(62h) Calcium-Alginate Capsule Formation and Separation 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 mono-disperse droplets in a microfluidic device is used to form calcium-alginate capsules through a suspension polymerization in an oil solution from aqueous droplets of calcium chloride and sodium alginate. Calcium-alginate capsules have many potential uses, such as immunoisolation of cells, microencapsulation of active drug ingredients, and encapsulation of bitter agents in food or beverage products. Capsule formation is accomplished through fusion of a sodium alginate droplet and a calcium chloride droplet. The high surface tension between the droplet of calcium chloride and sodium alginate necessitates the use of the surfactant sodium dodecyl sulfate (SDS) and a soft lithography device with a judiciously designed geometry. After creating the capsules, it is necessary to separate them out of the oil solution and into an aqueous solution. A common method of separation is centrifugation, which can damage both the capsules and the cells inside. The use of a microfluidic device with channel walls of disparate hydrophobicity is used to stabilize co-laminar flow of an oil phase and an aqueous phase. The disparity of hydrophobicity is accomplished by defining one side of the microfluidic device with the hydrogel poly (ethylglycene) (PEG), which adheres to the glass surface through the use of 3-(trichlorosilyl)-propyl methacrylate (TPM). Due to the difference in surface energy within the channel, the aqueous stream is stabilized near PEG-DA and the oil stream is stabilized near a hydrophobic resin (optical adhesive). The technique of passive separation using co-laminar flow has shown promising results in separating the calcium-alginate capsules from the oil phase and into the aqueous phase. The separation device has also shown potential for applications in extraction, specifically extracting a dye from a hydrophobic fluid into a hydrophilic fluid during co-laminar flow within the channel.