Continuous Formation and Separation of Calcium-Alginate Capsules Containing Viable Mammalian Cells in Microfluidic Devices

Microfluidic devices can be used for many applications, including the formation of well-controlled emulsions. In this study, the capability to continuously create monodisperse droplets in a microfluidic device was used to form calcium-alginate capsules.Calcium-alginate capsules have many potential uses, such as immunoisolation of cells and microencapsulation of active drug ingredients or bitter agents in food or beverage products. The gelation of calcium-alginate capsules is achieved by crosslinking sodiumalginate with calcium ions. Calcium ions dissociated from calcium carbonate due to diffusion of acetic acid from a sunflower oil phase into an aqueous droplet containing sodium-alginate and calcium carbonate. After gelation, the capsules were separated from the continuous oil phase into an aqueous solution for use in biological applications. Typically, capsules are separated bycentrifugation, which can damage both the capsules and the encapsulated material. A passive method achieves separation without exposing the encapsulated material or the capsules to large mechanical forces, thereby preventing damage. To achieve passiveseparation, the use of a microfluidic device with opposing channel wa hydrophobicity was used to stabilize co-laminar flow of im of hydrophobicity is accomplished by defining one length of the channel with a hydrogel. The chosen hydrogel was poly (ethylene glycol) diacrylate, which adheres to the glass surface through the use of self-assembled monolayer of 3-(trichlorosilyl)-propyl methacrylate. Due to the difference in surface energy within the channel, the aqueous stream is stabilized near a hydrogel and the oil stream is stabilized near the thiolene based optical adhesive defining the opposing length of the channel. Passive separation with co-laminar flow has shown success in continuously separating calcium-alginatecapsules from an oil phase into an aqueous phase. In addition to successful formation and separation of calcium alginate capsules,encapsulation of Latex micro-beads and viable mammalian cells has been achieved. The viability of encapsulated mammalian cells was determined using a live/dead stain. The co-laminar flow device has also been demonstrated as a means of separating liquid-liquidemulsions.

Efficient Liquid Liquid Extraction By Emulsion Formation and Separation in Robust Milli-Fluidic Devices

Conventional liquid liquid extraction (LLE) methods require large volumes of fluids to achieve the desired mass transfer of a solute, which is unsuitable for systems dealing with a low volume or high value product. An alternative to these methods is to scale down the process. Millifluidic devices share many of the benefits of microfluidic systems, including low fluid volumes, increased interfacial area-to-volume ratio, and predictability. A robust millifluidic device was created from acrylic, glass, and aluminum. The channel is lined with a hydrogel cured in the bottom half of the device channel. This hydrogel stabilizes co-current laminar flow of immiscible organic and aqueous phases. Mass transfer of the solute occurs across the interface of these contacting phases. Using a y-junction, an aqueous emulsion is created in an organic phase. The emulsion travels through a length of tubing and then enters the co-current laminar flow device, where the emulsion is broken and each phase can be collected separately. The inclusion of this emulsion formation and separation increases the contact area between the organic and aqueous phases, therefore increasing the area over which mass transfer can occur. Using this design, 95% extraction efficiency was obtained, where 100% is represented by equilibrium. By continuing to explore this LLE process, the process can be optimized and with better understanding may be more accurately modeled. This system has the potential to scale up to the industrial level and provide the efficient extraction required with low fluid volumes and a well-behaved system.