoelastic ordering 26 , 36 , 40 and the controlled encapsulation phenomena 50 , 51 in conjunction with the fiber formation presented here, we foresee the potential for the generation of other materials via the same principles. It is also worth mentioning that particle ordering and controlled encapsulation can also be achieved in purely inertial flow.…”

“…Briefly, equally spaced particles approach the encapsulation area with a constant frequency (at variance with the case when particles are not ordered), which is synchronized to the frequency of droplet formation (which is constant). By taking advantage of both the viscoelastic ordering ,, and the controlled encapsulation phenomena , in conjunction with the fiber formation presented here, we foresee the potential for the generation of other materials via the same principles. It is also worth mentioning that particle ordering and controlled encapsulation can also be achieved in purely inertial flow. ,, However, the addition of polymer solutions has two strong advantages: (i) in viscoelastic ordering, particles are ordered on the channel centerline, while in the inertial ordering, they are generally ordered near the channel wall and on multiple lines and (ii) the addition of polymer solutions increase the elastic properties of the fibers, which is often desirable.…”