(315c) Continuous Passive Recovery of Hydrophilic Microparticles

A microfluidic method for the continuous passive separation of hydrogel (specifically polyethylene glycol or calcium-alginate) capsules containing viable mammalian cells from a non-polar matrix has been developed. The passive method achieves separation without exposing the encapsulated material or the capsules to significant mechanical forces, thereby preventing damage. To achieve passive separation, a microfluidic device with opposing channel walls of disparate hydrophobicity is used to stabilize co-laminar flow of immiscible fluids, in these cases various oils and an aqueous buffer. The disparity in hydrophobicity is accomplished by defining one length of the channel with a hydrogel. The chosen hydrogel was polyethylene glycol. Within the microfluidic device, the aqueous stream is stabilized by the hydrogel and the oil stream flows against a photo-curable adhesive that defines the opposing length of the channel. Passive separation with co-laminar flow has shown success in continuously separating micron scale capsules from an oil phase into an aqueous phase.                  

In addition to successful formation and separation of hydrogel microcapsules, the co-laminar flow device has also been demonstrated as an efficient means of breaking liquid-liquid emulsions.